SECTIONS:

-- Taxonomy
-- Size
-- Colour
-- Distribution & Population Structure
-- Ageing & Longevity
-- Sexing
-- Activity
-- Habitat
-- Territory & Home Range
-- Survival, Mortality & Predators
-- Food & Feeding Behaviour
-- Breeding Biology
-- Antlers
-- Behaviour & Social Structure
        -- Stag Groups
        -- Hind Groups
        -- Communication
-- Interaction with Humans
        -- Numbers & Management
        -- Parasites & Diseases
        -- Deer Parks & Farms
        -- Road Traffic Collisions
        -- Genetic Diversity & Hybridization

 

The Red deer has a long history in Britain – one of only two native deer species in the UK, it’s a beast highly prized by hunters, naturalists, artists, poets and photographers alike.   Renowned Scottish artist Archibald Thorburn summed up the situation nicely in his 1920 book British Mammals, in which he wrote that the Red deer “is unquestionably the grandest wild animal we now possess in the British Islands.”   That which follows is a summary of Red deer natural history.   Certain aspects of the natural history common to all deer (e.g. antler growth and formation, collisions with vehicles, chronic wasting disease) have been split from the individual overviews and placed into their own QA – this is partly to avoid repetition but also to allow more detailed coverage of the topics.   A summary of the more general aspects of the biology, ecology and behaviour of Britain’s deer species can be found elsewhere on this site.

Taxonomy: Deer classification is a contentious subject, with disagreement over where the animals sit in relation to other mammals (namely whether or not they should be grouped with the whales and dolphins) as well as how many species and/or subspecies should be formally recognised.   Nonetheless, there is agreement that the majority of deer (i.e. all those except the Musk deer of the south Asian mountains) can be grouped within a single family: the Cervidae.   The Cervidae holds two subfamilies: the Old World deer of the Cervinae and the New World deer of the Capreolinae.   Within the Cervinae sit two tribes: the Cervini (“true deer”) and the Muntiancini (muntjacs).   It is the Cervini tribe that interests us here – it contains four genera: Axis; Dama; Rucervus; and Cervus, which holds the Red deer in its various forms.   We now arrive at something of a taxonomical minefield!

Cervus is, to say the least, a contentious genus and there is much debate as to the number of species, and especially the number of subspecies, it contains.   I have opted to follow the bulk of the molecular data here and as such consider there to be 10 species within the Cervus genus (12 if recent molecular data are confirmed – see below).   I should mention that the close relationship between members of Cervus means that there is apparently a terrific potential for hybridization, which serves to further confuse the allocation of species within this genus.   Fertile hybrids of Sika (C. nippon) and Red are known from the wild, while two papers to the Journal of Heredity during 1997 demonstrated that successful conception can result from crossing Red deer with both Sambar (C. unicolor) and Pere David’s (Cervus davidianus) deer, although both studies used artificial insemination and success rates were low.   Indeed, it’s worth remembering that what happens in captivity and what happens in the wild may be very different!

The majority of Cervus species have been fairly well defined, but there are two in particular that have caused (indeed, are still a source of) much controversy – debate rages over whether the wapiti and Red deer should be considered the same, or distinct, species.   The wapiti range over much of North America and eastern Asia and are superficially similar to the Red deer of Europe and Asia (an area collectively termed “Eurasia”).   (Incidentally, the wapiti are often referred to as “elk” in North America, but should not be confused with the European “elk”, or Moose, Alces alces!)   Traditionally, many authors have chosen to lump wapiti within (i.e. as a subspecies of) the Red deer because, despite various anatomical, biochemical, ecological, behavioural and (more recently) genetic differences, wapiti are able to hybridize successfully -- i.e. to produce fertile offspring -- with contiguous populations of Red deer.   Consequently, many scientists prefer to think of Cervus elaphus as a “superspecies” or “ring species”, containing a number of very closely-related animals that can all be considered Red deer.   However, not everybody agrees.

The idea that Red deer and wapiti are distinct species is not a new one; some of the first suggestions were made in 1737 and wapitis were first elevated to the species level by German naturalist Georg Heinrich Borowski in 1780.   In 1806 Pennsylvanian-born naturalist and physician Benjamin Smith Barton suggested that North American elk and Red deer from Europe were sufficiently different to be considered different species and proposed the name wapiti, meaning “white rump”, for the North American elk.   Since then, the wapiti has been the subject of much taxonomic yo-yoing, being moved between a full species, Cervus canadensis, and a subspecies of Red deer (Cervus elaphus canadensis).   Work by taxonomists from the mid-1980s to the mid-1990s led to the splitting of wapiti and Red deer based on data from skeletal measurements, protein assays and haemoglobin morphology.   However, in their review of the situation in 1989, Patrick Lowe and Andrew Gardiner concluded that, from their analysis of nearly 300 deer skulls, although some morphological variation exists supporting the separation at the subspecies level, “there appears to be no justification for distinguishing between them at the species level”.

In 2001, Instituto Nazionale per la Fauna Selvatica (Italy) taxonomist Ettore Randi and four colleagues published a study in the journal Animal Conservation supporting the idea that European Red deer should be split from the North American animals.   The study looked at mitrochondrial DNA (mtDNA) sequences from 13 species of deer (seven from the Cervus genus) and found that the wapiti formed a clade, as distinct from European Red deer, which is nestled with the Sika deer (Cervus nippon) on their cladogram.   In their summary, the researchers write:

“Cervus elaphus includes two divergent clades that must be referred to as species elaphus (European elaphoid deer) and canadensis (Eurasian & North American wapitoid deer).”

A large study, published in the journal Molecular Phylogenetics and Evolution during 2004, by Technical University Munich-Weihenstephan (in Germany) taxonomist Christian Ludt and three colleagues, looked at a particular gene carried on the mtDNA of 51 populations of deer spanning the entire distribution of Cervus.   The geneticists found that they could identify two distinct groups: an eastern group (comprised of Cervus canadensis and several subspecies) and a western group (containing Cervus elaphus), which split from each other about 7 million years ago.   Most subsequent molecular studies looking at deer taxonomy support the division of wapiti and Red deer into separate species.   With Cervus canadensis removed from the equation, we’re left with our species of interest: The European Red deer, Cervus elaphus (henceforth referred to as the Red deer).

Red deer, as we currently think of them, may actually be as many as three separate species, according to the cytochrome analysis performed by Christian Pitra and his colleagues published in the journal Molecular Phylogentics and Evolution during 2004.   I won’t go into much detail about the findings here, but suffice to say that Dr Pitra and his team found molecular evidence to suggest that Red deer from Central Asia and those from North Africa and Corsica-Sardinia may represent species as distinct from Cervus elaphus (Cervus yarkandensis and Cervus corsicanus, respectively).   The findings of Dr Pitra and his colleagues require additional study and no such split has been widely accepted.

The terrific variation observed in Red deer throughout their range has lead to the description of many potential subspecies.   In his Whitehead Encyclopedia of Deer, G Kenneth Whitehead lists 12 sub-species (the highest number I’ve come across is 22) including Cervus elaphus hippelaphus (the Carpathian Red from central Europe), Cervus elaphus hispanicus (Spain & Portugal), Cervus elaphus atlanticus (Norway) and the type specimen (i.e. that first described by taxonomists) Cervus elaphus elaphus (Sweden).   The variations between these subspecies range from the subtle to the striking.   Carpathian stags, for example, may weigh in at some 500kg (1100 lbs), while the Corsican Red (Cervus elaphus corsicanus) typically reaches less than 100kg (220 lbs); Red stags in Britain and Norway sport thick, dark neck manes, while those in Spain fail to develop any trace of a mane.

Coat colour and differences in the size and shape of the antlers are also often among the characteristics used to distinguish subspecies.   Unfortunately, the majority of these traits are not good taxonomic indicators, because they’re readily influenced by the environment – arguably this is especially true for body size and antler growth, both of which can be severely limited in habitats with poor grazing/browsing, even though antler development appears deeply rooted in the animal’s genetics.   Consequently, the subspecific division of the Red deer remains a controversial topic.   I don’t wish to get too tied up in the debates over which are valid subspecies and why, but I will briefly cover the story of the subspecies considered by many to be the native stock of Britain: Cervus elaphus scoticus.

In 1906, Swedish zoologist Axel Lönnberg (who often went by his middle name Einar) published a paper in the journal Arkiv för Zoologi about the geographic races of Red deer.   In the paper Dr Lönnberg compared the skull anatomy of Red deer collected from various parts of its range and proposed several of the 12-or-so subspecies still in contention today.   In particular, Dr Lönnberg describes the skulls of two stags killed in Glenquoich Forest in Invernesshire, north-west Scotland.   The skulls displayed some features in common with Swedish (C. e. elaphus) skulls and others in common with Norwegian (C. e. atlanticus) skulls, but could not be confidently allied with either subspecies.   In his appraisal, Dr Lönnberg wrote of the Scottish deer:

“It is accordingly neither identical with the typical race of southern Sweden nor with the race of western Norway and most probably forms an independent geographic race or subspecies which suitably may be termed scoticus.”

Since Dr Lönnberg’s comparisons, the Scottish Red deer has been widely referred to as C. e. scoticus.   However, more recently, several studies have suggested that there may be far fewer than 12 subspecies and have cast doubt on the validity of the Scottish Red as a valid subspecies.   In a major review of Red deer taxonomy published in the Journal of Zoology during 1974, Patrick Lowe and Andrew Gardiner found that C. elaphus exhibits a high degree of morphological similarity between the animals across their range.   Generally-speaking, it is considered that in order for two individuals to be considered for subspecific status, there should be a maximum of 10% overlap in physical characteristics – in other words, they should be at least 90% different from each other.   Drs Lowe and Gardiner examined the skulls of 10 of the 19 subspecies of Red deer listed by John Ellerman and Sir Charles Morrison-Scott in their 1951 Checklist of Palaearctic and Indian Mammals 1758 to 1946, examining 16 variables of skull size and shape and subjecting the data to three separate statistical analyses.   The taxonomists did find evidence for two distinct, yet “visually identical”, ‘forms’ of Red deer living wild in Britain (one in Scotland, Ireland and northern England, presumed native, and another of apparent park origin found through the rest of England), but only atlanticus overlapped with the other subspecies by less than 10%, while scoticus was 60% similar to the hippelaphus subspecies from Europe and Scandinavia.   Overall, the biologists failed to find support for more than a single subspecies of Red deer in northern Europe, the type species Cervus elaphus elaphus and in their conclusion they wrote:

“None of the features of the skull measured for this study support the concept of subspeciation in red deer, there being no discontinuities between the various subspecies sampled.”

Genetic data have contributed greatly to our understanding of subspecific relationships among deer, although the debate is far from settled.   In a 1983 paper to the journal Heredity, Ulf Gyllensten and three colleagues presented data from nearly 600 tissue samples on the genetic diversity of four proposed subspecies from Britain, Germany, Norway and Sweden.   Dr Gyllensten and his team found what they called “a major genetic dichotomy” between British and Norwegian deer on the one hand and Swedish and German deer on the other.   In other words, scoticus and atlanticus form a group that are more closely related to each other than either is to elaphus or some hippelaphus specimens.   This would suggest that even if all four subspecies aren’t valid, a subspecific divide may exist between Swedish/German and British/Norwegian deer.

More recently, Christian Ludt and his team presented their data from a special type of protein called a cytochrome.   In addition to the east-west divide uncovered by the German biologists (see above), they failed to find any support for the subspecies atlanticus, brauneri, elaphus, hippelaphus, hispanicus and scoticus within the western group – in other words, they couldn’t distinguish these specimens from the “type specimen”, C. e. elaphus.   Conversely, Dr Pitra and his team found more support for some of the subspecies, but didn’t include samples from either C. e. elaphus or C. e. scoticus.   Unfortunately, as far as I am aware, at the time of writing this is as far as the situation has been taken, so we remain in something of a hiatus.

Despite the conflicting data, many authors consider that the remaining native stocks of Red deer in Britain are represented by a few populations of Cervus elaphus scoticus residing on the Scottish hillsides and in parts of north-west England.   Overall, I feel it is probably best to avoid reference to subspecies until the situation is at least closer to resolution.   Consequently, the following classification scheme works down to the species level and applies to Red deer throughout their range (including the UK).   While I have split out the wapiti from the Red deer, the remainder of this overview will draw on research and data on Red deer from throughout their range, irrespective of proposed subspecies, but will focus on research carried out on British populations where available.   Similarly I will attempt to refer to subspecies only where a given study makes particular reference to it.  (Back to Menu)

Kingdom: Animalia (Animals)
Phylum: Chordata (Possess a basic 'backbone')
Class: Mammalia (Mammals)
Order: Artiodactyla (‘Even-toed’ ungulates)
Family: Cervidae (Deer)
Subfamily: Cervinae (‘Old World’ deer)
Tribe: Cervini (‘True’ deer)
Genus: Cervus (Latin for “deer”)
Species: elaphus (from Greek elaphos, meaning “deer”)

For more information about how and why we classify organisms, please see the Taxonomy page.

Size: The following are generalised figures for the height, length and weight of Red deer.   As David Macdonald and Priscilla Barrett point out in their Field Guide to the Mammals of Britain and Europe, measurements of deer vary considerably according to habitat, population density and prevailing conditions.   The mammalogists also note that there is a distinct east-west cline, with animals in the east (e.g. in Scotland) being smaller than those in the west (e.g. North America), although if one subtracts the wapiti -- which aren’t the same species -- the difference is more subtle.   Indeed, in his Deer of the World, Valerius Geist considers the view that Red and wapiti deer form a gradual cline to be “unfounded”.   Overall, there is tremendous variation in size across their range, with deer living in poor habitat being stunted in both overall size and antler development.   At the lower end of the size range is probably the Corsican Red deer, which typically weigh in at 80 kg (176 lbs), while those of the Carpathian Mountains sit at the other end of the scale, attaining weights of six-times this.

Adult Red deer in the UK & Europe are usually between 1.6 and 2.6 m (5 ½ to  8 ½  ft) in length and a full-grown stag stands about 1.2 m (4ft) at the shoulder; hinds are slightly smaller, standing about 1 m at the shoulder.   Both sexes possess a tail of between 10 and 20 cm (4 – 8 in.) in length.   In the wild, adult Red stags generally weigh in at between 90 and 260 kg (200 – 570 lbs) depending upon the habitat, while hinds typically do not exceed 150 kg (330 lbs).   Weight at any given time is highly dependant upon season and food availability and a mature stag in very good conditions can weigh as much as 340 kg (750 lbs).   Individuals from England, especially English parks and deciduous woodland, are often significantly larger than conspecifics (other animals of the same species) on the impoverished hillsides and moorlands of Scotland.   The reason for this size disparity seems to be related to the amount of food available during the crucial winter months.   A study by a team of biologists at the Rowett Research Institute in Aberdeen, published in the British Journal of Nutrition during 1983, (further details in Food & Feeding) concluded:

“On Scottish hills deer reach a size appropriate to their environment rather than their genetic potential.”       (Back to Menu)

Colour: Red deer have a short, rich red-brown summer coat with little or no underwool, which starts to grow around May-time and is typically complete by late July or early August – the hair is a fairly consistent red-brown colour along its five centimetre-or-so (2 in.) length.   During September, a longer, coarser (hair is slightly corrugated) grey-brown winter coat starts to grow, and is complete by the end of the year.   The winter coat is accompanied by a layer of underwool about two centimetres (1 in.) thick; the hair colour changes from pale brown at the base to very dark brown or black in the middle and light red-brown at the tip.   The rump patch is a yellowish or cream colour (see left), with a short beige-coloured tail; rump patch colour varies tremendously in relation to geography and this is a feature commonly used as a distinguishing feature of subspecies.   Similarly, stags in some regions develop a mane during the autumn that’s carried for the winter months (e.g. in Britain); the mane is typically slightly darker in colour than the rest of the coat and may be accompanied by a dark stripe down the animal’s back.   The colour of the fur on the underside varies from off-white to yellowish or grey and on a rutting stag it may be heavily stained with urine and mud (giving a dark brown or black appearance).   The overall colour of the animal may vary according to location: Red deer residing between the Black and Caspian seas (the Caspian Red deer), for example, have a more uniformly-grey coat and lighter rump patch than those in Europe.

Newborn deer are spotted for the first few months of life, but spots are uncommon on adult coats, although on occasion adults have been observed with a double row of spots running down the back.   Calves undergo two moults in their first year: the neonatal “pomeled” (spotted) coat, which is shed at about two months old, is followed by the growth of the winter coat during the autumn.   Older stags and those in better condition generally begin and complete their moult before younger animals; the moult starts at the front of the body (i.e. head, legs etc) and progresses posteriorly.

Deviations from the ‘typical’ colouration seem rare, although as mentioned, some individuals may be darker or lighter than others.   Records of albino Red deer are rare; non-albino white ‘morphs’ are reported more frequently.   In his Whitehead Encyclopaedia of Deer, Kenneth Whitehead notes that white morphs of the Red deer have been preserved in deer parks, most notably Kinmonth in Perthshire, Charborough in Dorset, Woburn in Bedfordshire and Zleby in Czechoslovakia.   It seems that entirely or predominantly white individuals are occasionally reported from the wild, including sightings in the Scottish deer forests, Scotland’s Corrie Ba and on the Quantocks in Devon.   There are also various legends, superstitions and stories involving white deer, most notably stags, including that of David I of Scotland, who was apparently almost killed by a white stag in 1128, and the legend of a young white stag befriended by locals on the Island of Arran off Scotland’s west coast – unfortunately, the stag became too bold and was eventually shot by the estate’s Head Keeper in December 1970.

Colour variations may also take the form of “bald-faced” or white-faced individuals, which exhibit white patches on their heads, varying in size from a small patch on the forehead to a large white band down the length of the face between the eyes, or even a completely white face; individuals may also have white ‘socks’.   Additionally, in their contribution to Mammals of the British Isles: Handbook, 4^th Edition, Brian Staines, Jochen Langbein and Tim Burkitt mention that the summer coat is “sometimes whitish or skewbald [patches of white]”, an observation also made by Mr Whitehead.   Indeed, it seems that pure white morphs are uncommon and, in her 1991 book Deer, Norma Chapman notes that although white morphs of Cervus elaphus have been documented, they are seldom entirely white – they usually have a patch of red on them somewhere.   Interestingly, none of the aforementioned authors make mention of melanistic (very dark or black) forms.  (Back to Menu)

Distribution & Population: Red deer are found throughout much of Europe, including a large swathe covering north France, Germany, Austria, Czech Republic, Hungary, Slovak Republic and Poland.   They are also found in Norway, southern Sweden, parts of Latvia and Estonia, and throughout Turkey into northern Iran, north through Georgia into southern Russia and west to Crimea.   There are smaller populations in Spain, southwest France, west Italy and Yugoslavia.   Red are the only deer species that inhabit Africa, where they are found in the Atlas Mountains in the north of the continent.   This species is generally absent from Mediterranean islands, the exceptions being Corsica and Sardinia.   Outside of Eurasia, this species has been introduced to parts of South America as well as New Zealand and Australia.

In the UK, Red deer are most abundant in the Scottish Highlands and Outer Hebrides -- where they are still considered "native stock", generally referred to as Cervus elaphus scoticus -- although their distribution includes most of Scotland, with the exception of the eastern fringes of Aberdeenshire, Kincardineshire and Angus – they appear to be absent from Fife and a belt across southern Scotland from roughly north Ayrshire to Berwickshire.   Within England, there are isolated populations in the Lake District (Cumberland and Westmorland), parts of East Anglia (Cambridge, Norfolk and Suffolk), parts of Hampshire and Wiltshire (the New Forest), the Quantocks in Somerset, and Exmoor in Devon.   The 2007 Deer Distribution Survey (published by The British Deer Society) suggests this species has expanded into the Midlands (Yorkshire, Derbyshire and Lincolnshire) and further into East Anglia (Essex and Middlesex) and down into Surrey, Sussex and Kent in recent years.   There also appears to be expansion of the Hampshire population west into Dorset.

Red deer are apparently absent from many of our islands, including the Isle of Man, Orkney Isles and the Shetland Isles.   The Isle of Wight, just off the coast of Hampshire, is generally considered free of deer, except for those held in deer parks on the island (e.g. at Carisbrooke) – there are certainly no endemic populations.   However, there are some reports to suggest park escapees may have been living in the wild on some parts of the island.   In his round-up of the amphibians, reptiles and mammals recorded during site visits and surveys in 1997 (published in the 1998 Proceedings of the Isle of Wight Natural History and Archaeological Society), Richard Grogan mentioned escaped Red deer.   Apparently, a group of Red deer were frequently seen in the Calbourne/Brightstone Forest area in the south-west of the island, while three other individuals were seen wandering outside the deer fencing at Chale in the south during the same year.   In his round-up for 1999, Mr Grogan commented on deer grazing damage at Firestone Copse, near Wooton in the north-east, although he seemed to link this to Fallow deer (Dama dama), rather than Red.   The 2000 Proceedings were the last to include a round-up of vertebrate sightings, but Mr Grogan informs me that there are currently no known feral populations of Red deer on the island.

There are scattered populations in Wales, including Welshpool, Monmouthshire, and parts of the Lleyn peninsular – these probably represent escapees from Powis Castle near Welshpool and various deer farms.   There are isolated populations in Ireland, including Donegal, Down, south-west Connaught Province, Limerick, Wexford and Kerry.

Deer are typically secretive mammals that are acutely sensitive to humans (or predators) sneaking around in the undergrowth; even where they dwell in or close to large human settlements, they can be difficult to spot.   Moreover, deer often live in dense woodland/plantations or remote hillsides and the habitat in which they live contributes directly to the degree of ‘critical resource stress’ (i.e. some resource necessary to survival is in short supply) that the animal is exposed to, which regulates breeding success and ultimately controls population productivity.   Thus, it is not difficult to understand that they are hard to survey, making it a challenge to obtain accurate information about numbers and population demography (i.e. size, structure and overall changes in populations with time).   Over the years many have tried to estimate deer numbers in Britain, but only recently -- with the aid of large networks of scientists and volunteers using various techniques from counting scats to radio-tracking -- have we started to get what we think is a good idea of deer numbers.

In a 2005 paper to the journal Mammal Review, British Deer Society (BDS) biologist Alistair Ward presented an analysis of data collected by the BDS between 1969 (their first attempt to survey British deer populations) and 2002.   From the survey data, Dr Ward estimated that Red deer numbers had expanded at a compound rate of 0.3% per year, the lowest of the six species studied.   [Click here for an explanation of compound vs. simple interest]   The range expansion of Red deer in England and Scotland (recording efforts in Wales and Northern Ireland prior to 2000 were too low to provide a true picture of deer expansion) had also been much slower, and the total area into which they’d expanded was smaller, than for most of the other deer species.    Dr Ward suggested that, although Red deer use woodland throughout much of their range, the thick abundant new woodland plantings may offer less suitable habitat for them than other species (e.g. Roe deer, Capreolus capreolus), while the large urban gardens and parks that have assisted the spread of species such as the Roe and Muntjac (Muntiacus reevesi) are probably unsuitable for Red deer and may even represent a physical barrier that prevents or hampers their spread.   The data analysed by Dr Ward also revealed that Sika deer (Cervus nippon, left) had encroached significantly into the range of the Red, occupying 41 (7%) of the 10 km survey squares in the Red’s range in 1972 and 275 (36%) by 2002 – Dr Ward described this as a “trend that causes concern”.   Finally, by comparing the country-wide estimate of Red deer numbers provided by Steve Harris and colleagues in their 1995 JNCC publication A Review of British Mammals (360,000 animals) to the numbers estimated to be present in Mesolithic (12,000 to 3,000 B.C.) Britain, Dr Ward concluded that their numbers were “closer to their former population sizes than they have been for centuries”.

In their UK Mammals: Species Status and Population Trends report, published in 2005, the Mammal Tracking Partnership gave estimates of Red deer numbers in Scotland, England, and Wales of 347,000, 8,000 and less than 500, respectively; this puts the overall figure for British Red deer at 355,500, close to the estimate given by Prof Harris and colleagues in 1995.   The UK Mammals report also noted that the population in Scotland appears to have been increasing steadily since 1969 (although it may now have stabilised), while Red deer are increasing in both range and number across the south and west of England.

In the 2008 Mammals of the British Isles: Handbook, 4^th Edition, Brian Staines, Jochen Langbein and Tim Burkitt present a collation of the population literature and arrive at a figure of between 335,350 and 366,110 Red deer in the major populations within the British Isles.   A breakdown of their data suggests that the vast majority of these deer (some 95%) live on the hillsides and plantations of Scotland.   These figures tally with the Parliamentary Office of Science and Technology’s POSTnote, published in February 2009, which gives a population estimate for Red deer of “>350,000”.   The POSTnote gives the same estimate of population growth as Dr Ward’s 2005 appraisal: roughly 0.3% per annum.

Unfortunately, the situation in Ireland is less clear.   There were insufficient survey data for the UK Mammals report to estimate deer numbers here and neither the POSTnote nor Dr Staines and his co-authors make any specific reference to Irish numbers.   The Wild Deer Association of Ireland (WDAI) doesn’t offer an overall estimate of numbers although, on their website, they do note that there were 690 Red deer in the Killarney National Park during the mid-1990s.   More recently, in February of this year (2009), several newspapers carried the story that Ireland’s authorities (in this case the Irish Farmers’ Association, Irish Deer Society and WADI in conjunction with the government) were planning a widespread cull of deer.   The quotations carried by the newsmedia didn’t provide details as to the number of different species, but they did suggest that upper estimates put the total number of deer in Ireland at around 100,000.   Despite this, on their website, the Irish Deer Society point out that: “It is not known how many [deer] there are in Ireland as no national comprehensive survey has been done.”

It should be noted that a drawback to using national estimates of population figures is that they can mask local trends.   In the New Forest, for example, numbers have fluctuated considerably even to the point of this species disappearing from the Forest altogether.   The New Forest Park Authority currently estimates there to be about 180 Red deer on the Crown Lands, a number that is actively maintained by stalkers.   Elsewhere, Red deer populations have apparently seen a considerable increase locally in recent years.   In his 1972 book on the subject, Eric Lloyd estimated that there were 500 to 800 Red deer on Exmoor, a figure that was increased to between 700 and 900 by Gordon Miller, John Miles and Bill Heal in their 1984 A Study of Exmoor, and upped again by Noel Allen in his 1990 book Exmoor’s Wild Red Deer, who put the figure at around 1500.   Today, the Exmoor National Park Authority estimates that there are some 3000 Red deer on the farms, woodland and moorland of Exmoor.   Similarly, a report published by the Royal Society for the Protection of Birds and what was the World Wildlife Fund (now World Wide Fund for Nature) in 2003 suggested that, after massive declines in numbers up to the 1800s, deer populations in the Scottish Highlands have now exploded; the report cites an increase from 300,000 in 1989 to 450,000 in 2002.   However, in a brief communication to the journal Nature during 2004, Tim Clutton-Brock, Tim Coulson and Jos Milner argue that the Scottish deer population is unlikely to be increasing by such a startling rate, pointing out:

“A large part of the apparent increase [given in the RSPB/WWF report] is due to the arbitrary tripling of the estimated number of deer living in woodland, where they cannot be counted reliably.”

Deer density is another feature that can vary considerably locally and, as we shall see shortly, the distribution of resources has a pivotal influence on the area over which an animal needs to range in order to find sufficient food.   Consequently, the number of deer that live in an area is dependant upon the resources therein and this is significant in explaining the considerable variations we see in deer densities.   The Mammals of the British Isles: Handbook, 4^th Edition provides estimates of 10 to 15 animals per sq-km in major deer forests and plantations, 20 to 25 per sq-km in Ireland’s conifer woods, nine per sq-km on open hillsides and in excess of one hundred per sq-km on some winter ranges.   In their 1993 Field Guide to Mammals of Britain and Europe, David Macdonald and Priscilla Barrett give population densities of between five and 45 animals per square kilometre, depending on the habitat.

A summary of the fluctuation in Red deer numbers in Britain as a result of human interference and management can be found in the Interactions with Humans section.  (Back to Menu)

Ageing & Longevity: There are various myths involving long-lived stags.  Perhaps the most famous is a Gaelic proverb that, according to John Fletcher in his A Life for Deer, can be traced back to the Greek poet Hesiod and forms the basis for the mediaeval pavement in front of the high alter at Westminster:

Thrice the age of a dog, the age of a horse;
Thrice the age of a horse, the age of a man;
Thrice the age of a man, the age of a deer;
Thrice the age of a deer, the age of an eagle;
Thrice the age of an eagle, the age of an oak tree.

Assuming a generous estimate for ‘old age’ during the Iron Age, this would put ‘the age of a deer’ at about 120 years old!   Equally, even if the proverb was written by Hesiod, who many scholars believe lived during the eighth century BC, we still arrive at an impressive age of 90 years for the deer.   As one might expect, modern day estimates don’t come anywhere close to these values.

According to Frankfurt Zoo biologist Richard Weigl’s Longevity of mammals in captivity; from the Living Collections of the world, the oldest Red deer on record is a female (listed as subspecies sibiricus) who was born at Kiev Zoo in July 1968 and died in January 2000 at the ripe old age of 31 years and six months.   Mr Weigl published longevity records for 20 subspecies of Cervus elaphus in his 2005 book – the record for the subspecies elaphus stands at 21 years and 4 months, while that for scoticus is held by a female born at Washington Park Zoo during October 1927 that died in June 1954 at the age of 26 years and eight months.   Interestingly, Mr Weigl doesn’t mention a hind, nicknamed ‘the old lady of Richmond Park’, who apparently survived to 27 years old.

Despite these rather impressive figures, these are all ages for captive deer and the maximum age that an animal can reach in captivity (with plenty of food, no predators, veterinary care etc.) is often a far cry from the maximum age attainable in the wild.   A cursory inspection of the literature suggests that the oldest wild hinds attain about 25 years old, while stags reach about 18 years old.   Arguably, reaching 25 in the wild is the exception rather than the rule; indeed, records of wild hinds living beyond 15 years and stags beyond 12 years are rare.   Overall, the demographic data from the population of Red deer on the Scottish island of Rum suggest that few specimens live longer than about eight years.   In her 1991 book, Deer, Norma Chapman pointed out that some researchers have estimated that 50% of Scottish Red deer attain an average age of four years, while only 25% reach eight-years-old.   Interestingly though, in volume three of his Mammals of Great Britain and Ireland (published in 1906), English naturalist and travel writer John Guille Millais wrote that Red stags reach their prime at about 11 years old and remain at this ‘peak’ for another four or five years!

Ageing Red deer from their physical appearance is not an easy task.   There are many features that experienced stalkers may use to assess age -- for example body size, head length, time of moult, antler casting, and various aspects of antler morphology – but, as Rory Putman pointed out in his 2005 report for the Deer Commission for Scotland:

“None of these factors however shows linear correlation with age.  Thus indicators used may be sufficient simply for categorical distinction between discrete age classes rather than as indicators of precise age.”

Indeed, most books on deer make reference, at some point, to it being a common misconception that you can age a deer by counting the points on its antlers – while the general pattern of antler development seems to be ‘genetically fixed’ there are other factors (most notably food quality) that can influence the final arrangement.   Nonetheless, this doesn’t mean that we shouldn’t look at antlers in a bid to estimate age.   Indeed, in their contribution to Mammals of the British Isles, Brian Staines, Jochen Langbein and Tim Burkitt note that, while antler size per se is a poor indicator of age, beam width, coronet breadth and height of the coronet above the skull are good indicators.

Obviously, antler morphology is only of any benefit during certain seasons, and if the animal you’re trying to age is a male, even then there can still be some ambiguity associated with antler measurements.   Consequently, biologists turned their attention to teeth.   When using dentition to infer age we are immediately confronted with the problem that, contrary to popular misconception, it is difficult to reliably tell the age of an animal from tooth wear, and tooth eruption is of limited use.   Tooth eruption is generally only helpful for young animals (up to the age they obtain their permanent dentition).   Indeed, in a 2002 paper to the journal Anales de Biologia, a group of Spanish biologists report their findings from a detailed study of the tooth eruption pattern in Red deer from Sierra Morena in southern Spain.   The researchers concluded that, despite some difficulties (including delays in the replacement and eruption of some teeth), it is possible to determine age in this species up to three-and-a-half years old by studying gradual changes in the teeth.   In a 2003 paper, three of the same Spanish researchers found that whether or not the mandible (lower jaw bone) is fully grown may also point to the deer’s age, with female mandibles being fully developed at around 55 months (4.5 years) and males complete at about 80 months (6.5 years), although this requires the deer to be dead in order to confirm.   A similar study in Norway yielded similar results; in a huge sample of more than 40,000 Red deer it was found that there was a distinct relationship between mandibular proportions and age, but this decreased with age and the relationship between mandible size and weight was almost flat by the age of five years.

In her 1991 book, Deer, Norma Chapman noted that studies of captive Red and Fallow deer found that it was possible to age the animals based on the level of wear on and between each slope of each molar, with the total score giving the deer’s age.   Indeed, based on his studies of the Red deer population of Rum, Victor Lowe wrote in a 1967 paper to the Journal of Zoology that “88% of the marked deer up to the age of 8 years could be reliably aged from tooth replacement, eruption and wear”.   Despite Dr Lowe’s success, the amount of wear on teeth is typically a poor indicator of age, because the rate at which teeth wear down is almost exclusively a result of the animal’s diet – there are some other contributing factors (tooth topography and genetically controlled tooth mineralisation, for example) but it generally holds that the coarser the diet, the quicker the teeth wear.   Thus, two populations of the same species could easily display different degrees of tooth wear if they’re feeding on a different diet.   Moreover, work by Leif Loe at the University Center in Svalbard in Norway, between 1971 and 2001, suggests that tooth wear actually decreases with age in Red deer.   In a 2003 paper to the journal Oecologia, Dr Loe and his colleagues present data on tooth wear for 2,659 Red deer (roughly evenly split between the sexes) between three and 25 years old.   The zoologists found that the rate of tooth wear declined with age such that four year old stags wore down their molars at about 0.61 mm per year (0.024 in.), while stags at 11 years old displayed wear rates of only 0.45 mm per year (0.018 in.).   Rates of wear were slightly lower in females, with four and 11 year old hinds experiencing 0.52 mm (0.020 in.) and 0.39 mm (0.015), respectively.   The authors suggest that this difference in rate of wear between the sexes is a result of a difference in diet selection, with males feeding on a lower quality diet than females.   Indeed, it has now been well established that many grasses have granular structures called phytoliths, of various sizes and shapes, made of silica on the surface of their leaves – these phytoliths are hard and sharp (this is why you can cut yourself on grass) and cause considerable wear on the teeth of herbivores.

Given the problems associated with inferring age from tooth eruption or wear, during the 1960s, scientists came up with the idea of looking inside the teeth.   More specifically, they discovered that you could get a pretty good idea of a deer’s age if you sectioned a tooth and counted the annuli (‘rings’) in its root – this is known as the cementum method of ageing.   The biochemistry that governs the deposition of annuli is rather complex, but essentially it appears that deer are low in blood-serum protein and phosphate during the winter months, which leads to improper calcification of the tooth’s cementum.   This poorly calcified, narrow layer (sometimes referred to as a ‘rest line’) shows up as a darker band in the tooth and there should be one such band present for each winter through which the deer has lived.   In a 2004 paper to the Wildlife Society Bulletin, the same Spanish biologists -- who published their data on Spanish Red deer tooth eruption and mandible growth -- report on the efficiency of ageing deer by using growth marks in their teeth.   The researchers found that molars provided the most accurate ages, correctly ageing 75% of their animals, while only 49% of age estimates made from incisors were correct.   However, when the scientists widened the goal posts a little, increasing the confidence limit to one year (i.e. the estimate could be either a year over or under the actual age), they found that molars and incisors could be used to accurately age 99% and 86% of the animals, respectively.   Interestingly, the researchers found that the first ‘rest line’ was deposited in the molar at six months old, while it didn’t appear in the incisor until the animal was 15 months old, so additional caution may be necessary when interpreting ring data from incisors.

Studies on White-tailed (Odocoileus virginianus) and Mule deer (O. hemionus) by American biologists have suggested that it is possible to age deer fawns based on the wear on their hooves.  However, while this method seems fairly reliable on captive fawns, much like tooth wear, it is tempting to think that there are a considerable number of factors that can influence this characteristic and this may cause confusion when applied to wild animals.

Before we leave the subject of age in deer, let us briefly touch upon the fascinating phenomenon of ageing rate, described as “dramatic and sudden” in an article on the BBC News website during August 2009.   In a paper to the journal The American Naturalist, a team of biologists led by Edinburgh University’s Dan Nussey reported 40 years’ worth of data on senescence (i.e. the signs of getting old) in Red deer from the Isle of Rum.   The biologists uncovered a complex pattern in which the signs of old age appear at different times, with significant differences between stags and hinds.   Dr Nussey and his team found that, although stags seemed perfectly capable of growing and maintaining antlers into their twilight years, those more than about 10 years old rapidly became less successful at rutting and typically fathered fewer calves – there are, of course, exceptions here and fans of the BBC’s AutumnWatch will probably recall that a Red stag named Percy won their ‘2009 rut award’ after being seen to mate with more hinds than any other stag, despite being 14 years old.   Similarly interesting data were presented for females, which seem to start showing signs of old age at around nine years old.   It appears that, despite starting to ‘look older’, hinds were able to successfully calf well into their teens and even females that were considered ‘past their prime’ were observed to continue breeding, although their offspring were typically smaller and thus less likely to survive their first winter than those of younger hinds.

In addition to markedly different patterns of ageing between the sexes, Red deer also appear to have a rate of senescence that is heavily influenced by their early life conditions, especially the number of other deer around.    In a fascinating paper to the journal Current Biology during 2007, biologists from Edinburgh and Cambridge Universities, again led by Dan Nussey reported that:

“… females experiencing high levels of resource competition during early life showed faster rates of senescence as adults.”

Basically, more deer means greater competition for resources and Red deer hinds effectively age more rapidly when food is scarce.   Additionally, the researchers found that the likelihood of a female producing a calf declined more quickly with old age in hinds that experienced harsh conditions early in life.   Hinds that were born later as a result of their mother being exposed to harsh conditions were found to start breeding later than those born to hinds breeding during favourable conditions.

Overall, while there are methods by which we can establish the age of a Red deer, it is always worth bearing in mind that the phenomenon of ageing and senescence is complex and, in hinds at least, appears very closely tied not only to the conditions in which she lives, but also those experienced by her mother early in life.  (Back to Menu)

Sexing: In most cases, males are easily separated from females during the breeding (rutting) season by the presence of antlers and, typically, a mane of longer hair.   During the spring, young males can often be separated from females by the presence of developing antlers – these develop from bony structures, called pedicles, which constitute part of the skull.   Some authors point to it being possible to sex newborn calves and even foetuses based on the swellings that will eventually form the pedicles.   Indeed, in 1973 deer biologist Gerald Lincoln described how he was able to sex foetuses as young as 60 days old (some six months before birth!) by looking at head swellings associated with antler development.    There are some (rare) instances where males fail to develop antlers altogether, usually because they fail to develop normal pedicles – these animals are referred to as “hummels” or “notts” and all other sexual development seems normal.

Closer inspection of the animal may reveal the penis sheath -- the external genitalia is evident in foetal deer by just under two months old -- and, especially during the rut, the stag’s underside will often be stained with urine.   Males are typically larger and heavier than females and differences may be noticeable in the shape of the head.   In a 2003 paper to the journal Acta Theriologica, three Spanish biologists demonstrated some sexual differentiation in the mandible (lower jaw) of Red deer from Spain.   The biologists studied 126 mandibles and found that female mandibles are fully grown more than a year before those of males.   The researchers also found that several of the measurements they took -- including the angle of the jaw and size of some sections at the back of the jaw -- were consistently larger in males than females.   However, the biologists also observed significant variation associated with climatic factors, which may lead to some ambiguity in assigning sex.   In his book Kia: A study of Red deer, Ian Alcock noted that Red deer have very elongated faces and that youngsters have quite short faces that elongate as they get older such that adult hinds have very long noses.

Outside of simply studying a deer’s appearance, it may sometimes be possible to sex them by proxy, using their droppings.   One study, published in 1994, demonstrated that it was possible to sex Fallow deer on the basis of their scat pellets, although no similar data were included for Red deer.   In 2008, however, a group of Chinese biologists were able to correctly assign the sex of 108 (59%) of the 183 faecal samples collected from Red deer by subjecting them to genetic analysis.   Finally, a study published during 2005 by a team of American biologists, led by Douglas Tolleson at the Texas A&M University, demonstrated that it was possible to identify both sex and species of deer by bouncing infrared light off their scat pellets in a process known as Near Infrared Reflective Spectroscopy (or NIRS, for short).   However, the team had mixed success with their samples, being able to identify Fallow more consistently than Red and females with greater accuracy than males.

The sexes generally spend most of the year apart (see Behaviour & Social Structure), coming together in the Autumn to mate (see Breeding Biology).   Males are called stags, females are hinds and the young are calves.  (Back to Menu)

Activity: Red deer are active over the full 24 hour period, but exhibit both crepuscular and seasonal peaks in activity, with their longest periods of activity at dawn and dusk (the term crepuscular is derived from the Latin crepusculum, meaning “twilight”).   Studies of radio-collared deer in the Slovak Republic (Central Europe) have found that these animals spend anywhere between 20% and 90% of their time feeding, according to season, then reducing their activity during the late winter months (January and February).   The same study also found that there was about a 60% decrease in heart rate during winter (compared with summer peaks) and documented a previously unknown case of nocturnal hypometabolism (i.e. where the deer reduce their metabolic rate at night to cut their energy expenditure during winter) in this species – the deer achieve this by lowering the temperature of peripheral body tissues by 10^oC (50^oF) or more over the daytime highs, which reduces heat loss.   It seems that the majority of the variations found in the deer’s metabolic rate over the year could be linked to the heat increment of the vegetation available to the deer as food.   When an animal eats something, it generates heat in the process of digesting it and it is this increase in heat production following the consumption of food that biologists call the heat increment.   The authors of this study, which was published in the American Journal of Physiology during 2004, wrote:

“…the approximately twofold difference between the annual maximum and minimum of daily mean heart rate corresponded well with the also twofold higher protein content of natural deer forage at the summer peak compared with the winter low.”

Indeed, with the exception of the stags during the rut, the bulk of a deer’s time is spent trying to find enough food and, as such, their activity patterns are intrinsically linked to the food available to them.   When the rumen is full the deer cannot eat anything else and they must stop feeding and start ruminating.   Red deer exhibit a feed-ruminate cycle of between five and nine hours, depending on the type of food taken; this results in a clear pattern of activity, cycling through periods of feeding and periods of ruminating.

Red deer living in open hill areas (e.g. Scottish Highlands) tend to exhibit a pronounced activity cycle: they spend much of the day at high elevations resting and ruminating (in some seasons elevation may help reduce irritation from biting flies – see below), descending at dusk to feed during the night, before returning up the hillside at dawn.   Deer inhabiting woodland have a similarly pronounced cycle, whereby they spend the daytime in, or close to, tree cover where they rest and ruminate (there may also be some browsing) before moving into more open areas (e.g. meadows, clearings and agricultural fields) at dusk to feed.   Studies of Red deer in Scandinavia and New Zealand have found that they are more nocturnal in areas of high human disturbance.   Deer of both sexes can also be seen wallowing in mud holes during the daytime; this is especially true of stags during the rutting season.   The activity level of males increases considerably during the autumn rut and stags will typically rest, eat and sleep little (if at all) during this period.   Indeed, time budget studies suggest that feeding may account for less than 10% of a stag’s activity during the rut.

Overall, the level of activity during the rutting season, which runs from the end of September to the end of October, will depend upon prevailing weather conditions (inclement weather can reduce activity considerably) as well as population density and levels of disturbance.   Stags on the island of Rum, for example, represent a high-density population that is subject to little human disturbance (culling is prohibited on some areas of the island) and as such the competition for mates is high and rutting stags will not generally eat or sleep all the time there are hinds to be coveted.   In more disturbed places, such as the New Forest in Hampshire, where culling pressure and human disturbance results in small populations of deer, there may be few suitable challengers and the rutting stands can be monopolised by a single large stag – the lack of competition means that it is not uncommon to see the stag resting and feeding with the hinds, breaking off only to chase away interlopers.   In situations where competition with other stags is low, rutting males tend to bellow less than conspecifics in locations where competition is high.

Contrary to popular misconception, deer do sleep, although not in the same manner that we humans do.   The electrical chemistry of the brain during rumination is similar to that of (mammalian) sleep, meaning that they can stay ‘awake’ chewing the cud, with their eyes glazed.   However, there are times when ‘genuine’ sleep is necessary and, according to Pennsylvania wildlife biologist Kip Adams, a typical bout of sleeping includes:

“… 30 seconds to a few minutes of dozing, followed by a brief alert period, and then more dozing followed by an alert period. This cycle often lasts for about 30 minutes. Generally, once per 30 minutes deer will stand and stretch and they may urinate or defecate before laying back down.”

During periods of rest, which may account for 50% to 60% of their time during winter and 40% to 60% during summer months, the deer remain bedded down at sites for which they may have considerable fidelity.   Between June 1999 and December 2000, a team of French biologists monitored the activity patterns of seven wild adult Red deer -- in the Le Parc National des Cévennes (southern France) -- that had been caught and fitted with GPS radio collars.   The researchers found an interesting duality in bed site choice by the deer: the animals appeared to be facing a choice between availability of feeding sites and sufficient cover.   During the daytime, the deer opted for sites with greater cover, while at night (when the deer were less affected by disturbance) the deer could be less selective and chose resting sites with more variable characteristics.   The study, which was published in the European Journal of Wildlife Research during 2008, also found that the deer resting bouts were shorter during the night than during the day from June to October – both sexes reduced their resting activity during the rutting season.   There was no significant difference between the resting bout lengths of stags and hinds, although hinds tended to use steeper slopes than stags, presumably because these were less disturbed than more open habitats.

Disturbance seems the key factor in explaining deer bedding site choice, because work on the undisturbed populations of Rum by Cambridge University and Edinburgh University biologists demonstrates no occurrence of such variations in day and night time rest site.   Moreover, recent work by researchers at the Northeast Forest University in China has found that Red deer in the Wandashan Mountains of northeastern China avoided human-altered habitats (e.g. villages and forest roads) for movement, bedding and foraging because of disturbances during late winter – bedding sites were sensitive to disturbances from humans and other ungulates.   The scientists also observed that the deer chose ridges and slopes with a south-eastern and southern exposure as bedding sites during the winter; these were presumably selected because of their warmth and might thus offer energy savings to the deer.

It is also worth mentioning that deer lying down may not be either sleeping or ruminating; they may be trying to avoid biting flies.   In an interesting paper to the journal Behavioral Ecology and Sociobiology back in 1979, Yngve Espmark at the University of Trondheim and Rolf Langvatn of the Norwegian State Game Research Institute reported that resting times of captive Red deer at the Songli Research Station, central Norway, were more than twice as long on days when fly harassment was severe.   Earlier work by English ecologist Fraser Darling during the 1930s had established that tabanid flies (horse flies) can have a profound impact on the activity patterns of Red deer, with outbreaks causing, among other things, changes to the spatial organization of the social groups; Espmark and Langvatn found that Hydrotaea irritans (see right), the so-called ‘head flies’, can also take their toll.   The biologists observed that on days when fly harassment was estimated as nil, the deer spent 33% of their time lying down; this increased to 71% on days of severe fly harassment.   It seems that, when the deer laid down, the number of flies hanging around dropped, probably (the biologists argue) because a resting animal is less attractive than a moving one, perhaps because it has a lower body temperature, is breathing out less carbon dioxide, perspiring less, and so forth.   Logically, lying down may also reduce the surface area of the body available for flies to bite.

Recent tracking data have suggested that, over some parts of their range at least, Red deer movements are highly seasonal.   In a paper to the Eurasian Journal of Wildlife Research last year (2009), Dominique Pepin and two colleagues -- all at France’s Institut National de la Recherche Agronomique -- presented the data from their monitoring of Red deer fitted with radio collars in the Cevennes National Park in central France.   Unfortunately, the biologists were only able to trap four Red deer (two stags and two hinds) so it is difficult to draw many conclusions from their study, but the GPS data do, nonetheless, make interesting reading.   Overall, the hinds moved greater distances than the stags (although the stags tended to move further during the night); it seems that there is only a short period during the year when female walking activity is drastically reduced and this is during the rut, when they are found on the rutting stands.   The females were most mobile between the hours of 15:00 and 18:00 and least active during the night (between 21:00 and 03:00).   The stags exhibited peaks of increased walking at 06:00 and 18:00.

Dr Pepin and her colleagues noted that males moved around least between November and January, having been most active during the rut; the authors suggest that the change in the weather, with average minimum temperatures of 0^oC at the study site may be the cause as the deer moved around less to conserve energy.   Males have lower body fat reserves during this time of the year, having been engaged in the rut during much of September and October and so may be more sensitive to changes in weather (and specifically temperature) than females.   This seems apparent in the dataset, which show females active throughout the winter until the end of February, when walking activity declined.   Overall, the authors concluded:

“The walking activity of males peaked during the rut whereas that of females decreased.  But compared to males, females moved more both during winter and daylight hours.”       (Back to Menu)

Habitat: Red deer are predominantly a species of open deciduous and mixed woodland although they are highly adaptable animals and can be found in conifer plantations, open grasslands and meadows, river valleys and flood plains, parkland, scrub and on moorland.   They are rare in large areas of very dense forest and aren’t typically associated with visits to gardens, as Muntjac and Roe can be.   This species is generally found below the treeline, although where they persist at higher altitudes (e.g. the Alps) they may be found feeding above the treeline during the summer.   In Britain Red deer are found in their greatest numbers on open moorland; they are also found in ancient and plantation woodland, especially where such areas are peripheral to agricultural land used for growing crops.   During the summer months in Scotland the deer are generally to be found on high ground with new heather growth during the day; typically, they will move to lower ground during the winter months.   The Red deer sexes live apart during most of the year, with hinds monopolizing more productive grassy areas, and stags confined to nutrient-poorer heather regions.

On Scotland’s Isle of Rum, Red deer make use of the seaweed habitats during the winter months.   Zoologist Larissa Conradt, currently at the University of Sussex in Brighton, studied the use of this habitat by deer during her time with Cambridge University’s Large Animal Research Group.   In 2000, Dr Conradt published a paper in the Journal of Zoology documenting her findings.   It seems that, although seaweed comprises less than one percent of the total habitat area of Rum, it forms an important part of the deers’ diet, with stags and hinds spending on average 18% and 12% of their time, respectively, foraging there.   The stags and hinds remained segregated while feeding; the two sexes generally used different bays and, where they used the same bay, they used different fractions of the seaweed (males preferred washed up seaweed, while hinds actively grazed on growing algae).   Analysis of the rumen contents of an adult hind revealed that just over 17% was seaweed, with Laminaria kelp (the Phaeophyceae, or brown algae) being the most common – this is perhaps not surprising, given that it is also the most nutritionally-rich species of algae growing in the bays.   Dr Conradt noted that some of the deer seemed especially keen on the seaweed and were seen to watch the coast long before low tide and make a bee-line for the beach as soon as the tide had gone out sufficiently far to permit grazing.   Perhaps most interesting was the finding that the use of seaweed habitat was closely correlated with whether their mothers used the habitat, which implies that some deer may learn to include seaweed in their diet.

Red deer have adapted to a wide range of different environments, but strong preferences for certain types of habitat are apparent in some parts of their range.   Additionally, habitat use may be heavily influenced by weather, with stags seeking shelter more readily than hinds, even if this means occupying sites with lower quality resources.   Indeed, the observation that males seem more sensitive to the prevailing weather than females has been put forward to explain the sexual segregation found in this species – it is known as the ‘weather sensitivity hypothesis’ and is discussed in the Behaviour and Sociality section.  

Observational data collected by mammalogists at the Polish Academy of Sciences on managed plots in the Bialowieza Primeval Forest during 2008 suggest that Red deer show a preference for feeding in forest gaps.   The study, published in the journal Forest Ecology and Management earlier this year (2009), found the visitation frequency of all the ungulates combined (i.e. European bison, Red deer, Roe deer, moose and wild boar) was almost twice as high to forest gaps as to areas of closed forest; Red deer showed the strongest preference of any species, with single visits to gaps lasting almost seven times longer than visits to sites in the closed forest.   It seems that the deer were attracted to the gaps because of the relative abundance of regenerating trees and the broader array of tree species found there.   Biologically-speaking, the process is fairly straightforward – when gaps are created in a previously closed canopy, the increased light level leads to an increase in the growth of the trees, while also allowing the growth of some that may have been shaded out by the established trees.   This abundance of new growth attracts plant predators.  (Back to Menu)

Territory & Home Range: In the strictest sense of the term, Red deer stag territoriality is seasonally ephemeral – that is to say that they establish a territory for a brief period during the breeding season.   The territory is small, generally consisting of a small area to which females (most of whom will be coming into oestrus) come to feed, and can be mobile – if the hinds move, the stag goes with them (although there is a degree of ‘rounding-up’ while the hinds are using the stand).   There is a common misconception that the rut is about stags ‘gathering up’ as many females as possible during the rut and holding them in their territory until they’re in season and can be mated.   In fact, it is the hinds that very much call the shots.   The hinds are drawn to rich feeding grounds as autumn draws in and it is the males that congregate at this prime real estate to try and keep control of a section of it.   If done well, this area will be that most favoured by the hinds and the stag will succeed in holding a sizeable group.   Thus, the territory of a dominant rutting stag can move in accordance with the movements of the hinds – it is the hinds that the stag is defending, rather than the ground on which they feed.

The stag that succeeds in defending the females against interlopers has the opportunity to mate with them as they become receptive and, although he may permit other stags into the area, any attempt by them to approach the hinds is met with a challenge.   The group of hinds in this situation is referred to as a ‘harem’ and this form of breeding strategy is called harem defence.   In areas where resources are scarce and female distribution is both patchy and predictable, stags may shift from harem defence to more ‘inclusive’ territoriality, where they defend an area (that may cover several hectares) from other stags.   Territoriality in this sense has only been demonstrated for Red stags in parts of Spain, although Dr Juan Carranza and his team at the Universidad de Extremadura have shown, through the provision of supplemental food, that:

“territoriality should arise in other red deer populations if resources are scarce and patchily distributed during the rut so that the use of space by females produces places that are worth defending.”

The experimentally-induced territoriality documented by Dr Carranza and his colleagues shows that stags are able to make quick decisions about which strategy to employ, based on a few days assessing the prevailing conditions.

Outside of the rutting season there is no evidence for territoriality in either sex, although tracking studies suggest that hinds show a greater site fidelity than stags, which tend to disperse further and be more nomadic.   Overall, the area over which any animal will roam is directly dependent upon the availability of key resources – one such crucial resource is food.   The more food around, the less you have to walk to find it and the smaller the area you need to cover to stay fed.   Similarly, the better the quality of the food (in terms of high nutrient content), the less of it you typically need to consume to get your recommended daily allowances.   Consequently, the overall home range of a deer varies not only according to the habitat in which they’re living, but also with the nutritional requirements of the animals; this can lead to variations in range size according to sex.   Hinds have high energetic demands during the winter because they’re carrying a developing foetus, and thus monopolise the high quality grazing, forcing stags to feed in relatively poorer areas.   Consequently, the stags need to cover more ground to get sufficient food and need larger ranges than hinds.   There is considerable geographic variation, but in the Scottish Highlands a stag may range over 800 ha (~ 2,000 acres) or more, while a hind requires roughly half of that.   In their contribution to Mammals of the British Isles: Handbook, 4^th Edition, Brian Staines, Jochen Langbein and Tim Burkitt give ranges of 200 to 400 ha (500 – 1000 acres) for hinds on Rum and 900 to 2400 ha (2200 – 6000 acres) for those in the East Highlands of Scotland.   Tracking studies by University of Exeter biologist Jochen Langbein found that hinds on Exmoor had home ranges between 275 and 711 ha, with the average being 430 ha (1062 acres); each deer’s range contained a single, smaller core area in which they spent the majority of their time.   The stags on Exmoor, conversely, ranged over about 1100 ha (2700 acres) and their activity was concentrated in two core areas that were occupied on a seasonal basis.

In most habitats there is a pronounced seasonal difference in the range of Red deer; winter is generally spent on low ground and summer at higher altitudes, with males typically found lower than females during the winter and higher during the summer.   Possible reasons for such sexual segregation are discussed in more detail in the Behaviour and Sociality section below, but it is interesting to note that such seasonal range use is not always apparent.   Tracking studies by Brian Stains in Scotland and Jochen Langbein on Exmoor have demonstrated that hinds in Scottish plantations and on Exmoor don’t appear to have any seasonal differences in their range, while the stags in the same areas do.  (Back to Menu)

Survival, Mortality, Parasites & Predators: As Dr McDiarmid points out in his review on the subject of deer mortality for Mammal Review in 1974, all deer must die sooner or later and death is an important facet of their ecology.   Overall, it is estimated that about 3% of the adult Red deer population currently die each year from ‘natural causes’, although this is dependent upon habitat and age.   Indeed, Red deer exhibit two ‘critical periods’ for mortality – early and late in life.   Studies on the Red deer of Rum by the Red Deer Research Group (RDRG – a collaboration between Cambridge and Edinburgh Universities) have provided a comprehensive picture of survival rates for this wild population.   In a paper to the Journal of Animal Ecology published during 1969, Victor Lowe constructed life tables (showing the mortality rates of each age group of a population at a given time) of the deer on Rum in a bid to get a general picture of the population structure.   Dr Lowe found a gentle reduction in survivorship up to around eight years old (around 1% per year for 2 – 7 year olds), after which there were two years of very heavy mortality (i.e. most of the adult deer dying in the population were in their ninth or tenth year) and then a return back to lower, but increasing, level.   From his reconstruction of the 1957 population, Dr Lowe estimated that only 8.4% of the population were older than eight years. 

In a subsequent paper to the Journal of Animal Ecology (during 1978), Fiona Guinness, Tim Clutton-Brock and Steve Albon presented data on calf survival between 1971 and 1976 on the North Block of Rum.   The biologists found that, on average, 18% of calves died before they reached five months old (i.e. by September of their first year), most (78%) within their first week, and a further 11% failed to survive the following winter, most dying during March.   Overall, the researchers found that anywhere between 19% and 35% (the average being 28%) of calves died before their first birthday, which compares favourably to Dr Lowe’s data, which record 37% of calves dead before they reached a year old.   It should be mentioned, incidentally, that mortality can be much higher, and more recent data suggest that as many as 65% of calves may fail to survive their first winter if conditions are particularly bad.

The level of mortality seen in any given year is the product of a complicated interrelationship between, amongst other influences, weather, population density, birth weight and time of birth.   Dr Guinness and her team found that light-born calves were less likely to survive their first winter than heavier ones, although light-born hinds were more likely to die than light born stags, while heavy-born stags were less likely to survive than heavy-born hinds.   Additionally, calves born late in the year were more likely to die than those born earlier in the year or during the main birthing period because they have less time to increase their body weight in time for winter.  The 1971-76 dataset also revealed that calves born to young or old hinds were more likely to die during their first six months than those born to hinds between seven and 10 years old – it appears that old and young hinds produced smaller than average calves.   Indeed, the age and thus experience level of the mother can be a crucial factor in calf survival.   Dr Guinness and her colleagues found that 10 (32%) of the 31 calves, for which cause of death could be firmly established, died because they were deserted or killed by their mothers.

Work by the RDRG (the 1971-76 data set and subsequent studies) has also shown that deer survival is closely related to both population density and weather conditions.   On parts of the island where population densities were high during the 1979 study, so too was calf mortality; increases in winter (although not summer) mortality were associated with increases in population density.   This is to be expected because as a population grows, so too does competition for food.   Indeed, a study published in the journal Ecology during 1997 presented population data for Red deer on Rum between 1984 and 1993 and concluded that local population density was more important in determining calf survival than total population density.   The authors, lead by Zoological Society of London biologist Tim Coulson, wrote:

“We propose that high local density of deer occurs on herb-rich Agrostis-Festuca grassland.  Calves born here are more likely to die due to high levels of competition for food than in other areas of poorer grazing and low local density.”

In other words, the deer flock to the areas where bentgrass and fescue grasses grow because they’re a good quality food.   Consequently, each blade of this grass has more hungry mouths going for it here than in areas of lower quality grazing, which means that the youngsters have more competition for food.   According to the study, the main factor influencing whether or not an individual survived the winter was its condition at the end of summer – the calves must gain weight and grow rapidly during the summer months if they’re to survive winter.   The authors go on to mention that males are more likely to die than females, because they grow faster and therefore require more food, making them potentially more susceptible to competition.   Indeed, another of the RDRG’s findings has been that stags seem more sensitive to environmental conditions than hinds.   Stags born on Rum during cold springs are less likely to survive their first few years of life than those born under mild conditions – it seems that cold temperatures lead to reduced birth weights, which in turn lead to lower survival rates.   In general, the data from Rum show that the faster growth and development of stags (see Breeding Biology) makes them more sensitive to environmental conditions and thus more likely to die than hinds; there is some indication that this may be equally true of stag foetuses.

In addition to low birth weights and inclement weather, calves can suffer accidents and are sometimes born with congenital defects that can be fatal, if they are born alive at all.   In their 1979 paper the RDRG biologists note that five (16%) of the 31 calves for which a cause of death could be reliably established were stillborn.   The authors also provide examples of calves born with various congenital disorders including shortened hoof tendons (which cause the feet to curl up and prevent the animal from walking), shortened lower jaw, perforated skull and muscle wastage – all conditions were invariably fatal (typically from malnutrition), although some calves with skeletal defects lived for several months.   The study records other calves that died from various causes, including failing to suckle properly, their mother’s milk drying up, knocking themselves unconscious and drowning while crossing a burn or succumbing to heavy parasite infection (see below).   In his 1977 book Deer in the New Forest, John Jackson notes that “various congenital abnormalities have been recorded in New Forest deer, the most bizarre of which was a red deer born without eyes or eyesockets.”   Mr Jackson doesn’t mention whether the calf survived, but the prognosis doesn’t seem good.   Despite the foregoing, accidental deaths and predation (see below) account for relatively few calf deaths and Dr Lowe found that malnutrition killed the majority (almost 90%) of the unfortunate yearlings.

Much work has gone into assessing the survival rate of calves, but it is also important to look at adult death rates.   As we have seen, if a calf makes it to its first birthday its continued survival is considerably more likely and there is a ‘levelling out’ of mortality (i.e. mortality of two-year-olds, three-year-olds, etc. are roughly the same and ‘absolute levels’ of mortality are fairly low) until the animal reaches old age.   Generally speaking, however, stags are less likely to reach old age than hinds; there are several reasons for this, but perhaps the most apparent is that they undergo the strenuous physiological changes and increased activity associated with rutting – moreover, they are often involved in fights that may prove fatal.

For hinds, survival can be closely linked with the time they first produce a calf.   We have already seen, in the ageing section, how recent work by the RDRG has established that “the rate of senescence in maternal performance increases with early-life fecundity” (the title of a 2006 paper to Ecology Letters).   In other words, the sooner (i.e. younger) a hind produces her first calf, the more rapidly she shows signs of senescence (ageing) after the age of about nine years.   In their various papers on the subject, the RDRG biologists don’t speculate about whether this is likely to translate to an earlier death, but it seems likely.   Data on other animals (including a study, published in the journal Nature during 1998, that looked at a large collection of human genealogical records) has linked, albeit rather tenuously in some cases, low fertility with increased longevity.   The idea is referred to as the ‘disposable soma hypothesis’ -- sometimes also referenced under the ‘umbrella theory’ of antagonistic pleiotrophy -- and while the details don’t concern us here, the basic premise is that reproduction is an energetically costly undertaking and producing a baby diverts resources away from the cellular ‘construction crews’ that maintain and repair the body.   Ergo, the sooner you start reproducing, the sooner this energy budget is exhausted.   Energetic expenses aside, the act of calving can pose a threat to a hind and the RDRG have found that each year a few hinds will die giving birth.   Death during parturition (i.e. giving birth; from the Latin parturire, meaning ‘to be in labour’) is generally uncommon and usually requires abnormal presentation of the foetus, but if the mother is in poor condition and the weather is inclement as many as 44% can die during childbirth.

Fighting, childbirth, population levels and just being very young or old aren’t the only mortality sources that affect Red deer.   Weather is highly significant and the RDRG have found that wet springs and autumns lead to an overall reduction in both adult and calf survival (presumably because high rainfall has a detrimental impact on plant growth and a lot of rain in the autumn thus reduces the growth of grass, and hence food, for the winter).   Road traffic may also represent an important threat and although the first report of the National Deer-Vehicle Collisions Project found that Red deer are involved in fewer collisions than other species (presumably because of their limited distribution), it is estimated that around 1% of the total UK population are killed on roads each year and locally it can be a serious problem.   The subject of deer deaths on roads is covered in greater detail in the main deer article and in the related QA.    

Deer can also die as a result of various accidents, including falls and drowning and are susceptible to items such as discarded netting/twine, poorly maintained fences, snares, barbed wire and, according to Norma Chapman in her book Deer, one (she doesn’t mention the species) was found with a discarded lens hood caught around its leg.   Discarded fishing nets can also be problematic for deer in coastal regions and, in his A Life for Deer, John Fletcher recounts several harrowing stories of deer that had become entangled in fishing wire and drowned or been latched to rocks and starved to death.   Dr Chapman also points out that some deer are killed by trains while crossing the tracks. 

In his review of deer mortality, Dr McDiarmid wrote:

“Deer on the whole, are extremely healthy animals and nowadays we do not have the dramatic ‘die-offs’ which occurred in and before the nineteenth century.   It is worth remembering that serious diseases such as rinderpest [a lymphatic virus primarily affecting cattle], contagious bovine pleuropneumonia [a bacterial infection causing inflammation of the lungs] and foot and mouth disease used to be rife. …  Nowadays our main problems are associated with parasitism…”

Indeed, although free-ranging deer are largely disease-free (most of the data we have come from captive populations), they are susceptible to various parasites and infections.   It is important to recognise that, although the majority of parasitic infections aren’t fatal in themselves (after all, it’s seldom in the parasite’s best interest to kill its host), during the winter and early spring, when a deer may be malnourished and battered by the elements, parasites can be an additional drain on the animal’s resources – this can be a ‘tipping point’, overwhelming the animal and leading to its death.   Owing to the potential zoonosis (i.e. diseases that can be transferred to humans) of certain deer parasites and diseases, the subject is discussed further in the Interactions with Humans section.

Finally, and to a lesser extent in the UK, predators can influence deer survival.   To the exclusion of humans, there is only one predator in the UK that is probably capable of bringing down an adult Red deer: the Golden eagle (Aquila chrysaetos).   Golden eagles will take calves and have been seen attempting to chase adult deer over cliffs; I have seen a video of a captive eagle chasing and killing an adult Roe deer and eagles were recently filmed by the BBC (as part of their Life documentary series, although the footage was unfortunately left out of the final cut owing to the distance the camera crew were from the action) hunting Reindeer (Rangifer tarandus) in northern Finland.   There are few data available on how significant eagles are as predators of deer, but in his 1969 paper Dr Lowe estimated that, based on bruises in the meat of carcasses, just over 13% of calf deaths were caused by eagles.   In Europe, Grey wolves (Canis lupus), Lynx (Lynx lynx) and Brown bears (Ursus arctos) may take deer as, occasionally, do wolverines (Gulo gulo).   A study on the diet of lynx in Poland’s Bialowieza Primeval Forest between 1985 and 1996 revealed that these cats killed between 42 and 70 deer per hundred sq-km, which represented between 6% and 13% of the total spring population.   The study, published in the journal Acta Theriologica during 1997, also found that although wolves and hunters took more deer each year, lynx most often targeted calves and similar studies elsewhere have shown that Red deer calves can be an important component of a lynx’s diet.

Calves are vulnerable to dogs and potentially other smaller carnivores – red deer meat has been identified in the diet of buzzards, foxes, badgers and pine martens, although it is unclear how much represents direct predation and how much is scavenge.   In his fascinating 1999 book Kia: A study of Red deer, Ian Alcock, talks of the ‘intrinsic aggression’ that Red deer hinds show towards foxes and writes:

“Foxes may kill a few Red deer calves during their first day or two, but probably after that the calves are too big for them to tackle.”

I have come across a couple of casual references to wild boar (Sus scrofa) being predators of calves, although I have been unable to track down a source for them.   Nonetheless, wild boar are more than capable of killing a deer calf and have been known to take small mammals such as field mice and young rabbits if the opportunity presents itself.   However, wild boar biologist Dr Martin Goulding recently told me:

“I am not aware of a reputable, or even anecdotal, reference reporting that wild boar will predate deer calves. There is plenty of evidence that wild boar will eat road kill deer, and wild boar are reported in eastern Europe to have driven lynx away from their deer kills.”

Calves may also be killed by their mother and at least one death on the North Block of Rum during the mid-1970s was attributed to attack by feral ponies.   Outside of the UK and excluding man, wolves are probably the most significant predator of deer and there has been some work recently looking at the physical condition of the deer taken by wolves.

Between 1984 and 1988, Henryk Okarma of Jagiellonian University in Poland studied the carcasses of 90 deer killed by wolves during winter in the Carpathian Mountains of southeastern Poland.   Dr Okarma found that wolves predominantly killed calves and hinds, representing 44% and 40% of the total respectively – stags were only represented in 16% of carcasses.   The majority of calves were taken by wolves in the late part of the winter (i.e. February and March), with calves consisting 32% of kills in early winter and 51% in late winter – adult hinds were killed in roughly proportionate numbers during both periods.   The data also showed that wolves killed ‘prime’ adults -- the average ages of hinds and stags were 7.2 years and 5.3 years, respectively -- with old animals (those of 10 years or above) accounting to only 13% of kills.   From the carcasses, Dr Okarma was able to assess marrow fat content of the animals, and found that adults had highest marrow fat content during the early winter (76% in early winter, 52% by late winter) – calves showed a similar utilisation of fat during the winter months.   Overall, Dr Okarma concluded that wolves affected the young classes of deer more significantly, with calves being particularly vulnerable in late winter, and that hinds were more vulnerable to wolf predation than stags.   Calves are probably more susceptible during late winter because they’ve used much of their fat reserves and begin to lose condition.   Given the pronounced sexual segregation in Red deer outside of the breeding season, it may also be that wolves actively seek female groups with calves – the author suggests that this might explain why hinds seem more susceptible to wolf predation than stags.

More recently, a team of Italian biologists studied the physical condition of Red deer killed by wolves in an area of the western Alps between November 2003 and April 2004.   The data, published in the journal Folia Zoologica during 2007, showed that most of the 14 Red deer killed by wolves were in poor physiological condition, with low levels of fat in the femur (leg) marrow; almost 40% had less than 25% fat content.   The biologists tentatively suggested that, unlike for the sympatric Roe deer which were the primary focus of the study, body condition may have played a role in the wolves’ choice of Red deer prey.   Thus, taking these and other data together, it seems likely that in areas where predation is a significant source of mortality, body condition (and specifically the conditions in which the deer spend the summer and autumn) may play an important role in influencing the likelihood of being killed.

Overall, in Britain, deer that die of natural causes and aren’t killed by another deer, predator or in an accident, die of starvation, exposure, disease/infection or physiological failure (i.e. ‘old age’) – the majority of deaths occur during March and April.   Starvation is often associated with the wearing/loss of teeth in old animals.   In addition, it is worth mentioning that we should be careful not to lump cars and predators together as a source of mortality – cars are entirely unselective in their actions.   Deer populations are also heavily managed by humans and where shooting is employed as a method of control, allowing sickly animals to be killed and thereby reducing competition, natural mortality can be significantly reduced.   The management of deer populations by man is discussed in greater detail in the Interaction with Humans section.   (Back to Menu)

Food & Feeding Behaviour: An interesting collaboration between German anatomist Reinhold Hofmann and Kenyan game biologist D.R.M. Stewart led to the publication, in 1972, of a paper in the journal Mammalia in which the scientists argued that all Ruminants could be split into groups on the basis of their feeding strategy.   Traditionally, ruminants such as deer had been considered either ‘grazers’ or ‘browsers’ according to how they fed.   Drs Hofmann and Stewart proposed that there were actually three groups: concentrate feeders (i.e. the browsers); grazers (eat grass and other roughage); and intermediate feeders (which graze and browse).   Accordingly, the biologists grouped the ruminants such that about 40% (including Moose and Roe deer) were concentrate feeders, 25% (including sheep and cattle) were grazers and the remaining 35% were intermediate feeders, which “choose a mixed diet but avoid fibre as long and as much as possible” – Red deer were included within this group.   In a 1989 paper on the subject to the journal Oecologia, Dr Hofmann re-affirmed these groupings and wrote of the Eurasian Red deer:

“When forage plants lignify [become ‘woody’] these animals switch to ‘browse’ or falling fruit and seeds (‘autumn mast’) and finally reduce their metabolism and food intake as they, like CS [browsers], cannot digest fibrous forage as well as GR [grazers].”

As we shall see, some subsequent authors have questioned these groupings and argued that Dr Hoffman’s conclusions aren’t supportable; however most literature still refers to these three feeding groups.   I will avoid going into morphological and physiological details of the Red deer rumen, but suffice to say that it seems less adapted to the digestion of fibrous forage than in deer typically considered browsers (e.g. Roe deer), although the matter is complicated by the discovery that the lining of the rumen can change its morphology (i.e. its structure and appearance) in accordance with the quality of the diet.    Why does any of this matter?   Well, the amount of fibrous material in the diet dictates how long it takes to break down the plant material and how much nutriment the deer can extract from it.   Food that is high in fibre is slow to digest and difficult to extract nutrients from – for deer, high fibre foods include grasses, sedges, heathers and ferns.   As the fibre content decreases, the ‘digestibility’ increases.   Medium-high fibre plants include tree leaves and shrubs, while herbaceous plants such as the forbs (clover, milkweed etc.) are low-fibre.

Grasses (e.g. Holcus, Deschampsia, Festuca and Agrostis) are the most important food source, comprising the bulk of the diet along with sedges and rushes (e.g. Carex, Eriophorum, Tricophorum etc.).   Indeed, work on the Rum deer has found that they preferentially opted for herb-rich Agrostis-Festuca grasslands (i.e. that comprised predominantly of bent and fescue grasses) over other vegetation types – in the summer they spent 78% of their feeding bouts on this grassland, while in the winter it was 65%.   However, many grasses are only nutritious for a few weeks during the spring and summer; once the grass has flowered, the nutritional value -- which is the protein in the herbage -- is lost.   Consequently, although the deer may continue to feed on grasslands during the late autumn and winter, it typically offers less nutritious forage and the deer often switch their diet to include alternative food sources for the remainder of the year.   Indeed, a study on the diet of Red deer in Scottish plantation forests between 1990 and 1993 showed a clear seasonality in the diet.   Grasses formed 30% to 70% of the rumen contents in summer, while rushes, sedges, heaths, forbs, deciduous browse and conifers made up between 5% and 20%.   During the winter, 30% to 60% of the rumen volume was heaths, mainly heather and blaeberry, with sedges and rushes accounting for a further 30%.

Ferns (e.g. Dryopteris and Blechnum), lichens, tree shoots and buds, herbs (namely forbs such as Galium and Potentilla), shrubs/heaths (e.g. blaeberry and heather, Calluna vulgaris) and bramble are staple during the autumn and winter.   Bramble is an important component of the diet throughout the seasons because it remains green for most of the year and new growth begins early in the spring.   In some areas -- most notably on Rum -- the deer will also feed on seaweed (predominantly Laminaria kelp, Rhodymenia red seaweed and green Fucus seaweed) during the winter, which provides a good source of nutrients and vitamins, including vitamins A, C, E, K, phosphorous, calcium, iron, copper, manganese and folate – it is also a good source of sodium (more information on the deer’s use of seaweed habitat can be found in the Habitat section above).

In woodland habitats, the browsing of tree and shrub shoots may account for 80% of the diet, while grass and heather form the bulk of the diet in moorland.   In her 1991 book, Deer, Norma Chapman refers to a study of Red deer faecal pellets collected in Thetford Forest on East Anglia’s Norfolk-Suffolk border.   The Thetford deer predominantly ate deciduous (e.g. oak, hawthorn, ash, birch and beech) leaves, grasses and bramble in the summer; grasses and bramble were also eaten during the winter, but the proportion of ivy in the diet increased during this season.   Looking at the year as a whole, the study identified more than 21 different plant species eaten by the deer.

In some populations, there is a marked difference between the diet of stags and hinds and during a study on Red deer living on the Glenfeshie estate in Scotland’s Cairngorm Mountains, a team from the Institute of Terrestrial Ecology, headed up by Brian Staines, found that hinds ate more grass and less heather than stags.   The hinds also chose more fine-leaved species, which are easier to digest than the broad-leaved species eaten by the stags.   In their write-up of the study’s findings to the Journal of Applied Ecology in 1982, Dr Staines and his team note that hinds also ate species higher in nitrogen (important for building proteins) than stags, although the overall rumen nitrogen content was the same for both sexes; the stags had large rumens containing lots of lower-nitrogen species, while hinds had smaller rumens with fewer, high-nitrogen, species.   It appears that the areas in which the hinds fed were situated on ‘richer’ rocks (in terms of geology and soil quality) than those in which stags fed and, as such, the hinds opted for quality while stags opted for quantity.

So, why should this disparity in feeding behaviour exist between the stags and hinds?   After all, as Dr Staines and his colleagues note in their 1982 paper, the stags would be nutritionally better off if they fed on the same ranges and species as hinds.   Well, research by the RDRG on Rum has shown that hinds move to more productive grassland prior to commencing lactation; their energy demand almost doubles at the start of lactation and in the weeks leading up to parturition they will double their food intake as a consequence.   Dr Staines and his co-authors point out that small-bodied hinds may be displacing the larger stags from these favoured feeding areas.   The hinds have a smaller and narrower mouth, which allows them to reduce the average sward height to such an extent that the stags, with their larger mouths, can’t feed effectively in the area – in other words, the females crop the grass so tightly that the blades are too short for the males to get at.   So, the stags are forced into areas of poorer quality grazing where they consume more coarse forage.   Fortunately, for the stags, being larger animals means they have a correspondingly larger rumen volume to cope with the coarse diet, which requires them to process a greater quantity of food if they’re to extract sufficient nutrients.   Perhaps Rory Putman put it more eloquently than me in his 1988 book The Natural History of Deer, in which he explained:

“It would appear therefore that stags and hinds are actually selecting different foods, each adopting the foraging strategy appropriate to their body size, mouthpart size and ruminal physiology.”

It is important to note that seasonal and sex-related changes in the diet have not been documented in all populations.   Indeed, dietary studies conducted in Europe and further afield have uncovered different feeding preferences and strategies.

In a paper to the journal Mammal Review during 2001, Claudia Gebert and Helene Verheyden-Tixier, at the French National Institute for Agricultural Research in Toulouse, report on the variations in Red deer diet across Europe based on a survey of 13 scientific papers looking at rumen contents.   The researchers found that these deer ate a wide variety of different plants, counting 145 different species, and that the variation in foods consumed was linked to environmental conditions and habitat.   Surprisingly, despite the seasonal shifts documented by other researchers, this literature review found that only the consumption of seeds and fruit (e.g. acorns, apples, pears, beech-mast etc.) showed any clear seasonal patterns.   Moreover, the amount of grasses and sedges eaten didn’t vary according to habitat, season or sex – they were consumed at a roughly constant level of 29% in all habitats and seasons.   Interestingly, the main finding of this review was that Red deer are primarily concentrate selectors (i.e. they browse more than they graze), with this feeding method accounting for 64% to 72% of their winter diet and 50% to 75% of their summer diet, depending on habitat.   So, while the data generally support the classification of Red deer as ‘intermediate’ feeders because they browse and graze, they don’t succour the argument made by Dr Hofmann that this species switches from browsing to grazing as the seasons change and the plants start to lignify.   In their conclusion, the authors write:

“… Red Deer eat mainly concentrate food and do not switch from concentrate food to grass between seasons.”

Similarly, a survey of the diet of Red deer in the floodplain forests of the Morava River in the Czech Republic between October 2001 and November 2002 by Jarmila Prokesova provides support for these animals being more browsers than grazers, although it did also show some seasonality.   Dr Prokesova found that the majority of the deer’s food (71%) was obtained from the forest in the form of broadleaf tree shoots, leaves, buds and bark.   The highest volume of this woody plant material was found in the diet during April and May.   It seems that the deer had the broadest diets during the late summer and autumn, when they fed on fruits, forbs, grasses and crops (e.g. maize) in fields bordering the forest.   Nonetheless, during all seasons it was the forest that was the most important feeding site for the deer and in his 2004 paper to the journal Folia Zoologica, Dr Prokesova wrote:

“The analysis of feeding behaviour showed that the floodplain forest red deer were browse specialists [i.e. concentrate feeders] in all seasons of the year. Other food sources were less important.”

These studies reinforce the notion that Red deer are opportunistic feeders, eating the plants in proportion to their availability – if grasses are available all year round, and crucially both males and females are able to graze them, they’ll eat grasses all year round.   While their diet is typically dominated by a few staple plant groups, part of being an opportunistic feeder is that you’re able to make the best of the prevailing conditions.   Red deer will graze lichens from tree bark and fence posts and will eat ivy, nuts, fungi, fruit (especially acorns and beech mast), berries and even holly and roses.   Bark is sometimes eaten, generally during the winter months, and affected species include rowan (typically Sorbus aucuparia), beech (Fagus sylvatica), willow (Salix spp.), Norway spruce (Picea abies) and lodgepole pine (Pinus contorta).   Over some parts of their range, bark stripping by Red deer can be a significant problem, especially in commercial pine forests.   This subject is discussed at greater length in the associated Q/A, but the general findings suggest that the activity is not driven by nutritional requirements (stripped and non-stripped trees in the same area have very similar bark compositions), but may help the deer improve its digestive efficiency or get rid of internal parasites.

Finally, Cervus elaphus has earned something of a reputation for carnivory and in the 2007 edition of the Guinness Book of Records, the Red deer holds the record for “Most bloodthirsty ungulate”.   The reason for this unenviable title was the discovery that deer on Rum sometimes kill and eat seabirds.   In 1969, the now former chief warden of Rum, Peter Wormell, published a letter in the Deer journal in which he briefly described Red deer biting the heads off Manx shearwater (Puffinus puffinus) chicks.   The following year, ornithologists found Arctic tern (Sterna paradisea) chicks with cleanly amputated wings and legs, while ringing chicks at a colony on Rum.   A stakeout of the colony revealed that the island’s sheep were biting off the limbs and heads and eating them.   In a bid to get a better understanding of the predation on birds by sheep and deer, Glasgow University biologist Robert Furness studied the tern colony on the island of Foula and the shearwaters on Rum.

Dr Furness scoured the hills for corpses and, between 11^th and 17^th September 1987, he carefully studied the feeding behaviour of the Red deer.   It transpires that the deer only attacked shearwater chicks, never the adults, and the attacks only occurred during the latter part of the chick-rearing period from August to late September.   Moreover, it seems that the deer were primarily interested in the birds’ bones.   On several occasions a hind was observed holding a chick, by its head, in her mouth before vigorously shaking it for a few seconds until the decapitated body fell to the ground.   The hinds ate the head, leaving the remainder of the body untouched.   In one instance, a young stag investigated the remainder of the corpse, severing the skin to remove the leg bones and those from the carpal (wrist) region – there was no significant removal of flesh or feathers by the deer.   All attacks by the deer ended in decapitation of the chick, but not all had additional bones extracted.   The 20 deer in the area killed, on average, two birds per day removing around 12g (about ½ oz.) of bone from each bird and, with an estimated 60 birds killed per season, Dr Furness calculated that each deer could potentially gain 36g (1.3 oz.) of bone during the important pre-rut period.   It seems probable that the deer saw the chicks as a potential, albeit comparatively small, source of calcium in an environment where a staple food (e.g. heather) is typically low in calcium – heather on Rum also tends to be lower in nutrients than the same species growing on more nutrient-rich rocks elsewhere in Scotland.   The results of Dr Furness’ study were published in the Journal of Zoology during 1988, and in the paper he wrote of the phenomenon of deer eating shearwater chicks:

“… it may be an unusual habit, found only in peculiar circumstances where ruminants feed on mineral-deficient vegetation on which ground-nesting seabirds are present in high density.”

Reports of carnivory in Red deer aren’t limited to Rum.   In his riveting 2000 book A Life for Deer, veterinarian John Fletcher describes seeing a deer knock-over rabbits infected with myxomatosis and ‘chew them up’, and others to chew antlers that were still attached to another stag!   Similarly, in his excellent Kia: A study of Red deer, Ian Alcock talks about an Australian friend who told him of a Red deer stag that ate a dead sparrow that it found in the enclosure and, a couple of weeks later, the same deer caught and ate a frog from a small pond in the enclosure.   Mr Alcock also points out that the late naturalist Frank Fraser Darling described deer eating frogs, while, in his 1890 Some Account of Jura Red Deer, Henry Evans wrote that not only will they chew the antlers and bones of dead deer, but large bits of skin have also been found in the stomachs of shot stags.

Before we leave the topic of feeding biology, it is worth taking a moment to consider the deer’s feeding behaviour.   The biology and physiology of rumination is discussed at length in the main deer article, so I won’t reiterate it here.   There are however some aspects of Red deer feeding behaviour that merit a mention.   The first of these is the question of how much a deer can be expected to consume each day.   There are very few references in the literature to the amount of food one might expect a deer to eat in a single sitting.   I presume that this a reflection of several factors including that the digestive system size and morphology can change with season and diet; that there are five chambers involved in the digestive process; and because the amount eaten depends on the size of the animal, the quality of food available and the energetic requirements of the animal and it must thus vary according to both season and location.   Consequently, I feel it is more useful to consider the energetic requirements – that is, the number of calories required.

Calorific requirements are also affected by season and size, but provide a better handle on energetics than stomach volume.   In their contribution to Mammals of the British Isles: Handbook, 4^th Edition, Brian Staines, Jochen Langbein and Tim Burkitt provide rudimentary daily energy requirements of 3,500 kcal (14,700 kJ) and 4,500 kcal (18,900 kJ) for a hind and stag respectively, during winter.   The biologists quote much higher values for summer, with around 9,000 kcal (37,800 kJ) for a lactating hind and 11,500 kcal (48,300 kJ) for a stag.   We can illustrate the seasonality here a little more clearly if we do a little mathematics.   If we take an average stag to weigh about 200 kg (31.5 st), we see that during the winter the stag needs 22.5 kcal (94.5 kJ) per kilogram of body weight.   However, that changes dramatically during the summer (antler growing) months, when the stag needs some 57.5 kcal (241.5 kJ) per kilo.   Obviously this is a very crude comparison, but I think it illustrates the impressive energetic demands that the deer must live with.   Incidentally, if you’re interested in how this compares to an ‘average’ human, the recommended daily calorie intake for an adult male is typically around 2,500 kcal (8,400 kJ), or 2,000 for a female – this increases by 300 – 400 kcal (1,260 – 1,680 kJ) per day during pregnancy.   As an adult male, I weigh about 70 kg (11 st), which means I need 35.7 kcal (120 kJ) per kilo.

We have seen that hinds increase their food intake to correspond with their entry into lactation, but stags also show marked feeding cycles, with both sexes showing a voluntary reduction in food intake during the winter.   In a paper to the British Journal of Nutrition during 1983, a team at the Rowett Research Institute in Aberdeen led by James Suttie report on the effects of winter food restriction on feeding behaviour of Red stags.   The researchers split 12 hand-reared stags into two groups; one was given unlimited access to food and the other was given 70% of the amount eaten by the first group.   The physiologists found that the deer on the restricted diet had reduced overall skeletal growth over those on the unrestricted diet; despite increasing their intake once the restriction was lifted and putting on weight rapidly, the end result was that the unrestricted deer grew larger than the restricted ones.   This study highlights how important adequate nutrition is during the winter months; even though the deer show a remarkable ability to compensate for low winter nutrition by increasing their food intake during the spring, they’re never able to fully ‘make up’ for that lost time.   Dr Suttie and his team suggested that this phenomenon might explain why Scottish hill stags are smaller than those found elsewhere in Scotland and English deer parks.   The biologists also observed two periods of voluntary appetite loss; the first was during the rut and the second, which occurred in early spring, was associated with a resurgence of sexual activity.

A cessation of feeding during the rut is a well documented phenomenon in Red deer and a study of Red deer at Norway’s Songli Research Station, by a team led by Atle Mysterud at the University of Oslo, found that rumen fill was lowest during mid-October, when males are at their lowest weights and female ovulation peaks.   Dr Mysterud and his colleagues propose two theories to explain this lack of feeding: either the deer consider rest to be more beneficial than food (they need rest to compete for females and can’t rest if they’re feeding), or they are energetically drained by the rigours of the rut, which probably means they have a weaker immune system and thus stop feeding because they’re unable to deal with any parasites they might ingest with the food.   The biologists also found that younger stags had higher rumen fills than older ones, with rumen fill declining until the age of about six years, after which rumen fill was low and stable (i.e. seven-, eight-, nine-year-olds etc. all had about the same amount of food in their rumens).   The reason for this is related to the different breeding strategies used by the deer at different ages (i.e. ‘capital’ vs. ‘income’ breeding as discussed in Breeding Biology).

It should be noted that, while an age-specific behaviourally-induced cessation of feeding seems to occur in some populations, the amount of food taken in during any given feeding bout can be affected by age regardless of breeding strategies.   Just over a decade ago (in 1998) Javier Perez-Barberia and Iain Gordon demonstrated that the amount of tooth wear understandably influences the amount of food eaten.   Simply put, as deer get older they wear down their teeth, which makes them less efficient at grinding up plant material; this means that they swallow larger chunks of food than deer with more efficient teeth.   The researchers found that deer with worn teeth ate less per ‘sitting’ and suggest that eating less may be a strategy to compensate for a less efficient grinding mechanism.   The idea is this: larger particles take longer to break down (more accurately, they have a larger ‘surface area to volume ratio’), so it’s better to have fewer of them at a time, so that more time and resources can be devoted to digesting them.   If the rumen was flooded with large particles, the microbial ‘workforce’ would be spread more thinly and each particle would receive less ‘digestive attention’ and thus potentially yield fewer nutrients.

Feeding behaviour often involves standing on hind legs to pick higher twigs and bushes clean, which creates a browse line that can be 180cm (6ft) above the ground.   Once the food has been ingested, the deer will ruminate (i.e. regurgitate the food, at this stage referred to as cud, and re-chew it to further break down the material); the upper limit for rumination is generally assumed to be about nine hours, although most bouts are substantially shorter, lasting a couple of hours.   Complete digestive passage (i.e. from ingestion to excretion) takes two-or-three days.

Breeding Biology: Deer, like all mammals, practise internal fertilization and their reproductive cycle is highly seasonal, being driven by photoperiod (i.e. how many hours of darkness the deer sees over a 24 hour period).   There is a sexually quiescent period during the spring and early summer, followed by a resurgence of sexual activity as the breeding season, formally referred to as the rut, approaches.

Stags undergo a puberty lasting around six months, at which point testosterone secretion begins and the process of spermatogenesis (sperm production) is complete – interestingly, deer spend a similar proportion of their life undergoing puberty as humans [Click here for more]   Data from Rum suggest that most stags start puberty at about nine or ten months old and reach sexual maturity at between one and three years old (depending on conditions), the average being around 16 months; at this point, the reproductive organs will have increased roughly ten-fold from that of the six-month-old calf.   It should be mentioned that although stags are physically capable of mating by 16 months old (i.e. there are sperm in the testes), most will not do so until at least six years old, because prior to this age the stags fail to develop a set of antlers sufficiently large to challenge other males for mating rights.   Additionally, studies on free-ranging Red deer on Rum have shown that most calves will not develop the conspicuous secondary sexual characteristics (i.e. a neck mane, brown winter coat etc.) until their second year of life.   It seems that there is a fairly narrow range of breeding success in free-ranging deer, with data from the Rum population showing that few stags will have much mating success until they’re six or seven years old and most will fail to carry the success into their teens.

The Red stag’s year is heavily influenced by hormones: primarily the androgen testosterone.   Testosterone has a considerable influence on the sexual state of the stag.   Much of the pioneering work on testosterone’s impact was done by Gerald Lincoln, Fiona Guinness and Roger Short during their time in the Red Deer Research Group.   The biologists demonstrated that castration of stags at any time of the year led to the abolition of any subsequent rutting behaviour; implanting the castrates with testosterone in December lead to resumption of rutting behaviour within a couple of weeks, although no rutting behaviour was observed until the autumn if they were implanted during April or June (when the stags are in a sexual hiatus).    When the intact stags were implanted with testosterone, no changes were seen in rutting behaviour, but there was a noticeable increase in aggression.   Castration or administration of testosterone also has profound impacts on the development and cleaning of the antlers such that if a male calf is castrated it will fail to develop pedicles while, if castrated as an adult, the antlers will be lost and re-grown as normal, but will never shed their velvet layer.   If you implant hinds with testosterone they too will develop the pedicles from which antlers grow.   More details on the influence of hormones on antler development and rutting behaviour can be found in the corresponding Q/As.

The deer cast their antlers between March and May -- the precise date is dependent upon age and social rank such that older, more dominant males cast their antlers (often several weeks) before younger ones -- when increasing day length leads to a drop in their blood testosterone level.   Once the antlers have been cast the deer’s testosterone levels remain low, at less than 0.1 nanograms per millilitre (abbreviated to ng/ml, with nano- meaning ‘one billionth’), throughout the spring and early summer and the stags spend their time in bachelor groups feeding and growing a new set of antlers (see Q/A & Behaviour & Sociality).   The low levels of testosterone keep the stag in a reproductively quiescent state from April until June during which time the testes are regressed within the abdomen.

As September draws to a close, the stags move away from their summer feeding grounds on to traditional rutting grounds, called ‘stands’.   Rutting stands are typically areas of nutritious grassland, which attract females who come to feed and lay down the fat to see them through the winter.   The hinds move around in herds that generally consist of family members and travel about the stands at will.   A single stag will ‘lay claim’ to the best quality area, which will attract the most females and he will defend both from other stags.   A given area of grassland may contain several rutting stands, each with its own group of hinds shadowed and protected by a stag – the harems may merge or split according to the will of the hinds.   Indeed, contrary to appearances, it is the hinds that ‘call the shots’ and although the stags may round up any that move away from the main herd, there is little he can do to stop the hinds moving out of his stand.   Fortunately for the stags, hinds seem fairly faithful to their harems and during a study aimed at assessing paternity, Josephine Pemberton and colleagues found that hinds on Rum moved comparatively little between harems visiting, on average, three males during the 11 days when they were most likely to conceive.   Overall, it seems that the hinds are better off in a harem because not only does it offer the possibility of mating with a prime stag, but it also provides them with some respite from other males; studies in the UK and Europe have demonstrated that hinds which are in harems suffer less harassment from amorous stags than those that aren’t.   This may be part of the reason that hinds in Spain’s Doñana National Park move away from some prime feeding grounds to collect at mating grounds where they form harems within the stag’s territory.   A stag will generally take all necessary action to maintain the harem, because the longer he holds it, the more likely he is to mate.

Despite being generally faithful to their harems, hinds do occasionally wander and the females within a harem may show a tendency to spread out across the stand.   In such cases, the hinds become vulnerable to what biologists call “kleptogamy”, which literally means ‘stolen sex’ (klepto- comes from the Greek kleptin, meaning ‘to steal’, while –gamy comes from the Greek gamos, meaning ‘marriage’).   There are generally stags roaming the periphery of the stands and, if they encounter an opportunity (in the form of an unguarded hind or distracted male) they will attempt to mate.   Consequently, where competition is intense a stag can be seen ‘herding’ hinds in his harem; chasing around trying to keep them where he can see them.   However, this behaviour is not as commonplace as is often believed and is seldom observed outside the Scottish Highlands and some deer parks.   Indeed, in his book Deer Watch, Richard Prior wrote:

“The idea of the male rounding up his females like a sheep dog comes from observations of red deer on the open hill in Scotland.   This is not typical behaviour, even of red deer.   It is more or less unique to the Highlands.”

The reason for the frenetic activity of hill deer, which generally isn’t seen in forest dwelling populations, is an important consequence of the environment, as we shall come to in a moment.   The upshot of all this is that, if the hinds do move out of a stag’s stand into the stand of another male, or another stag tries to claim the harem, the males must decide whether to retreat or fight.

Red stags are large, powerful animals with antlers that can represent formidable weaponry.   Consequently, although antler clashes are a familiar image of the rut -- largely because such encounters are impressive and make captivating video and photographic footage -- the decision to fight is not one that is taken lightly and there is a highly ritualised series of behavioural interactions that happen before stags clash.   The aim of these behaviours is to prevent direct physical violence wherever possible, because violence can be costly.   Indeed, early work by the RDRG on Rum demonstrated that a rutting stag will, on average, only fight with rivals five times during the three weeks of the rut.   Despite this relatively low contact rate, Tim Clutton-Brock and his colleagues have estimated that roughly 5% of rutting stags receive permanent injuries -- in the form of broken bones, deep wounds, a gouged eye etc. -- and calculate a 30% chance of a stag being maimed at some point during a typical rutting run; most free-ranging stags can expect to rut for about five seasons.

When two harems get close, or a stag decides to try and approach another male’s harem the two males will challenge one another.   One of the stags will roar and the other will respond.   We shall look at the roaring more closely in a moment, but as Michael Bright says in his 1984 book Animal Language, roaring offers each stag a “reliable, and safe, method of assessing rivals”.   Indeed, roaring may be all that is required and many challengers back down if their roar doesn’t match or beat the roar of the other stag.   In some cases, roaring bouts may be protracted, lasting for an hour-or-more, with the frequency of roaring gradually increasing to three-or-more per minute.   If the two stags have roars that are evenly matched and neither retreats, the animals will begin a ‘stiff legged’ side-by-side strut, known as parallel walking, which can last anywhere from a few seconds to several minutes.   Parallel walking involves the stags moving slowly along the stand, a couple of metres apart, as each assesses the size and condition of his opponent.   The stags will often stop repeatedly to thrash the vegetation with their antlers and roar; this is often accompanied by a jerking of the penis and spraying of fluid (apparently a mixture of urine and semen) onto the vegetation.   If both stags are evenly matched and neither backs down they turn and lock antlers.   Each stag will attempt to push the other off balance in a fight that can last several minutes and typically ends with one chasing the other away; the winner will sometimes attempt to wound his opponent’s flanks with his antlers.   The victorious stag may continue to strut and roar, signalling his victory to his hinds and neighbouring males.

The roaring of the stag is an important, not to mention impressive and (when heard in pitch darkness) somewhat eerie, component of the rut.   Roaring notifies other males of your presence and gives them an idea of your fitness – roaring is an energy-expensive activity, so those who roar at frequent intervals for prolonged periods must be relatively fit individuals.   The acoustics of the roar is what biologists refer to as an ‘honest’ indicator of fitness, which means that it’s not something the animal can ‘fake’ because it is under physiological control.   If you think about your own voice, for example, you can make it higher pitched or deeper, but you can’t make it deeper than your physiology (i.e. the size and shape of your vocal tract) will allow.   In the case of stags, a deeper louder roar signals a large animal.   Of course, this information is not only of use to other stags -- who can decide whether or not to ‘try their luck’ from a safe distance -- it is also an honest signal to females, who use it to judge the best quality males in the area; work by Cambridge University biologist Karen McComb in the mid-1980s found that it may go even further than this.   In a letter to the journal Nature during 1987, Dr McComb presented her data on the impact of roaring on hind reproductive state, which showed that the roaring of stags advanced the date of oestrus (i.e. caused the hinds to ovulate earlier) over the control groups that weren’t exposed to taped roars.   Dr McComb concluded that harem-holding males could improve their mating success by calling regularly.   Curiously, roaring is not only associated with stags; hinds are known to roar in the days leading to parturition, which vet and deer biologist John Fletcher suggested may be a response to a flooding of the brain with oestrogen.   (See Q/A)

In most habitats, clashes between stags are less common than most realise and in forest environments the rut is often a quieter affair, with stags rarely uttering more than the occasional roar (especially on frosty nights/mornings) or, more commonly, just grunting.   The frenetic activity that we see in the Scottish Highlands -- and to some extent in park situations, too -- is a result of the large open expanses of the grasslands.   In forest habitats, tree cover prevents a harem-holding stag from seeing neighbours and he apparently finds it unnecessary to continually proclaim his harem-holding might.   On the hillsides, it’s easier for the hinds to disperse more widely and the stag can see all the other stags in the vicinity and must therefore exert a terrific amount of energy trying to keep his hinds together and see off challenges from other males.   All this activity takes its toll on the stag, which may lose between one-fifth and one-third of its body weight during a fortnight of intensive activity; he must then retire to recover from what Richard Prior rather comically described as a “kingsized hangover”.   Consequently, as the rut advances, the harem-holding stags become progressively more exhausted and the likelihood of them being overthrown increases.   The rutting season may last for six weeks or more, each stag will hold a harem for considerably less than this – from a few minutes to a couple of weeks.

It is interesting to note that some mature, experienced stags appear to convey some form of stability to the rut; this was demonstrated in exciting fashion on British television last year.   During the 2009 rutting season on Rum, the long-standing ‘champion’ of the rut -- as proclaimed by the BBC’s AutumnWatch programme -- Percy (most, if not all the Rum deer have been named by the RDRG biologists) was defeated by the younger stag Cassius following a fight that lasted more than five minutes.   It seems that Percy’s displacement triggered a coup d'état the likes of which the RDRG biologists had never seen.   Many other stags emerged from the metaphorical ‘woodwork’ to challenge Cassius and during a period of a little over an hour, Cassius fought with each stag and won!   This situation provided a fascinating behavioural insight into the mating behaviour of Red deer and aptly demonstrates a crucial point: holding a harem is important.

The biologists of the RDRG have established that a critical component to successful mating for Red deer is holding a harem; without one their chances of mating are low.   The RDRG have demonstrated that, among the Rum deer, stags rarely hold substantial harems (harem size ranges from two-or-three hinds to as many as 70) until they are six or seven years old and few maintain them past 11 years old – stags are most likely to hold harems at between nine and 11 years of age.   This is reflected in feeding studies, which illustrate how stags of different age groups use different breeding strategies.   Biologists typically divide animals into either ‘capital’ or ‘income’ breeders, which basically means that they either rely on fat reserves during the breeding season (capital) or they rely on whatever food is available at the time (income).   In habitats such as Rum, mature harem-holding stags are typically capital breeders; they don’t feed during the rut and survive on the fat reserves laid down during the spring and summer.   Conversely, older and younger animals are income breeders who continue to feed during the breeding period because they’re less involved in challenging ‘prime’ males for mating rights.   Consequently, it tends to hold that prime age males lose the most weight (relatively speaking), while both young and old individuals lose proportionately less.   I should mention that, in my experience, this is not true of all populations, and in habitats where competition is low (e.g. in the New Forest at the time of writing) prime harem-holding stags may continue to feed throughout the rut.

Of course, all of this effort on the part of the stag is aimed at one goal: to mate with the greatest number of females possible, and pass as many of his genes on to the next generation as he can.   Thus, if a stag can defend a group of hinds from the attentions of other males, he has the opportunity to mate with each hind as she comes into oestrus (season).   As the hinds approach oestrus, the male becomes increasingly attentive and displays a behaviour known as flehmen, a phenomenon first described in Red deer by hunter and naturalist Jacques du Fouilloux in 1561.   Flehmen is a German word meaning ‘to curl back the lip’ and involves the stag curling its top lip back to expose the vomeronasal organ (VNO) located in the top of the mouth (see Deer).   The VNO (or Jacob’s Organ) is a fleshy organ used to assess air currents and fluids for pheromones – this explains why the flehmen response is often associated with the stag sampling a hind’s urine.

Early studies of the Red deer on Rum failed to find any evidence of a ‘silent oestrus’ -- where the hind undergoes a physiological oestrus, but no behavioural oestrous (in other words, she ovulates, but doesn’t show any changes in behaviour like she does for her first proper, or ‘overt’ oestrous) -- that is so well documented in livestock.   However, the phenomenon has since become well established in deer, including Reds and has led some biologists to speculate that a silent oestrus may be a trigger for the rut to get into ‘full swing’.   Regardless, studies by Claire Adam at the Rowett Research Institute during the mid-1980s have suggested that the trigger for the oestrous is a rise in melatonin (a hormone produced in the pituitary gland in response to shortening days), which leads to a change in both quantities of, and sensitivity to, progesterone and oestrogen in the hind’s blood plasma.   The precise hormonal mechanisms involved in stimulating oestrous in hinds are rather complex and require further study.   To try and avoid unnecessary confusion (and extending this article by several pages!), I shall deem the topic out of the scope of this article, but in summary Dr Adams and her team were able to show that by giving their captive deer supplements containing melatonin the stag shed his antler velvet and started rutting five weeks earlier than the un-treated stags.   Similarly, hinds administered with melatonin started their first oestrous and ovulation in mid-September, five weeks earlier than those that weren’t given the melatonin.   The initiation of oestrous as a response to the nights drawing in is why deer are sometimes referred to as ‘short day’ breeders.

The specific time at which the female reaches puberty and comes into oestrus depends largely on the environmental conditions and, specifically, the conditions in which the animal overwintered.   In high-quality habitat (e.g. in deciduous forests and parks), hinds reach puberty at around 15 months old, although on the Scottish hillsides and Rum, puberty may not be attained until the animal is three years old.   Studies on both farmed and wild deer suggest that there is a ‘critical’ body weight that the hinds must reach if they are to successfully ovulate and stand a chance of conceiving.   Consequently, hinds weighing less than about 50 kg (110 lbs) rarely calf.   Given that body condition (generally expressed in terms of body weight) is such a critical component to the hind’s fertility, it is not unexpected that hinds wintering in good conditions enter oestrus earlier than those wintering in harsher conditions.   Similarly, hinds living in good quality areas may be able to re-gain sufficient weight after having calved to produce a calf every year, while those in poorer habitats (such as on Rum) may only breed every other year.   Indeed, Tim Clutton-Brock and his colleagues at Cambridge University have demonstrated that the hinds on Rum that successfully raise a calf in a given year -- these are referred to as milk hinds because they have borne the costs of lactation -- often fail to put on sufficient weight by the onset of winter and are more likely to die than those that haven’t calved (so-called yeld hinds, from the old English gelde meaning ‘barren’).   The Rum biologists estimate that about 35% of these milk hinds fail to breed in the following year and the majority of hinds in the Scottish highlands breed in alternate years.   As can be imagined, population density also has a considerable influence on the condition of the hind; more deer equates to less food per animal and a lower probability of reaching ‘critical weight’ in time to breed.   Thus, increasing populations typically lead to reduced breeding success and low calf survival.

Prior to the initiation of the Rum long-term study, little was known about the reproductive biology of deer.   This changed in 1971 when RDRG biologists Fiona Guinness, Gerald Lincoln and Roger Short presented their data, in a paper to the Journal of Reproductive Fertility, on the reproductive physiology and behaviour of Red deer hinds that were caught on Rum as calves and hand-reared.   From this study it was established that hinds came into oestrus during the second week of October; the hind is then receptive for around 24 hours every 18 days-or-so until February or March, or until she conceives.   The biologists noted that, just prior to starting oestrus, the hinds developed a “sweet, musty smell around the tail” and a “second, strong penetrating odour coming from the vaginal mucus”.   Apparently, at the start of oestrus clear fluid mucus could be seen dripping from the vagina and tail, which became increasingly cloudy and viscous as the rut progressed.

As the hind approaches oestrus, the stag will remain within a few metres of her and become very attentive.   During the initial approach to oestrus the hind may shun the stag’s advances, but as she comes into season she may solicit the stag by trotting past with her head held low and neck extended making a characteristic open-mouthed chewing action.   The stag will follow and, in some cases the act of mating may be preceded by a brief chase.   When the hind is ready, she will stand still in front of the stag with her back slightly arched, her ears back and her tail raised, at which cue the stag will mount her.   In their 1971 paper, Dr Guinness and her colleagues wrote of the mating:

“After mounting, the stag would pause momentarily to achieve intromission [penetration].  Then, after a few mild pelvic thrusts, he would lunge violently upwards from his hind quarters so that his legs left the ground and his body assumed an almost vertical position.  The force of his ejaculatory thrust usually pushed the hind forward a few paces, and the stag dismounted in the process.”

A similar description of the mating procedure is given by John Fletcher (who worked with Dr Guinness and her team in the late 1960s and early 1970s) in his fascinating book A Life for Deer, in which he wrote:

“Eventually, late in the rut, the hinds will stand, and after some nervous clumsy attempts the stag will rapidly come to ejaculation, and presumably orgasm, and with one colossal thrust lifts all his four legs off the ground and push the hind forwards.”

The hind will continue to ovulate every 18 days until she is successfully mated and Dr Fletcher goes on to mention how the intensity of the hind’s oestrous behaviour grows with each successive cycle: at the start of October, the oestrus is barely perceptible to the human observer but, come December, if she hasn’t been mated, the hind is “rampant with overt urge to be mated and solicits the stag shamelessly”!   In their 1971 study, Dr Guinness and her team noted that when hinds were prevented from becoming pregnant, some continued to come into oestrus until March, undergoing as many as eight cycles.

Once successful copulation had been completed, the biologists observed that the stag often stood, roared and urinated, while the female either stood for a few minutes with her back arched and ears flat straining her abdominal muscles, urinating and defaecating, or she would resume grazing.   Following ejaculation, the stag wouldn’t attempt to mate again for at least another 20 or 30 minutes.   Cervus elaphus is a polyandrous and polygynous species, meaning that neither sex show any monogamy, although they may mate with the same partners on several occasions.   In some instances, a hind may be mated by several different stags during a single oestrus, but in general she will mate only once per oestrus.   Whether or not a hind becomes pregnant depends upon the conditions: in areas of low deer density (where there is more food per head) between 25% and 67% of the yearlings can become pregnant, while in the favourable conditions offered by many lowland deer parks the yearling pregnancy rate can be 90% or higher.   There also appears to be a considerable synchronicity of conception; in his 1999 book Kia: A Study of Red Deer, Ian Alcock points out that:

“around 75% of wild red deer hinds [presumably on Rum] conceive within about a three-week period at the end of October.”

Work in Scotland and elsewhere has demonstrated that the majority of hinds (up to 85%) conceive during their first oestrus, if successfully mated.   Gestation lasts for between 225 and 245 days (7.5 to 8 months) and in the 1971 Rum study, the average was 231 days.   The gestation length varies considerably among the proposed subspecies of deer and some fascinating crossbreeding studies have revealed that hinds gestating hybrid foetuses have gestation periods intermediate between the two parent subspecies.   Such results fostered the notion that the length of gestation in Red deer was genetically fixed, within narrow limits.   However, recent work by a team of New Zealand biologists, headed up by Geoff Asher, and a team from Spain’s Universidad de Castilla-La Mancha, fronted by Andres Jose Garcia, have uncovered compelling evidence to the contrary.   The studies have shown that both nutritional state and date of conception can affect the length of the gestation.   Hinds conceiving early in the season tended to have longer gestation periods than those conceiving later – Dr Garcia and his team proposed that this may help reduce the likelihood of out-of-season births.   Similarly, Dr Asher and his colleagues have found that well fed hinds had shorter gestations than those on a lower quality, or restricted, diet – the quality of the nutrition seems to be most important during the third trimester of pregnancy, during which the developing calf puts on the most weight.   The biologists speculated that it may be desirable for hinds to devote the effort to ensuring that a fully developed calf is born, even with the added expense of a longer gestation.   There is also some evidence to suggest that pregnant hinds which fail to reach the necessary condition early on in the rut may resorb the foetus.   Thus, overall, it seems that nutritional state (especially late in gestation) is probably a more significant driver of protracted gestation than the date of initial conception, but more work is needed to clarify the relationship.

During the latter part of pregnancy, the hinds tend to spend much of their time resting; in captivity they may be seen pacing the fences more than at other times of the year.   In some instances increased aggression has been documented just prior to giving birth, while others have recorded bellowing in a similar manner to a stag during the rut.   Indeed, in his A Life for Deer, John Fletcher tells of how hinds “roar like stags in the few days prior to parturition” and he suggests that by this stage the hind’s progesterone (the hormone that gets the womb ready for, and maintains it during, pregnancy) levels have fallen, exposing her brain to the full force of oestrogen.   Dr Fletcher’s Ph.D work on the Red deer of Rum showed that oestrogen mimics testosterone, acting to stimulate roaring in both sexes.

When the hind is ready to give birth, she will leave the main herd and move to an area peripheral to her normal range (i.e. where she spends the majority of her time) to give birth in isolation – a hind may calve in the same general area over successive years, but it is apparently rare for the exact same site to be used more than once.   The hind may leave the herd at any point from a couple of days to a couple of hours before parturition; in a paper to the journal Behaviour during 1975, Tim Clutton-Brock and Fiona Guinness report that, on Rum, the hinds usually left their matriarchal group between two and 12 hours prior to calving.   A team of biologists headed up by Tim Birtles, the operations director of Tatton Park in Cheshire, has documented the calf site selection by Red deer in two deer parks and a deer farm in north-west England.   The results of the study, published in the journal Animal Welfare during 1998, show that “areas of obvious plant cover were selected in preference to open ground” and although this did vary with the habitat, the biologists concluded that “cover appeared to be a primary requirement for calving”.   Similar data have been obtained from wild deer and the RDRG have also noted that hinds on Rum tended to move to higher ground, where deer densities are lower, just prior to calving and remain there until the calf was old enough to join the herd (around two weeks old).

Shortly before parturition there is a noticeable swelling of the hind’s udders and vulva.   In two papers to the Journal of Reproduction, Fertility and Development during the mid-to-late 1970s, Pamela Arman at Aberdeen’s Rowatt Research Institute and her colleagues described in detail the calving and maternal behaviour of penned and free-ranging (farmed) tame Red deer.   In the penned deer, Ms Arman found that labour lasted around 40 minutes, from the appearance of the amniotic sac to the birth of the calf – during labour the animals were restless, standing up and lying down alternately.   Ms Arman witnessed three births during which two hinds calved standing up, and the third lying down.   Ms Arman, along with two colleagues, subsequently described the calving of 27 free-ranging farmed deer, among which parturition lasted an average of 1 hour 47 minutes, with the placenta being released just over 1 hour 30 minutes after calving.    In 79% instances, the hind gave birth lying down and in 88% cases, presentation of the calf was normal (i.e. front feet first, then the head); only one calf was abandoned when the hind was disturbed by a keeper bringing the morning feed.   From the observations of Ms Arman and her colleagues it appears that the hinds are primarily attracted to the smell of the placenta and afterbirth, which they immediately eat (presumably as an anti-predator mechanism), even at the expense of the calf.   In one case, a hind in the free-ranging group was seen to stagger into a stream where she dropped the calf before stepping out to clean-up the fluids; the authors wrote that the calf “would have become chilled and drowned but for rescue by the observer”.   On Rum, the new mothers (called “dams”) have been observed to eat the afterbirth, placenta and any grass stained where it fell.

Typically, Red deer give birth to a single calf; twins are rare.   In his A Life for Deer, John Fletcher notes that under conditions of plenty (e.g. in a deer farm or managed deer park), as many as 1% of the hinds may give birth to twins, while only about 0.1% of Scottish hillside hinds have twins.   As with conception, birth times appear to be highly synchronised and during a study of hinds at Kilmory Glen (Rum) during 1974, Tim Clutton-Brock and Fiona Guinness found that nearly 70% calved in the three weeks between 25^th May and 14^th June, with just over one-quarter of all births taking place in the week of 1^st to 7^th June.   These findings are in line with other studies, which have found that Red deer in the northern hemisphere have a short calving season, running from late May until mid-June, with the majority of births taking place during the first and second week of June (although there have been reports of fully developed foeti in December and calvings in January!).

The weight of the calf at birth varies according to the habitat, condition of the mother and the sex of the calf.   Ms Arman and her colleagues reported male calves with a mean weight of just over 6.5 kg (just under 14.5 lbs), while female calves averaged 6 kg (weights were once the calf was dry and had suckled for the first time).   Birth weights reported elsewhere in the literature range from 6 kg to 11 kg (24 lbs).   On Rum, the RDRG have found that the birth weight of calves was closely related to the average daily temperature during April and May – when temperatures were higher (i.e. between 9^oC and 10^oC; 48 - 50^oF) birth weights were higher than in years when the temperature was between 6.5^oC and 7.5^oC (44 – 46^oF), presumably because grass growth is advanced by warm springs.   It seems that, on Rum at least, although population density can influence birth weight (with smaller calves being born when deer numbers are high), the climate exerts a stronger influence.

Taking the Kilmory and captive data in concert, we can construct a reasonable postnatal timeline of the behaviour of the dam and her calf.   The captive observations showed that the first suckling took place after about half-an-hour, while the hind was lying down, and lasted between 45 seconds and four minutes, during which time the calf took between 150 ml and 600 ml of milk; the calves were able to stand within about 45 minutes of birth.   Drs Clutton-Brock and Guinness noted that, in the first few hours following birth, the hinds remained within about 50 m (164 ft) of their calves, after which they spent much of their time more than 100 m (328 ft) away – some were observed feeding more than a kilometre (just over half-a-mile) away from their calves.   The biologists also found that the hinds were more frequently alerted while feeding away from a hidden calf (i.e. they were more ‘wary’); if accompanied by a calf less than 21 days (three weeks) old, they increased their ‘circle of fear’ (i.e. the observers couldn’t get as close as they could before the calf was born).   It seems that when the calf was more than 21 days old, the hinds returned to their pre-calving level of alertness; hinds were also less wary when their calves were lying down than when they were standing up.   The calves are born with their hooves enclosed in yellow cartilage (sometimes referred to as ‘golden slippers’), which protect the mother’s womb and wear away during the first couple of days following birth.

The notion that it is perfectly normal behaviour for the dam to leave her calf in a suitable ‘hiding place’ (typically an area of long grass, or woodland cover) while she moves off to feed is important to recognise.    There are countless examples each year of people ‘rescuing’ a deer calf that they have found lying on its own, believing it to have been abandoned by its mother.   There is little doubt that some calves are orphaned (especially in areas where deer are at risk from predators) or abandoned by their mother; the latter of these seems most likely soon after birth, before the calf can suckle and death is usually rapid.   However, in her book Deer, Norma Chapman points out that true deer orphans are very rare.      Rather ironically, a person acting in what they assume is the best interest of the calf may actually cause it to be abandoned; the dam may reject the calf if it carries the scent of a human.    The advice from the major animal welfare charities and deer biologists alike is, if you find a calf lying on its own, unless it appears in need of veterinary attention, leave it where it is and do not attempt to touch it – the mother will be somewhere nearby.   Indeed, the mother will return to feed the calf periodically.

It should be noted that calves choose their ‘hiding spots’ carefully, generally opting for long vegetation in sheltered spots and often on raised ground when very young.   The RDRG found that, as the calves grew older they were more frequently found lying on the short grass of the greens, at sites where they weren’t sheltered or raised.   The calf remains in one of its various hiding spots until late September or early October, when the longer hairs of the winter coat starts to grow.   The hind pays close attention to her calf’s the choice of hiding spot.   In his 1999 book, Ian Alcock noted that Kia (a hind in his care) called to Juno (her calf), lying nearby, periodically with a “squeaky grunt” that was clearly loud enough to be heard by the author at about 200 yards (600 ft) away.

Drs Clutton-Brock and Guinness noted that most of the hinds made daily trips away from their calves to feed, returning two or four times per day to suckle them (the calf may be suckled five to ten times per day).   Stag calves are suckled more frequently than hind calves, although there is also a close relationship with the vegetation quality – in areas where forage quality is poor the calves are suckled less often.   A series of experiments on deer imported to Mexico from New Zealand have provided an insight into suckling frequency under conditions of plentiful food.   A team of biologists at the Universidad Nacional Autonoma de Mexico found that the calves suckled more frequently as they got older, although the average time spent ‘per suckle’ declined.   Some of the calves started eating solid food (in the form of cut grass mix put into their pens) at about eight days old, although they didn’t start ruminating until they were around 20 days old.   Similar data have been gathered from wild deer, showing that within the first few weeks of life, a calf will suckle around six times per day, declining to three times or fewer per day by the time the calf is two months old.   Interestingly, however, data from wild deer suggest that the lower frequency of suckling events is counterbalanced by longer durations of suckling (i.e. the calves suckle less often, but spend longer per suckle); presumably the confinement of captivity makes it easier for the calves to suckle ‘little and often’.   During the Mexican study the researchers observed allosuckling, where a dam allowed a calf that wasn’t her own to suckle from her and, at one point, 14 out of the 20 hinds in their herd were nursing calves that weren’t theirs.   In all cases, the allosuckling bouts were less frequent and shorter in duration than filial nursing (i.e. mother nursing her own calf).   The dam will lick the urogenital opening of the calf as it suckles, to stimulate it to empty its bowels; she then eats the faeces and urine.

Having access to sufficient milk, and milk of a suitable quality, is crucially important for the developing calf.   Milk yield and quality seems to be dependent upon the hind’s condition and, according to recent work on captive deer in Spain, the subspecies of the deer in question.   It transpires that Scottish hinds (Cervus elaphus scoticus) are not only larger than their Iberian (C. e. hispanicus) counterparts, but also drop heavier calves that grow more rapidly on a diet of milk that is richer in protein.   In 1975, Pamela Arman and three colleagues from the Rowett Research Institute in Aberdeen published a paper in the Journal of Reproduction and Fertility, in which they documented the components and yields of Red deer milk.   The researchers found that well-fed hinds could produce up to two kilos (just under 4.5 lbs) of milk per day during early lactation; the lactation period varied from 190 days (just under 7 months) to more than 280 days (10 months).   The total yield during the first 150 days (5.5 months) was estimated to be between 140 kg and 180 kg (309 – 397 lbs) in the well-fed hinds and 65 kg (143 lbs) in an underfed hind.   Ms Arman and her colleagues found the red deer milk to be very rich and noted that the composition changed as lactation progressed.   As the calf grew, the fat content increased from around 7% close to the start of lactation to 13% 140 days in, while the protein increased slowly from 7% to 9% over a period of about 180 days.   The increase in solids with progressing lactation led to a marked increase in the energy value of the milk.   The biologists also found fairly high levels of calcium and phosphorous (important bone-growing nutrients) in the milk; their data also point to a rapid replacement of colostrum (the first milk produced, high in fat and white blood cells) with normal milk, complete by the third day of lactation.

In 1987, R.M.F.S. Sadlier wrote of how deer typically produce milk from the food ingested on the day, rather than mobilising body reserves.   This fits in well with observations from Rum and elsewhere that lactating hinds tend to seek out grazing areas offering the highest protein content, because protein is crucial to the growth and development of the calf.   Indeed, there are several studies that show how, if a hind fails to maintain sufficient protein content in her milk, her calf suffers reduced growth, which can have a dramatic influence on its survival.   Indeed, in their 1982 book Red Deer – Behaviour and Ecology of Two Sexes, Drs Clutton-Brock, Guinness and Albon write:

“The growth rate of calves during the first six months of life is probably the principal determinant of the size at which they enter winter and is likely to affect both their chances of survival and their body size as adults.”

As lactation wears on, the calf becomes less interested in suckling and the hind typically seems less patient during periods of suckling; some authors report the hind walking away mid-suckle.   The calf is suckled for six to ten months (they are typically weaned by about eight months old) and is usually independent by the time it’s a year old, although data from Rum has shown that, if the hind fails to conceive during the following rut, she may continue to suckle the youngster until it is a year-or-so old.   Observations on captive deer have documented calves eating soil, which some have suggested is a way for the calves to obtain their gut microbes, while others point to a possible mineral deficiency.

The calf may begin to follow its mother at between seven and 10 days old and as the hinds return to their normal feeding grounds, the calves may form crèches.   On Rum, the RDRG have found that the calf is generally seen within 10 metres (33 ft) of its mother but in their 1982 book Dr Clutton-Brock and his colleagues note that it was “unsafe to assume that the hind closest to a calf was necessarily its mother.”   Parental care is entirely maternal and the hind receives no paternal input during either gestation or suckling.

Much deer research on Rum has focused on the sex ratio of calves, because it reveals some interesting features of deer population biology.   As we have seen, stag calves tend to be born heavier than hind calves; they also grow more rapidly, which means they require more milk and this puts a greater strain on the dam than a hind calf would.   The more rapid growth rate of stags means that they’re more sensitive than hinds to food shortages.   We shall see later on (see Behaviour and Sociality) that there is a marked, almost linear, social hierarchy within deer herds – in other words, there’s a pecking order with a hind at the top, one at the bottom and the rest arranged in between.   A consequence of this hierarchy is that dominant animals tend to have access to more food and food of a better quality than lower ranking individuals, which leads to dominant animals generally being larger and in better condition come the rut.   The years of uninterrupted study of the Red deer on Rum has allowed the RDRG to observe that high ranking hinds tend to have more sons than lower-ranking females.   The sons of dominant hinds also tend to be more successful (i.e. hold larger harems and sire more offspring) than stags born to low-ranking hinds – this is because the dominant hinds are better able to meet the energetic demands of the growing stag, while lower-ranking hinds generally produce weaker sons.   Overall, the trend that the RDRG have observed is for females that produce stags rather than hinds to be more likely to die during the following winter (because they’ve not had chance to put the fat back on following lactation) and, even if they survive, they’re less likely to successfully rear a calf next year.   Indeed, the RDRG have established that hinds producing male calves come back into oestrus, on average, 11 days later than dams that produced a female calf the previous year.

Purely in terms of genetics, a mother is better off producing sons if she can ‘afford’ to and there are two primary reasons for this: first males tend to disperse sooner and further than females, so they don’t hang around, adding pressure to the local food resources; and secondly, males can potentially sire more offspring than females can and thus the mother’s genes have a better chance of making it into subsequent generations.   As we have seen, this seems to be the case with Red deer…to a point.   In a fascinating paper to the journal Nature more than a decade ago (1999) some of the RDRG biologists presented their data on how population density affects the sex ratio of these deer.   The authors, lead by Loeske Kruuk at Edinburgh University, found that as the number of deer in the population rose, even dominant hinds were less likely to produce stags; they also observed that as winter rainfall (i.e. that between November and January) increased, so the likelihood of a hind producing a stag calf decreased.   Similarly, the biologists found that hind fecundity (i.e. how likely she is to produce a calf) declined as the population density increased and with increasing winter rainfall.    Why should this be?   Well, more deer per unit area means less food per deer and higher rainfall is not conducive to good grass yield – consequently, both factors impose what biologists call “nutritional stress” on the deer.   Even under such nutritional stress, the previous observation that dominant hinds are more fecund than subordinates held and the biologists wrote:

“dominant females were consistently more likely to calve in a given year than subordinates, but at low densities the sex ratio of their offspring differed.”

In other words, at high densities both dominant and subordinate hinds tended to produce female calves, while at low densities the dominant hinds had more stag calves, while the subordinates still had more hind calves.   The relationship between fecundity and population density came as no surprise to the biologists, because previous work by the RDRG has shown that, although the time of mating isn’t dependent upon social status, the function of the corpus luteum appears to be, with the effect of breeding being suppressed in low-ranking hinds.

I have touched on the theory of the ‘disposable soma’ earlier in this article and although I don’t wish to delve too deeply into it, I feel it should be mentioned briefly here.   The theory goes that breeding is an energetically costly exercise and diverts resources that would otherwise be used for repairing and replacing damaged and worn out cells elsewhere in the body.   The result, as a team of RDRG biologists fronted by Cambridge University scientist Daniel Nussey has discovered recently, is that females that start breeding earlier show signs of reproductive senescence earlier than those that have their first calf later in life.   In other words, hinds that are ‘past their prime’ (and this prime is reached earlier in early breeders) may continue to breed, but their calves tend to be smaller, weaker and less likely to survive than the calves born to younger females.   The biologists have also found that hinds born in hard times (i.e. when competition for food is high) senesce faster than those born in times of plenty.   As Dr Nussey and his colleagues put it in their paper to Current Biology in 2007:

“A female’s probability of producing a calf in a given year declined more rapidly in old age amongst females that experienced harsh early environments.”

Stags also show a decline in fecundity beyond about 10 years old, at which point they show reduced breeding success, holding fewer and smaller harems and ultimately siring fewer calves.   This reproductive senescence is more pronounced in stags than hinds.   Overall, the pattern is that, on Rum at least, the average hind raises four calves during her lifetime (although some won’t raise any, while others may raise as many as 13), while the average stag sires six offspring (ranging from zero to 24).   In captivity, some deer have continued to produce calves (albeit at a much reduced rate) up until 19 years old, when there is apparently a cessation in reproduction, even if the hind lives for longer.

The final aspect to consider before leaving the subject of reproduction is that of inbreeding.   In evolutionary terms, inbreeding (that is, breeding with a family member) is typically a poor survival strategy, because it reduces the potential for ‘fresh blood’ (more specifically fresh genes) entering the gene pool and makes it less likely that the offspring will be able to cope with environmental changes.   In some cases, this lack of genetic variability (geneticists call such genetic variability “heterosis” or “hybrid vigour”) can also lead to problematic genes -- those that code for diseases, for example -- building up in the gene pool, which can prove debilitating, if not fatal.   So, breeding with those outside of your family (known as “outbreeding”, for obvious reasons) typically allows for a more diverse gene pool and this is good – there are, incidentally, examples of where this isn’t true (type “outbreeding depression” into your favourite search engine, if you’re interested), but that need not concern us here.   The details of this subject are outside the scope of this article, but it’s fair to say that the genetic inheritance a deer receives from its parents is important.   I won’t go any further into the specifics, but suffice to say work by Josephine Pemberton and RDRG colleagues during the mid-to-late 1980s has established that the combination of genes a calf carries in its genome (genetic ‘blueprint’) can determine how likely it is to survive; some combinations benefit stags, while others benefit hinds.   It also affects their long-term breeding performance and in a 2000 paper to the Proceedings of the Royal Society of London, some of the RDRG biologists report that outbred deer had greater ‘lifetime breeding success’ -- i.e. sired/raised more calves -- than their inbred counterparts.

‘Will a stag breed with his mothers, sisters and/or daughters?’ is probably a question fairly often asked of deer biologists.   It is certainly true that rutting stands tend to be used year-on-year and that hierarchical relationships within female groups are fairly stable.   If we couple this with the observations that hinds show a high degree of natal philopatry (i.e. they tend not to move far from their birthplace) it is not difficult to see how a stag could end up mating with his relatives and, as we have seen above, this does sometimes happen.   However, genetic analysis of the Rum deer using repeating sections of DNA called microsatellites has revealed that close inbreeding -- i.e. mating with mothers, sisters and daughters -- is relatively rare among these deer, suggesting that there is reasonable mixing of populations on the island.   Further weight is added because the biologists who conducted the study were unable to assess paternity (i.e. identify the father) in 35% of cases, which ties in nicely with the fact that at least 35% of stags are known to immigrate into their study area (North Block) solely for the rut.

Overall, the genetic work on the Rum Red deer has shown that there is relatively high mixing between populations, with stags and hinds being drawn to the rutting stands every autumn.   The RDRG have also established that few calves are fathered by males using what they refer to as “sneaky” strategies; even though young males may gather in the vicinity of an established harem and try to herd them away, it seems that the hinds avoid mating with these kleptogamists.  (Back to Menu)

Antlers: The growth and formation of Red deer antlers is a complex process that appears to be a case of modified endochondral ossification (i.e. a cartilage ‘model’ is turned to bone); they may reach 90 cm (3 ft) in length and weigh 3 kg (6.6 lbs) each, although 70 cm (2 ft 4 in.) and 1 kg (2.2 lbs) is more common.   During their development, the antlers are soft and vulnerable to damage and covered in a grey-to-purple coloured membrane referred to as velvet.   The velvet carries nerves and blood vessels to the developing antlers and, should the velvet become damaged, the antlers can become deformed.   The antlers have androgen (male sex hormone) receptors and it appears that an increase in testosterone levels in the stag -- probably related to increasing day length -- causes a cessation of the velvet’s blood supply, and it dies and dries out – at this stage, dry velvet can be seen hanging from the stag’s antlers and he is said to be “in tatters”.   Dry velvet is usually removed by rubbing the antlers against trees and bushes – this generally happens during July and is a process known as “cleaning”.   During this rubbing, the antlers become stained with tannins and sap from the trees and saplings, causing the antlers to change from white to a polished brown colour.

The rate of antler growth varies according to conditions, but may be as high as six centimetres (2 ½ inches) per day in mature stags living in good conditions.   A mature stag may well have 12 to 15 branches (called “tines” or “points”) to his antlers; stags are often named according to the number of these points.   Antler development typically begins at around 10 months of age and by his second year a stag will, provided the conditions are good, have his first “head” – these are short, simple, unbranched antlers and at this point he is referred to as a pricket.    Over subsequent years, the antlers should become progressively larger and branched (up until the stag is about 10 years old, after which the number of tines starts to decline), although the number of tines is an unreliable indication of age.   A Red deer with 12 points (six per antler) to his antler is called a Royal stag, while 14 points make an Imperial stag and an animal with 16 points or more is referred to as a Monarch.   In his article for South Coast Today (a Massachusetts news and current affairs website), outdoor writer Marc Folco describes how hunters speak in terms of “pointers”.   Mr Folco explains that a deer with five tines each side is a five-pointer, while one with six either side is a six-pointer.   In cases where the antlers are asymmetrical (i.e. different number of tines each side), the two values are given separated by an “X” – thus, a deer with six tines on one antler and five on the other is a “6 X 5”, rather than an 11-pointer.

The antlers -- which are fully developed and cleaned by August -- are used during rutting; they are employed as weapons with which to fight for access to hinds.   Come March or April, increasing day length triggers a reduction in the amount of circulating testosterone, which causes the antlers to be shed and the cycle to begin again.   The time of casting seems to be fairly stable, at least for some stags – in his excellent book WildGuide, Simon King mentions that one old stag he knew cast his antlers on or about 15^th March each year for eight years.   Shed antlers and velvet represent a veritable goldmine of nutrients for many animals, including both sexes of deer – they contain many of the common essential elements including calcium, phosphorous, sulphur, magnesium, potassium, sodium and iron amongst others.   The velvet also contains various amino acids, including all eight essential ones (i.e. those that are required in the diet and can’t be synthesized by the animal).   Consequently, it is not uncommon to find deer chewing on an antler or velvet they (or another deer) have recently shed.

More comprehensive details of the structure and formation of antlers, as well as a discussion of the various theories proposed to explain their evolution can be found in the antler QAs.  (Back to Menu)

Behaviour and Social Structure: Red deer are gregarious mammals, often associating in family groups.   Early work looking at the social systems and group structures of Red deer (during the late 1930s through until the mid-1970s) yielded mixed results; some have pointed to fairly stable (principally familial) groups, while others have suggested that any ‘ties’ are irregular and group membership fluctuates on a daily basis.   More recent studies on this species in almost all conditions (island populations, mainland populations, captive animals etc.) have started to clarify the situation and it’s painting a fascinating picture.   We now know that Red deer have a highly flexible social system that varies according to the habitat and time of year, as well as the age and sex of the animals involved.   That which follows is a summary, but the reader is directed to the excellent 1982 book Red Deer: Behaviour and Ecology of Two Sexes, by RDRG biologists Tim Clutton-Brock, Fiona Guinness and Steve Albon.   The book is fairly old now but still provides a fascinating and in-depth grounding in Red deer sociality on Rum.

There is a distinct sexual segregation among Red deer that appears to vary geographically; almost all stags on Rum, for example, can be found in so-called ‘bachelor groups’, while studies on Crimean Red deer have shown that only 20% to 30% of stags are likely to be found in bachelor groups.   Some researchers have observed that sexual segregation breaks down when artificial feeding stations are provided, although this doesn’t seem to be the case for all populations.   The data from Rum have shown that, although stags may be seen in groups of females, it is generally rare for stags more than three-years-old to associate with hind groups.   In their 1982 book, the RDRG biologists note that most of their hinds spent between 80% and 90% of their time in groups without stags older than three years and only 10% to 20% of mature stags associated with hinds outside the rut.   The exception seems to be if the stag is castrated; research from Rum has shown that orchiectomized (another word for castrated, from the Greek orkhis, meaning ‘testicle’) stags associate more closely with their dams -- adopting a core range coinciding with that of hers -- than ‘intact’ stags.   The RDRG have found that there is an obvious close bond between the dam and calf during its first year, which tends to degrade as the hind approaches her next oestrous – it appears that this initial level of mother-calf ‘closeness’ is never regained, although if the mother is barren in the following year, the relationship with her most recent calf may continue for longer.   Overall, while the frequency with which sons and daughters associated with their mother (and/or her group) tends to wax and wane as they get older, they’re generally seen in their mother’s party less often as they approach maturity, although daughters typically associate more closely with their mothers than sons.

Before looking at the stag and hind groups more closely, it is worth considering why we see sexual segregation in this species.   Several theories have been put forward to try and explain these groupings; the two that seem to have amassed the most support are the ‘feeding dichotomy’ (or ‘indirect competition’ hypothesis) and ‘weather sensitivity’ hypotheses.   The first of these, as discussed by Dr Clutton-Brock and his co-authors in their 1982 book, points out that the extent to which stags associate with hinds declines at between three and five-years-old, which corresponds to changes in feeding behaviour, where stags consume more heather while the hinds feed predominantly on grasses.   Why should this be?   After all, rumen content analysis has found that there is little, if any, significant difference between the diets of the stags and hinds during the summer months; why should this change during the winter?   Dr Clutton-Brock and his co-workers suggested that the hinds may out-compete the stags for the short greens (i.e. flushed grassland).   The theory goes that because stags have higher energetic demands, they need more food and, in areas that are heavily used by hinds, the standing crop of the short greens is too low to satisfy their needs and they’re forced on to the heather moorland where the standing crop biomass is higher.   In other words, the heather may be of poorer nutritional value than the grass, but there’s more of it so the stags use less energy trying to get enough of it.   This theory is supported by the observations that the degree of segregation varies according to the plant community the deer have access to and is more pronounced in places where (or during seasons when) food is scarce.   However, more recent data have cast doubt on this hypothesis.

In a paper to the journal Oecologia during 1999, Larissa Conradt, Tim Clutton-Brock and Derek Thomson present their findings on the habitat segregation in Rum’s deer.   The biologists found that even when they reduced the number of hinds on the greens, the males didn’t start using them in favour of the heather, which you’d expect if the females were responsible for the males moving to lower quality feeding sites.   The Jarman-Bell Principle (which states that small grazers are more efficient at grazing short swards and force larger grazers to areas of poorer quality habitat) is well established among mammals, but the authors suggest that the sexual dimorphism between stags and hinds is insufficient for this principle to apply to Red deer – in other words, stags aren’t that much bigger than hinds that the hinds could out-compete the stags for areas of prime grazing.   The authors concluded that:

“the indirect-competition hypothesis does not explain sex differences in habitat use in red deer on Isle of Rum.”

So, if it’s not the female’s grazing ‘technique’ that prevents the stags from using the greens during the winter, what is it?   Dr Conradt and her team don’t propose an alternative explanation in the aforementioned paper, but there is another theory that has gained support.

In 1973, as part of a Master of Philosophy degree at the University of Edinburgh, Anne Jackes studied the use of wintering grounds by Red deer in Ross-shire, Scotland.   Ms Jackes observed that adult stags appeared to opt for shelter over food; they sacrificed the better quality foraging grounds (which tended to be more exposed to the elements) for areas of lower quality food but better shelter – this is known as the “weather sensitivity hypothesis”.   A few years later Brian Staines found that wind direction, and more importantly wind chill, affected the distribution of the deer at Glen Dye in North-east Scotland.   Dr Staines observed that some, more exposed, feeding sites were used less during bad weather, with deer opting to graze in more sheltered areas even though the food may be of better quality on the exposed patches.   Thus, on windy days, it seems probable that the deer’s choice of feeding sites is more limited than it is during calm weather.   More recently, Drs Conradt, Clutton-Brock and Guinness set out to test the weather sensitivity hypothesis as an explanation for the sexual segregation of deer on Rum.   Dr Conradt and her colleagues conducted regular censuses of the deer on the North Block of Rum between 1974 and 1993 and found that while both hinds and stags reduced their use of high quality, but exposed, habitats during bad weather, males were more sensitive to strong winds and low temperatures than females and fed more at sheltered sites on windy days than hinds.   Writing in their paper to the journal Animal Behaviour in 2000, the biologists concede that there probably isn’t a single, universally acceptable explanation to explain sexual segregation among ungulates:

“… it is unlikely that a single explanation applies to the widespread phenomenon of intersexual habitat segregation, and different explanations will have to be sought for different species under different ecological conditions.”

So, the jury is still out as to why the sexes split up during the winter, but it seems likely that, on Rum at least, the stag’s greater sensitivity to adverse weather conditions may be a major factor.   We may not yet see the full picture of sexual segregation, but the question of why deer group in the first place is more straightforward to answer, and there are two primary theories.   Grouping may represent an anti-predator mechanism and the RDRG biologists note that deer in small groups are ‘jumpier’ than those feeding in larger groups – large groups have more eyes to spot a potential predator and more bodies that a predator could choose, meaning the odds of it being you is reduced as group size increases.   Deer may also group as a response to biting flies for a similar reason: more deer means fewer flies per animal.   Deer biologists tend to argue that relief from biting flies is unlikely to be the main reason for deer grouping together, but it is interesting to note that, on Rum, group size shows a tendency to increase on days when biting fly activity is high.   Whatever the reason(s) for grouping, it is a common feature among this species throughout much of its range.   The number of animals seen in groups depends on the habitat (smaller groups form where resources are patchily distributed) and weather conditions (small groups seek out sheltered ground during bad weather) – the range is anywhere from four animals to in excess of one hundred.   Most studies suggest that group size tends to increase as the day wears on, with larger groups seen in the late afternoon and evening.   Deer living in ‘closed’ habitats (e.g. forests) typically form smaller groups than those living in ‘open’ areas (e.g. moorland or greens); this is presumably a combination of the distribution of resources (food, water, shelter etc.) and the physical space available for congregations.

Stag Groups
The detailed studies on Rum’s deer population by the RDRG have shown that the relationship between a stag calf and its mother deteriorates rapidly as the summer wears on, such that the calf is typically only seen with its mother about 20% of the time as the rut approaches.   The calf appears to receive more threats from its relatives during its second year and there is a noticeable increase in the calf’s range size in its third year, as it begins associating more with other stags than the hinds it grew up with.   In their 1982 book, Dr Clutton-Brock and his colleagues recall that about 30% of the stags had moved out of their study population by the time they were five-years-old; this was roughly balanced by stags immigrating from other populations such that about 25% of the six- and seven-year-old stags resident in the population were immigrants.   The biologists also point out that although dispersal distances on Rum are generally small (owing to the size of the island), a report for the Red Deer Commission (now the Deer Commission for Scotland) in 1978 found that 70% of stags tagged on the mainland were recovered more than two kilometres from their birth place – the record was one that travelled 22 km (15 miles).

Deer are good swimmers and crossing channels between near shore islands and the mainland doesn’t present a significant barrier to dispersal, although genetic work by biologists at the University of Edinburgh suggest that in some Highland populations sea lochs, mountain slopes, roads and dense forests can be barriers to dispersal – the data indicate that inland lochs, rivers and railways promote dispersal.   Data, from Snillfjord in Norway, have shown that dispersal distance is understandably related to population density, with stags moving more than 10 km (7 mi.) further away from high density populations than low density ones – the average distances were 37 km (25 mi.) and 26 km (17.5 mi.), respectively, with the greatest distance recorded being 147 km (99 mi.).   Red deer can also display quite a turn of speed and, according to Norma Chapman in her 1991 book Deer, one escaped Red stag was clocked by a police radar trap doing 42 mph (68 kmph) down a street in Stalybridge, Cheshire during October 1970.

Whether stags end up dispersing a few kilometres, or several tens or hundreds of kilometres, they begin exploring at about six months.   Work on Rum shows that stag calves are generally tolerated by harem-holding males until they’re about 18 months old, at which point the breeding male will usually chase them out of the group, although they commonly return after the rut and remain with their mother until the following rut.   In their contribution to the Mammals of the British Isles: Handbook, 4^th Edition, Brian Staines, Jochen Langbein and Tim Burkitt mention that stags leave their mothers at between one year (in Plantations) and two years old (on open ground), or are chased away when the rut begins or a new calf is born.   Dr Staines and his co-authors also note that stags may wander widely, failing to settle for several years, when they establish their seasonal ranges and often associate with other stags.   Stag groups typically consist of individuals of the same age, although mixed-age groups have been documented, with old stags generally seen alone.   On Rum, observations suggest that males typically join stag groups in areas close to those used by the hinds, at between two and three years of age.  

There is no evidence that stags preferentially associate with (or indeed even recognise) male siblings and the groups are usually loose (i.e. less stable than those of hinds); the RDRG have documented how stags in these bachelor parties change core areas, leave and join groups regularly.   Indeed, in their 1982 book, Dr Clutton-Brock and his co-authors wrote:

“The membership of stag parties changed from hour to hour as individuals joined or left.  Relationships between parties were relaxed, and we did not observe either aggressive interactions between parties or cases where one party displaced another.”

The authors also note that, among animals more than four-years-old on Rum, the median (i.e. middle) group size of stags in the summer months was seven individuals, declining to groups of four during the winter.   In his 1967 A Field Guide to the Mammals of Britain and Europe, Frederik Hendrik van den Brink notes that old, non-pregnant or infertile hinds are sometimes found in these bachelor groups.   Stag groups have a hierarchical structure that seems more linear than that of hind groups (i.e. there are fewer cases of low-ranking animals dominating higher-ranking ones in stag groups) and dominance relationships seem to be relatively consistent year-on-year.   The factors affecting the placement of an individual in the hierarchy are complicated and poorly understood.

While stags retain their antlers, the ‘pecking order’ -- so named, incidentally, because it was first described in chickens by the Norwegian zoologist Thorleif Schjelderup-Ebbe in 1921 -- is largely based upon body size, although once the stags have cast their antlers this situation changes.   The stags will each lose their antlers at different times associated with their place in the hierarchy – the higher the rank, the earlier they cast, re-grow and clean their antlers.    The reason for this association appears to be related to access to food and studies by Cambridge University zoologist Michael Appleby has shown that higher-ranking stags excluded lower-ranking animals from the experimental feeding plots he setup on Rum.   Dr Appleby suggested that holding a high rank might allow a stag to improve body condition by turfing lower-ranking stags out of prime feeding spots; this ‘displacement’ was more common during the winter when food is at its scarcest; peaking in March, when food was at a minimum.   Given that several studies have linked antler casting dates to the nutritional state of the stag, it is not difficult to see how holding a high rank, and the access to more/better food it conveys, could lead to earlier casting.

Stags will sometimes leave the bachelor group briefly to shed their antlers and, when they return antlerless, they often find themselves at a lower position in the hierarchy.   Studies on Rum by Dr Appleby have shown that, even though the hierarchy starts to re-establish once all the antlers have been cast, the linearity of the hierarchy is disrupted until the antlers have been cleaned.   While the antlers are growing (and are thus in velvet), disputes are settled by rising up on hind legs and kicking out with forefeet – this is referred to as “boxing”.   Observations on captive deer -- which are maintained in mixed-age groups -- have shown that the stags generally don’t remain in the same social group while they’re in velvet, preferring to associate with individuals of a similar age or rank.   Work on the “white red deer” held at Czechoslovakia’s Zehusice Game Reserve by Ludek Bartos and Vaclav Perner has found that the greatest number of stag groups occurred as the cleaning period approached (i.e. there were more, smaller groups), as did the number of solitary stags observed and probably for good reason.   Writing in the journal Behaviour in 1985, Drs Bartos and Perner note:

“Increases in the size of a social group caused increased levels of aggression in dominant stags and increased the number of attacks on subordinate stags.”

Once the antlers have been cleaned, by late summer, the stags may engage in sparring matches, which should not be mistaken for dominance challenges.   Among the stags, the RDRG biologists observed that displacements -- where one animal walked steadily, in a ‘stiff gait’ towards another, forcing it out of the feeding site -- were the most common threat displays, while dominant stags were also observed to raise their head back (pointing the chin at their opponent), curl their lip up and hiss or grind their teeth.   Failure of the opposing stag to back down was met with a nod or shake of the head (I have observed Sika stags, Cervus nippon, to do a similar thing at bystanders or photographers that venture too close), a jab with the antlers or a kick, which if performed with both front legs simultaneously is often referred to as a ‘scissor kick’.   Apparently, biting is rare.   The opponent is typically chased away from the immediate area or feeding site, but seldom driven out of the locality.   In their 1982 book, the Cambridge University biologists report that although the ‘threat rate’ increases during the winter for both sexes, in a discovery that won’t surprise most of my female readership, males threatened each other about three-times as frequently as hinds threatened each other.

In autumn the bachelor groups break down and the stags disperse to the rutting stands – there is, incidentally, some evidence to suggest that males holding high ranks in bachelor groups tend to be more successful in the rut and sire more offspring, which is perhaps not a surprise given the increased food benefit that being high in the pecking order seems to convey.   Once the rut is over, by late November or early December, the groups reform.   Writing in his 1980 paper to the journal Behaviour, Michael Appleby noted that:

“… after the rut, reformation of the group involved fighting in some dyads [pairs of stags], but the hierarchy was then stable again through the winter.”       (Back to Menu)

Hind Groups
Female groups seem more stable than bachelor groups – when the RDRG performed a statistical test called cluster analysis (which, as the name implies, looks at the arrangement of natural groups), they found that the majority of the clusters were small (four, or fewer, animals), matrilineal -- consisting of genetically related hinds -- and stable in composition (i.e. didn’t change year-to-year).   In their 1982 book, Dr Clutton-Brock and his co-workers discuss the findings of the cluster analysis study and point out that the core areas of the hind groups overlapped extensively, but rarely coincided perfectly with each other.   Overall, the biologists observed that the median hind party size on Rum was seven individuals in summer and five during the winter.   As mentioned above, male calves of up to two years old may also join the group.

Hind groups are typically both matriarchal and matrilineal in nature, meaning that they have a hierarchy where a mother is dominant to her daughters and each daughter is dominant to another, younger, daughter.   In hinds older than three years dominance rank appears to be related to age (i.e. younger hinds are subordinate to older ones).   Interestingly, dominance relationships appear stable even as the animals change through the years.   In a paper to the journal Animal Behaviour during 1990 Chris Thouless reports that dominance relationships established early in life remained even though the hinds changed in body size as they grew older.   This might explain why hinds are generally reluctant to leave their group, even if they currently hold a low ranking; hinds who know each other don’t have to undertake risky contests to establish dominance, while if they moved to a new group, they’d risk potentially dangerous conflict trying to establish their place, which might be as low or lower, in the ‘pecking order’.

On Rum, the RDRG biologists have observed that daughters tend to associate less with their mother as they grow older and, by the time they reach four or five years old, they adopt their own range that often overlaps with their mother’s range.   In their 1982 book, the Cambridge University researchers note that, on average, hinds more than three years old shared about 30% of their core areas with their mothers.   Interestingly, the research on Rum has shown that the daughters of young mothers tend to associate more closely with the dam than do daughters of older mothers – it has been suggested that this may reflect that older hinds generally have more daughters than younger ones and the calf seeks companions of her sisters rather than her mother.   Concomitantly, sisters are commonly seen in groups with aunts and nieces.   Dr Clutton-Brock and his colleagues sum up nicely the phenomenon of hind groups in their 1982 book, in which they write:

“Hinds tend to associate with their mothers and sisters more frequently than with animals that do not belong to the same matriline.”

Why should this be so?   Why do animals associate more with their relatives than strangers?   Well, generally among social animals, we see that relatives tend to be more tolerant of their own offspring than those of strangers and will allow family members to feed closer to them than they would a stranger (this may also be sex dependent; on Rum it has been shown that hinds tolerate other hinds at closer proximity than stags tolerate other stags).   Similarly, it is now well-established for a number of species now that a youngster is safer from predation or attack when near its parents or another family member, who are considerably more likely to intervene than a stranger.   I don’t want to go into too much detail about this, but the idea that by protecting your close relatives you’re also protecting, and thus aiding the survival of, some of your own genes is known as the ‘selfish gene theory’.   I would direct any interested readers to the fascinating book, The Selfish Gene, by evolutionary biologist Richard Dawkins; Professor Dawkins explains the idea far better than I could hope to.   It certainly seems that it is beneficial for a deer to associate with its relatives and observations from Rum have documented that orphans that aren’t adopted early in life are often subjected to aggression from the herd and typically hold a low status in the hierarchy.

One might be tempted to think that life in a hind group might be more ‘relaxed’ than a stag group, but this doesn’t appear to be the case.   We’ve already seen that stags fight with each other more often than hinds squabble, but hinds can still be aggressive.   On Rum, matrilineal threats (where a hind threatens a close relative) were found to be less common than threats made to strangers and in their study of one population between 1977 and 1978, the RDRG observed that hinds between three and six years old received about seven matrilineal threats and 129 non-matrilineal threats (i.e. threats from strangers).   It appears that not only were matrilineal threats less common than other threats, they were also less intensive/aggressive.   The most common threats were ‘nose and ear threats’, which involved jabbing the nose at the neck of another animal while exhaling loudly, and flattening the ears on the head while walking towards another animal, respectively.   Hinds also kicked, bit and chased other hinds, generally in a bid to remove them from the immediate vicinity (presumably to have the feeding site to themselves), rather than drive them out of the area.   Disputes were also settled by boxing, in the same way that antlerless or velvet stags were observed to fight.   In their book, Dr Clutton-Brock and his colleagues note that despite their appearance, the threats from hinds could lead to lasting injuries:

 “Adult hinds not infrequently show the marks of kicks or bites on their flanks and ears, and a significant proportion of hinds shot in the annual cull had broken ribs.”

A study of the 560-or-so deer of the Val Trupchun valley in the Swiss National Park during 2003 yielded similar results to those presented for Rum.   The data, collected by Nicole Bebie at the Universitat Zurich in Switzerland and Alan McElligott at the University of London, was published in the journal Mammalian Biology during 2008 and show that displacements, nose threats and kicking were the most common forms of aggression, with biting, ear threats and chases recorded less frequently.   The zoologists also found that of the three social situations they studied -- i.e. females in oestrous and in a harem; hinds in a feeding group; and non-oestrous hinds in a harem -- the first two exhibited significantly more aggressive interactions than the third.   Interestingly though, the scientists didn’t observe any relationship with aggression levels and group size – ordinarily, one would expect that there would be more aggression in larger groups, but this doesn’t appear to be the case for these Swiss deer.   Drs Bebie and McElligott suggest that higher aggression in oestrous females might represent evidence of female competition for mates and that increased aggression in feeding groups could reflect a mixing of unrelated animals feeding together (while harems tend to be composed of related individuals).   The latter of these seems to be supported by observations that family groups may merge in open areas while feeding, splitting up again upon returning to cover.   Data from Rum add support for the initial conclusion of Drs Bebie and McElligott and in their 1971 paper to the Journal of Reproduction and Fertility, Fiona Guinness, Gerald Lincoln and Roger Short note that:

“A hind’s position in the social hierarchy did not change at oestrus, but some became much more aggressive towards subordinates and demonstrative towards humans.”

Despite the above, some studies suggest that aggressive encounters are generally low among the hinds and, in his 1990 Animal Behaviour paper Chris Thouless notes that feeding competition among hinds was generally passive – that is, subordinates generally avoided dominant individuals, moving away if one approached.   Indeed, Dr Thouless found that the feeding rate, as measured by the number of bites of food taken, of a subordinate increased the further she was from dominant hinds, but was unaffected by how close she was to individuals of the same, or lower, rank.

In many mammalian societies, social bonds are reinforced by grooming.   The rate of grooming between hinds of the same social group appears fairly low, although the RDRG document occasional observations of hinds grooming other hinds (always family members); licking and nibbling around the face, head, neck and ears.   Grooming among stags is apparently extremely rare and although hinds have occasionally been seen to groom adult stags (i.e. those over two years old), this seems to be generally confined to the rut.  (Back to Menu)

Communication
So, we’ve seen that deer are highly social mammals, forming mixed and single-sex groups depending upon the season; but how do the deer communicate with each other?   Well, much of the communication between deer is scent-orientated.   In her 1991 book Deer, Norma Chapman notes that among the Cervidae (deer family) as a whole there are at least 13 sites on the body where a scent gland is known to be situated; although no single species is known to have all 13 glands, most have a combination of them, some of which are active all year around and others that are only active during certain seasons.   The secretions of these glands come from specialised sweat and sebaceous glands within the skin, the latter of which produce fatty compounds – some of these secretions, as is the case for the tail gland of Red deer, take the form of a tar-like substance.   Red deer possess several of these skin glands that include those on their ankle or ‘hock’ (metatarsal glands), those on the inside of their back legs (tarsal glands), those between the cleaves of the hooves (interdigital glands), those on the underside of the tail (subcaudal gland); and that just in-front of the eye (the lachrymal, or pre-orbital, gland).   In general, the scent produced by these glands may encode messages about the age and sex of the animal, and each deer may have its own distinct scent.   The histology of the glands and the chemistry of their contents are outside the scope of this article, but I will try and summarise the basics.

Gerald Lincoln has demonstrated that the subcaudal and lachrymal glands of Red deer increase in size and activity during the rutting season, which ties in nicely with behavioural observations of stags in the wild that document them opening their lachrymal glands while roaring, parallel walking and fighting.   Work by University of Trondheim (in Norway) researchers Jan Bakke and Erik Figenschou has uncovered details of the chemistry of some gland secretions as well as the urine chemistry – urine is often sprayed into wallows and scrapes as well as being released during rutting clashes.   In a paper to the journal of Comparative Biochemistry and Physiology during 1990, Drs Bakke and Figenschou documented 70 volatile compounds from Red deer urine, the majority being carboxylic acids or their derivatives.   It seems that, during the rutting season, the amounts of these compounds in the stag’s urine increase significantly, alluding to a change in the animal’s metabolism.   In an earlier paper, to the Journal of Chemical Ecology, the same authors identified nine volatile components from the subcaudal gland of Red deer.   In chemical terms, the more volatile a substance is the more prone it is to vaporizing and thus the better it is as a candidate for being odiforous.   The components of the gland secretion can change according to season and the age of the animal.   Work by deer biologists Ruth Lawson, Rory Putman and Alan Fielding has shown that the lachrymal secretion of Red deer changes as the animal ages and, in their 2001 paper to the Journal of Zoology, suggested that some of the secretions from deer scent glands may carry “coded information about sex and possibly age as well as for the individual identity of the signaller”.

Scent is also an important component of mother-offspring communication and the pre-orbital gland seems to play a particularly important role.   The pre-orbital gland sits in a depression, or tear-pit, just in front of each eye and is covered by a flap of skin under nervous control so the deer can open and close it.   The scent gland produces a strong-smelling waxy substance that’s usually yellow in colour.   Some authors have suggested that the hind soon learns to distinguish the scent of her calf, even from some distance away, and if danger threatens, the calf will crouch down and close its scent gland – the hind can detect the cessation in scent from her calf, and will quickly return to it.   Off-hand, this seems an odd strategy, because if a dam can detect the scent from a distance, surely the keen nose of a predator could too?   Thus, it seems to make more sense that the gland should be opened to start an odour trail and alert the dam to a problem; new research suggests this may indeed be the case.

Studies by biologists at the Research Institute of Animal Production in the Czech Republic suggest that it is actually the opening of the pit that signifies stress and calves in their relaxed state typically have their glands closed.   The scientists observed that when calves were manipulated by researchers (to mark them with an ear tag) all the animals opened their pre-orbital pit, whereas before they were caught (while they were lying in their enclosure), all but three calves had their glands closed.   Previous studies by the same biologists have suggested that there are various other factors that affect whether the pre-orbital gland is open or closed, including whether they’re hungry or excited.   Observations on the calves while suckling revealed that some (although not all) opened their glands when hungry and closed them when they’d drunk their fill.

Sound is also important in Red deer society.   Red stags are fairly quiet outside of the rut, but during the breeding season they may spend much of their time roaring – the stags produce a deep, loud, resonating roar/bellow, which is sometimes called “balving”, especially in parts of southwest England (see Q/A).   Stags may also bark when alarmed, while hinds produce a sharp bark or high-pitched squeal when alarmed and may also produce a growling sound when anxious.   Both sexes are known to produce low grunts when approaching each other.   I have already mentioned John Fletcher’s observation that hinds, under the influence of oestrogen close to parturition, can bellow like stags and there is at least one record to suggest they may do the same when scared or stressed.   In a fascinating short communication to the Journal of Zoology in 1969, A. B. Cooper described an attack on a Red deer calf by a Golden eagle (Aquila chrysaetus) that he witnessed in July of the previous year.   Mr Cooper wrote of how the “howl” that the calf had given upon being struck by the bird had alerted a group of deer over the other side of the hill; these deer (a party of nine hinds) started to “low and bleat in an anxious manner” as they came looking for the calf.   Mr Cooper then wrote:

“The nine hinds kept up a constant lowing, similar to the bellowing of stags, and frequently gave the reedy bleats characteristic of milk hinds.”

Once the eagle had flown away, the hinds lowed for a few minutes before quieting down.   Calves, when not being ambushed by a large bird of prey, tend to emit a softer ‘bleat’, which the hind responds to with a louder nasal bleat, not dissimilar to that produced by sheep.   In their Mammals of the British Isles: Handbook, 4^th Edition, Brian Staines, Jochen Langbein and Tim Burkitt describe a “low mooing” that the hinds make when locating their calf.

In terms of other behaviour, Red deer stags may also partake in mud wallowing – a favoured wallowing hole will generally be scraped with the feet and sprayed with urine before the stag commences wallowing.   The wallowing pits are generally two or three metres in diameter and emanate a strong musky smell.   The heavily scented mud is then spread over the stag’s body.   Hinds are also known to wallow, although apparently less often than stags, and stags have been seen wallowing outside of the rutting period.   Wallowing behaviour often coincides with the moult and the mud may help remove loose hair; it may also help provide relief from biting insects.

Tail-flagging, where a deer erects its conspicuous white tail when fleeing from a disturbance, is well documented in Red deer; it has been suggested to signal to a predator that the deer has spotted it and it has thus lost the element of surprise, and attack is therefore futile.   Some authors have documented the deer to flare their rump and ‘pronk’ away.  (Back to Menu)

Interaction with Humans: Historically, Red deer were considered a ‘beast of chase’ by the Norman kings, who set aside large areas of their kingdoms so they could hunt stags – the deer, and other hunt-worthy animals were protected by stringent forest laws and poaching of the king’s deer was met with often brutal punishment.   Today, stag hunting is generally carried out only by stalkers under licence; the Hunting Act of 2004 made it illegal to chase deer on horseback with staghounds.   Despite the best efforts of deer stalkers, it seems that the current mortality of Red deer in the UK is insufficient to offset population growth and deer numbers are estimated to be higher now than they have been at any point in the last five decades.   Consequently, there is concern for potential conflict between deer and landowners for space and, at the local scale at least, deer can be serious predators of cereal crops and can cause considerable damage to plantations.

Numbers and Management
The available fossil data suggest that Red deer appeared during Europe’s mid-Pleistocene Cromerian Interglacial period (about 400,000 years ago), having probably evolved from the Sika-like Cervus perrieri, where they are the earliest deer associated with woodlands.   It appears that Cervus elaphus died out throughout much (if not all) of Europe during the Younger Dryas cold spell, returning (and extending their range to Great Britain) during the early Postglacial period.   Indeed, Red deer were once plentiful in Britain, where they were hunted by our early ancestors for skins and meat, but this species has endured something of a tumultuous history in the UK; there is even some evidence to suggest that early man farmed deer for their antlers, which were carved into tools and jewellery.   For a comprehensive and enlightening account of Red deer history in Britain, the reader is directed to Derek Yalden’s seminal 2002 book, The History of British Mammals.   In summary, we have a good record of Red deer in Britain dating back to the end of the Anglian Glaciation, some 300,000 years ago, in remains from Hoxne in Suffolk.   Remains dating back to the Wolstonian Glaciation of Jersey suggest that human hunters were taking Red deer as prey around 150,000 years ago.   Interestingly, archaeological evidence suggests that the Red deer present around the time of the Devesian Glaciation (which ended about 12,000 years ago) were considerably larger than modern day animals, rivalling the Canadian wapiti at about 400 kg (880 lbs. or 63 stone) and with basal antler circumferences of almost 30 cm (12 in.), compared to the 120 kg (265 lbs. or 19 st.) and 20 cm (8 in.) of today’s Scottish hillside stags!   We also have remains from Somerset that date to between 12,800 and 11,900 years ago, putting Red deer among the late glacial mammals of Britain (hence their status as native animals).   In Ireland, Dr Yalden notes that carbon 14 (radioactive) dating of remains found at County Waterford, part of the province of Munster in the south of the country, suggests that Red deer were present around 26,000 years ago and possibly as long ago as 39,000 years ago (mid-Devensian Glaciation).   The influence of Red deer on early settlers can be seen in the research of Sarah Beswick; her investigation, recounted by Dr Yalden, has turned up at least 185 place names making reference to Red deer, including Hartwell in both Aylesbury and Northamptonshire, and Hindhead in Surrey.

Red deer seem to have survived well following the retreat of the ice at the end of the last (Devensian) Glaciation, when Britain was a largely tree-covered island.   Growing pressures for land led to clearing of woodland and by the end of the 18^th Century, few stands remained in the Scottish Mountains.   The breakdown of the Scottish clan system lead to the immensely unpopular Highland Clearances of the late 1700s and early 1800s, during which landlords evicted people from their homes in the glens and imported considerable numbers of blackface sheep, which added to the grazing pressure already applied by the deer.   Eventually, the sheep and their shepherds were translocated to New Zealand and there was a substantial decline in Scottish hill sheep farming.   Elsewhere in Britain, Red deer started declining in England during the Middle Ages owing to an increased need for timber and an increased demand for hunting the introduced Fallow deer (Dama dama).   At this point, nobility began establishing areas of forest as hunting grounds for the sport of the King or setting up deer farms to provide venison to royalty.   In 1079 William the Conqueror declared an area of Hampshire, the Nova Foresta (or New Forest), a royal hunting preserve in which only he was permitted to hunt.   Deer gradually became more of a fashion accessory and no grand estate was complete without deer roaming the grounds.   As the Crown began to lose interest in deer, the forests were progressively felled and sold off to private owners or divided up by Enclosure Acts.   Queen Elizabeth I renewed some interest in the forests as a source of deer (leading to an increase in Red deer by 1586), and some of the Stuart monarchy maintained an interest in hunting.  

Unfortunately, deer became such a problem for forestry that some areas implemented legislation to remove them as a ‘pest’ species.   In the New Forest, the Deer Removal Act was passed in 1851 -- ironically the same year that Sir Edward Landseer was commissioned to paint the iconic Monarch of the Glen -- because, as Terry Heathcote puts it in his book A Wild Heritage:

“From the viewpoint of the Crown [the deer’s] usefulness had now passed, but worse they were costing the Crown money because of the damage they caused.  Even the commoners did not want them because of the competition with their stock for available grazing on the open forest.”

The result of this Act was that deer (of all species) numbers in the Forest crashed and remained low for much of the following 50 years.   The money that had been allocated to the deer extermination, however, eventually ran out and this lead to deer numbers starting to increase again from the early-1900s.   Fallow deer were the most numerous deer species in the Forest when the Act was passed and suffered the most substantial decline; historical data on how this affected the Red deer is sparse and it is difficult to assess what impact the Act had on their numbers.   Colin Tubbs, a passionate naturalist and legend of the New Forest, picks up the story in his classic reference work, The New Forest (originally published in 1986 and revised, by his widow, in 2002), in which he wrote:

“The red deer population has been small for at least 400 years and has been sustained by periodic introductions.”

Prior to the passing of the Hunting Act 2004, stag hunting was a fairly popular sport in the UK.   In 1997 University of Cambridge physiologist Professor Patrick Bateson presented a controversial report to the British government suggesting that deer suffer unnecessarily from being hunted with hounds.   While vehemently supported by most animal welfare groups, it is not a surprise that the data have been questioned by the pro-hunting lobby and that a subsequent report, commissioned by the Countryside Alliance and published in 1999, presented data suggesting that hunting was less stressful on stags than Prof. Bateson’s conclusions indicated.   Interestingly, if you read the reports you find that the data are actually fairly similar, but the authors draw opposing conclusions from it.   The situation is far from clear, but anyone wishing to find out more is directed to Richard North’s excellent overview The Hunt At Bay: A Paper on Stag-Hunting.

Today, in many areas of the country, deer numbers are carefully managed by the Forestry Commission who pay stalkers to harvest them; the population of Cervus elaphus in the New Forest, for example, is maintained at between 80 and 200 animals.   Overall, however, while control can be effectively managed at a local scale, there is no single body in the UK that is responsible for coordinating deer control.   The Deer Commission Scotland is the lead agency in Scotland as set out under the Deer (Scotland) Act of 1997; the DCS is funded by the Scottish government and advises on the protection of agriculture, forestry and other natural heritage and welfare management issues.   The closest comparable body in England is probably the Deer Initiative, which is a charitable partnership of 21 wildlife and farming groups that is responsible for some deer policy decisions.   Unlike the Deer Commission in Scotland, the Deer Initiative cannot force landowners to control deer numbers on their land, although they do interface with Natural England (a non-departmental public body of the UK government), who can intervene if necessary.   The British Deer Society, which was established (i.e. broke away from the Mammal Society) in 1963 in response to a growing need to control of deer in Britain following World War II, is another charity that advises regulatory and private bodies on subjects relating to deer management and welfare.   In Northern Ireland, deer control falls under the jurisdiction of the National Parks and Wildlife Service.

The Deer Initiative has estimated that we should be culling around half-a-million deer (around 25% of the estimated population) each year if we are to maintain populations at manageable levels – it is unclear precisely how many Red deer should be culled, but in an interview with the BBC during 2005, BDS technical officer Hugh Rose, suggested that 30% of the population (about 120,000 animals) should be culled annually.   Unfortunately, there is currently a lack of full-time deer stalkers in the UK and, as a consequence, about 350,000 deer (of all species) are currently culled annually.   In a recent investigation for the BBC current affairs series Countryfile, it was estimated that some 90% of stalkers shoot as a hobby, which leaves the door open to private trophy hunters and this can lead to a shifting of selective pressures.   If we take the Highlands of Scotland as an example, it costs around £350 (about US$ 550 or €400) to shoot a stag on an organised stalk and, in a 1992 paper to the journal Nature, Tim Clutton-Brock and Steve Albon estimated that the majority of the 16,000 stags killed each year in the Highlands were shot by tenants and clients of stalking estates.   The problem is two-fold.   First there is a distinct preference for shooting stags, which make the better trophies, but this means that hinds aren’t as popular and are either left to breed or killed, often at a loss, by estate employees. Secondly big stags, with impressive antler sets, are generally more appealing to hunters than smaller ones.   With more hinds around, there is a tendency for poorer growth of males (because, as we have seen, they deplete their resources more quickly than hinds) and where large males are preferentially culled there is a selective pressure towards smaller males with smaller antlers – in other words, if all the large, fit and strong males are shot, it’s the smaller ones that survive to pass on their genes and this generally isn’t seen as good for the population.   Thus, in order to maintain a healthy Red deer population there should be a properly targeted cull of stags, hinds and calves.   In England and Wales, the open season (i.e. period when deer can be shot) runs from 1^st August until 30^th April and 1^st November until 28^th February for stags and hinds, respectively.   In Scotland stags can be shot between 1^st July and 20^th October, while the hind open season runs from 21^st October to 15^th February.

The prospect of a cull is an uneasy one for some communities, and not without its controversy; especially where Red deer are relied upon as a source of tourism.   In 2004, more than 100 gamekeepers from 60 estates converged on Glenfeshie Estate, in Strathspey (Scotland) to protest about Scottish Natural Heritage’s plans to carry out a cull of the Red deer that these keepers point out is their livelihood.   This is perhaps not a surprise when one considers that, according to the British Association for Shooting and Conservation Scotland, the deer stalking industry is worth an estimated £240 million (US$ 377 million or €276 million) to the Scottish economy, and supports the equivalent of 11,000 full-time jobs.  The Parliamentary Office for Science and Technology are rather more conservative in their estimates and, in their 2009 POSTnote, they reference the findings of a 2006 report by the Public and Corporate Economic Consultants, stating:

“In Scotland, sustaining wild deer for sport is a primary management objective across much of the Highlands, and is estimated to contribute over £170 million to the economy.  Deer management provides the equivalent of over 2,500 full-time jobs in Scotland…”

It should be mentioned briefly that immunocontraception is currently being tested as a method of population control for deer in America.   I don’t want to cover it in any detail here because it is not currently being tested on UK deer, but the basic premise is that you can use the deer’s immune system to prevent fertilization if you inject females with a Porcine zona pellucida vaccine (extracted from pig ovaries and commonly abbreviated to PZP).   The zona pellucida (meaning roughly ‘transparent belt’ in Latin) is the transparent membrane that surrounds the mammalian egg and contains receptors to which spermatozoa bind, resulting in fertilization.   Injection with PZP causes antibodies to form on the deer’s zona pellucida, blocking sperm from attaching to the egg and thus inhibiting fertilization.   Despite some argument from the pro-hunting lobby, some confusion in the media over the difference between sterilization and immunocontraception (the latter being wholly reversible infertility), and some unfounded concerns about the impact on the food chain, the results are positive.   Biologists working with White-tailed deer (Odocoileus virginianus) on the National Institute of Standards and Technology campus in Gaithersburg (Maryland, USA) have found that they were able to reduce the population by an average of 8% per year by injecting the females with PZP vaccine.   Nonetheless, while immunocontraception is being trialled in parts of the USA, there are (to the best of my knowledge) no such trials underway in the UK and culls by stalkers are the primary method of controlling populations.

So, why is a cull necessary?   What is the problem with having lots of deer?   Well, increasing deer numbers puts increased pressure on resources and deer can come into conflict with landowners (by eating and trampling crops and competing with livestock for food) and forestry.   In an assessment of Red deer stock in the Highlands of Scotland, published in Nature during 2004, RDRG biologists wrote:

“Grazing by hill sheep and red deer prevents the regeneration of woodland in many parts of the Scottish highlands and has also led to extensive loss of heather cover.”

Indeed, Red deer can pose a considerable problem for forestry, especially commercial conifer plantations.   Damage from deer can be split roughly into that resulting from direct consumption (‘feeding damage’) and that arising through more indirect actions (‘non-feeding damage’).   Deer will nibble on new growth, especially leading shoots and runners of saplings, which can retard development at sufficient intensity (moderate grazing can serve to stimulate new growth and increase yield).   Deer will also strip bark -- trees are stripped upwards because deer use the teeth in their lower jaw -- which can be included under the feeding category because the bark may or may not be eaten; in periods of harsh weather, bark may account for some 10% of the diet.   The feeding actions of Red deer can result in a ‘browse line’ -- lower branches are stripped clean of leaves and buds to a consistent height -- extending to a height of just under two metres (6ft) above the ground.   Indirect, or non-feeding, damage comes from trampling and fraying – during the rutting season, Red stags will fray vegetation as a means to remove velvet from their antlers and may rub against trees to remove loose hair during the moult.   The stags generally fray tree saplings that are 10 cm (4 in.), or less, in diameter – the damage is generally confined to a height of less than 1 ½ m (5 ft) from the ground.

Deer grazing can prevent tree seedlings from growing, which is beneficial if the management aim is to maintain open grassland, but not if the desire is for woodland regeneration.   Additionally, a penchant for browsing back undergrowth has also resulted in deer being implicated in the decline of ground-nesting bird species.   There isn’t much evidence implicating Red deer specifically, but it seems that an overabundance of deer in general can lead to a decrease in songbird habitat quality through both decreased food resources and a decline in nest site quality and shelter.  

In terms of agriculture, deer can also make a nuisance of themselves, although the significance of the damage varies locally.   Red deer are generally associated with damage to cereal and root crops, which they either eat or trample; they rarely occur in gardens and thus aren’t a significant problem to horticulture (compared with Roe deer).   Radio-tracking studies of the Red deer on Exmoor have shown that they can make extensive use of ‘improve pastures’ (those fertilized for use by livestock), especially during the night when some 25% and 35% of radio-fixes found hinds and stags, respectively, on these pastures.   A similar tracking study on a Red deer hind from Ashtead Common in London revealed that, depending on the season, between 45% and 60% of GPS fixes found her on agricultural land (bear in mind this may not be representative, given that only a single hind was collared).   The authors of the study, conducted with funding from DEFRA, suggest that the hind may have been targeting what farmers refer to as the ‘early bite’, that is, the start of the growing season when grass is at its most nutritious.   The aspect that really ‘jumps out’ when you read these studies is that there is considerable variation both with season and with locality and it is difficult not only measuring deer damage, but also predicting it.   Moreover, many of these studies are several years old now, as are the financial estimates of deer crop damage (one 2003 estimate for Red deer damage to wheat crops in Eastern England was £60 per hectare).   Nonetheless, it has been estimated that Red deer damage to crops is more likely where densities are greater than about one animal per four square kilometres (1 ½ miles).

I don’t wish to pursue these topics further here, because they are covered in greater depth in the main deer article and associated Q/As.   Overall, however, it has now been well established that Red deer can have a major impact on forestry and some native woodland plants and cereal crops, and there is certainly the potential for their grazing activity to affect some woodland bird species.   There is also some, admittedly rather circumstantial, evidence to suggest competition between deer species – it seems that Fallow deer in parks often do worse when there is a large population of Red deer present.

A second problem associated with high population numbers is the impact on the health of the deer.   As numbers rise, competition for food and space increases and each deer is typically in poorer condition than when populations are low.   A consequence of poor condition is that the animal is more susceptible to disease than it is when healthy and, at high density, such susceptible animals are usually closer together and so diseases can spread more easily through the population.   Some deer diseases are zoonotic in nature, meaning that they can be transferred to humans, while others can affect livestock.  (Back to Menu)

Parasites and Diseases
Lice and ticks are probably the most common ectoparasites (ecto- from the Greek ektos, meaning ‘outside’ or ‘external’) and the deer tick Ixodes ricinus (see left), which can carry the Lyme Disease bacterium Borrelia, is probably the most common of these.   Lyme Disease is transferrable to humans, although it seems that the ticks are generally picked up by walkers from vegetation rather than via any direct contact with the deer themselves.   Tiny crab-like insects called deer keds (Lipotena cervi) feed on skin and blood, while sucking lice (Solenopotes burmeisteri) and various biting lice species are also fairly common.   These parasites are rarely more than an irritant to the deer.   There are, however, some that can potentially do more damage.   A significant parasite of Red deer is the Warble fly (Hypoderma diani), which is most problematic during the spring when a single deer may be infested with more than a hundred larvae.   The adult fly lands on the deer and pierces its hide to lay its eggs under the skin.   The larvae of the fly don’t burrow into the deer’s flesh, but remain under the skin – as the larvae develop they form lumps (called ‘warbles’) under the skin which remain through the winter until the maggots drop from the deer’s back in early spring the following year.   The condition isn’t generally fatal as the lumps will heal once the larvae have hatched, although the open sores can sometimes become infected.   Another significant parasite of Red deer is the nasal-bot fly (Cephenemyia species), which lays eggs in the nose of the deer; the eggs develop into maggots roughly three centimetres (one inch) long with well developed bristles that allow them to cling to the base of the nostril.   The maggots can then migrate up the nostril to over-winter, feeding on blood and mucus, before crawling back down and dropping out in the spring – the maggot typically cause the deer irritation (causing considerable coughing and sneezing), but in sufficient numbers they can block the nasal passages and suffocate the deer.

Deer can also suffer from a range of endoparasites (endo- from the Greek endon meaning ‘within’ or ‘internal’) including the tissue worm Elaphostrongylus cervi, lungworms of the genus Dictylocaulus (these are of considerable concern to the deer farming industry and can heavily infest malnourished wild calves causing appreciable mortality), liverflukes (Fasciola hepatica) and various tapeworms.   As with the ectoparasites, these endoparasites generally don’t lead to the death of their host, but under conditions of hardship when the deer is undernourished, they may represent an additional drain that can prove fatal.   There are several viruses and bacterial infections that have been documented in deer -- including rhinotracheitis, bovine herposvirus, Mycobacterium (including M. bovis and M. avium) and Salmonella -- but they are rare and cases of clinical infection are exceptional.   The Mycobacterium bacteria have been in the headlines for some time now over their ability to cause tuberculosis; most of the attention has focused on M. bovis, which causes bovine tuberculosis (bTB) - see Q/A.  

The nervous system disorder Chronic Wasting Disease (CWD) is well known from deer and further details can be found in the Q/A.   Tumours occur very rarely, as do cases of infection with the protozoan parasites Babesia and Toxoplasma, some species of which can be passed to humans.   There are no records of bovine spongiform encephalopathy (better known as BSE) in wild deer, although laboratory studies have shown that they are susceptible to it – thus far, symptoms (which include anorexia, blindness, ‘panic attacks’ and failure to moult) have only been induced by direct injection of infected material into the deer’s brain.   In addition, farmed deer have died as a result of vitamin deficiency.   During the late autumn of 1999 three adult hinds in a Norwegian deer park died shortly after presenting as ‘generally thin and unthrifty animals’ with very dull light-coloured hair and diarrhoea.   A necropsy was carried out on the animals and it revealed that all three were suffering from copper and selenium deficiencies.   The biologists who conducted the post mortems tried an experiment, the results of which were published in the journal Acta Veterinaria Scandinavia during 2008.   The scientists found that just giving the deer a copper-enriched salt lick in their enclosure wasn’t sufficient to maintain their copper requirement and they had to give the animals copper oxide capsules every couple of months to maintain their condition.   When copper levels returned to normal, the deer’s coat condition dramatically improved, as did their overall body condition; the biologists also observed increased fertility and reduced parasite load.

Much of our understanding of deer diseases, indeed of deer biology in general, has come from studies conducted on deer in parks, farms and in nature reserves and there are some diseases that have caused appreciable mortality to captive herds.   Malignant Catarrhal Fever, a fatal viral infection caused by the Ovine herpesvirus-2, presents with symptoms of blood-shot eyes and blood and foaming around the mouth following an incubation period that can last from six weeks to five months; it has led to high mortality of Red deer in New Zealand deer farms.  (Back to Menu)

Deer Parks & Farms
In his book, A Life for Deer, John Fletcher tells of how the Victorians sent crate-loads of Red deer from English deer parks up to Scotland by train in a bid to re-stock the Highlands and improve the quality of the stock – this apparently continued up until the start of World War II.   Dr Fletcher amusingly describes attempts to improve the Highland deer quality by introducing different subspecies as ‘rather misguided’, pointing out that “undoubtedly the limiting factor in the productivity of Highland red deer is very rarely the genetics of the deer but rather the environment: food and shelter”.   It was actually during the Victorian period that the foundations were laid for one of the longest studies on a wild mammal population conducted anywhere in the world.   According to Dr Fletcher, the (second) Marquis of Salisbury bought the island of Rum in 1845 (for £26,455), with the apparent goal of making it a hunting estate – he reintroduced Red deer to the island and tried, in vain, to establish a population of Fallow.   The island was sold again, this time to Farquhar Campbell, in 1870, and at this point there were an estimated 600 Red deer on it.   The island was sold a third time, to John Bullough, in 1888 and remained in the Bullough family until it was bought by the Nature Conservancy Council in 1958, with the aim of using it as an outdoor laboratory.   In 1958 the first studies on the Red deer of Rum began, looking at grazing patterns, and since then the group (whom I have referred to as the ‘Red Deer Research Group’ throughout this article) has involved more than 30 scientists based at various institutions (Cambridge and Edinburgh Universities being the main two) and has done more to untangle the mysteries of Red deer ecology, behaviour and biology than any other group.   The RDRG’s work continues today, meaning that the Red deer on Rum have been under constant study for 52 years!   Anyone interested in reading more on the history and findings of the RDRG is directed to their website.

Deer parks provide an opportunity for many people to get a good view of animals that are otherwise generally fairly elusive and timid.   Every autumn photographers and naturalists flock to Britain’s deer parks and forests to try and catch a glimpse of the rut and this can lead to problems.   In parks, where deer are acclimated to human activity, they generally seem relatively at ease.   In a study published in the journal Animal Welfare during 1992, Jochen Langbein and Rory Putman report that although both Red and Fallow deer in Richmond and Bushy Parks (both in London) were disturbed by people nearby (i.e. they were more vigilant), this was transitory and there was no overall observable impact on the health of the deer.   However, this has not always been the case in deer parks and, as Norma Chapman points out in her book Deer, London’s Hyde Park used to have deer until they were moved to other parks in 1883 because there was a high incidence of dogs chasing deer into the path of oncoming vehicles; Richmond Park is now apparently experiencing similar problems today.   Similarly, human disturbance was tentatively implicated in the large die-off of Red and Fallow deer in Richmond Park during the mid-1980s.  

How significant human disturbance is on deer populations seems largely dependent upon how accustomed the deer are to humans.   Thus, although Richmond and Bushy Park deer (which are exposed to humans on a daily basis, often for long periods) may not be unduly affected, the situation can be very different in areas where the deer remain more secluded.   According to keepers in one area of the New Forest, for example, the Red deer rut is becoming an increasingly dangerous time as photographers place themselves too close to the action – in some cases, between two challenging stags!   In the case of the New Forest Red deer rut, the keepers have noticed a change in the deer’s behaviour and distribution patterns.   It seems that the increased disturbance is causing deer to move out of the region, increasing their susceptibility to traffic collisions and causing them to move into Sika (Cervus nippon) 'territory', where they are currently shot on site in a bid to prevent hybridization (see below).

Parks where deer are raised solely for the provision of meat, rather than to help maintain a landscape or for tourism purposes (as is the case with Richmond Park and the New Forest, even though culled deer are usually sold for venison) can be considered true deer farms.   John and Nickie Fletcher set-up the first commercial deer farm in Britain at Reediehill Farm, near Auchtermuchty in Scotland in 1974 and now, according to the British Deer Farmers Association, there are about 28,000 Red deer farmed commercially in the UK across some 300 farms – this represents almost 80% of the total number of deer farmed in the country.   Generally, stags are culled at between 15 and 17 months, whilst hinds are dispatched slightly later, at about 27 months old and the carcass is hung for at least a week before being processed by a butcher.   Venison prices in the UK are still fairly high and in early 2009 it was fetching about £1.50 (roughly US$ 2.35 or €1.73) per pound, which is about £3.30 per kilo – a topside or silverside steak of Scottish Red deer venison (from Dr Fletcher’s farm) will set you back about £27 per kilo (£12 per lb.).   In his book A Life for Deer Dr Fletcher unsurprisingly extols the virtues of venison as a healthier alternative to traditional livestock meat, pointing out that livestock are “rich in injurious saturates”, while most game species are rich in the fatty acids (e.g. omega-3 and -6 fatty acids) that are essential for body function and neural tissue (most notably brain) development.

Much has been made recently of the increase in deer poaching as a response to Britain’s entry into the global recession and, coupled with the bad weather of recent months, there has been an estimated 50% rise in deer poaching in the UK.   Invariably, some of this poached meat makes it into local butcher shops.   It should also be mentioned that not all venison available in the UK is from Britain and there is a considerable farming operation in New Zealand, the produce of which make it into some UK supermarkets.   Nonetheless, many local butchers obtain their venison, freshly shot, from licensed stalkers or deer parks.   If one considers that the deer may have lived all its life in an open park or forest before being dispatched by a trained and licensed stalker, it certainly seems to me to offer a potential source of meat to vegetarians who chose the diet solely on animal welfare (based around intensive farming and slaughterhouse conditions) grounds.

Death on the roads is a problem affecting both deer and motorists, although as some authors point out, it is often difficult to get a handle on how many collisions there are because many carcasses disappear in the boots of cars as venison – such carcasses are presumably either sold to local butchers or consumed by whoever found it.  (Back to Menu)

Road Traffic Collisions
When considering deer ‘in general’, it seems that road traffic accidents where motorists hit deer (also referred to as Deer-Vehicle Collisions, or abbreviated to DVCs) are a growing problem.   In 2007, the Deer Initiative published some preliminary results from their Deer On Our Roads survey, conducted in conjunction with the Highways Agency.   The results make rather depressing reading, showing that between January and December 2005, there were more than 30,500 reports of DVCs in Britain, of which nearly 25,000 (82%) occurred in England.   Worse still was that many -- perhaps, according to the Deer Initiative, as many as 80% -- DVCs go unreported and the total number per year could be 74,000 or higher!   The majority of DVCs involve Fallow, with Roe being the second most commonly struck – Red deer are rarely hit by vehicles and they, combined with Sika and Chinese Water deer make up only 3% of reported cases.   In Scotland, where Red deer numbers are higher, they accounted for 25% of DVCs.   According to the survey, DVCs involving Red deer were most likely to occur between October and January; the reasons are probably two-fold, with the nights drawing in (making driving conditions more dangerous) and the deer being more active (rutting) at this time of year.

In the 2009 Country File investigation on the subject of deer numbers in Britain it was estimated that there may be as many as 200 DVCs per day, with 20 people killed per year in such accidents – this leads to some £20 million (US$ 31m or €23m) worth of insurance claims per year.   The subject of DVCs, including methods being trialled to reduce their frequency, is covered in greater detail in the associated Q/A.

Genetic Diversity & Hybridization
The final aspect of human interaction I wish to cover is that of genetic diversity and hybridization.   It may seem peculiar to lump this topic in with human interaction, but it is human activity that has helped shape much of the history of Britain’s Red deer and it is the human taste for exotic animals that has caused hybridization problems.   The latter of these is covered in more depth in an associated Q/A and so will only be summarized here.

The British Isles is home to the largest population of wild Red deer to be found anywhere in Europe and the majority of these, some 300,000 to 400,000 animals, live on the Scottish mainland.   Red deer have been a constant feature of Scotland since the end of the last glaciation, 11,000 years ago, even though their numbers have subsequently waxed and waned.   As we have already seen, an increase in hunting has been largely responsible for increases in Red deer numbers during the 19^th Century.   Many of the deer used to increase numbers were from translocations (i.e. brought in from elsewhere).   Indeed, Britain has been subject to various introductions of Red deer from the continent in order to both bolster numbers and improve the quality of the animals already resident.   There don’t appear to be any reliable accounts of direct introductions of Red deer from Europe into the wild, but imports from Europe were made into deer parks.   Subsequently, where translocations occurred, deer were generally taken from parks, so it is not difficult to see how animals of European descent could be found in these populations.   Consequently, most British stocks are now expected to be allocthonous; in other words they’re not native to the area but reintroduced from elsewhere.   The Red deer on Rum are a case in point.   Genetic data presented in a 2006 paper to the journal Heredity by biologists at the University of Edinburgh indicate that the population on Rum is descended from at least two geographically separate ancestral stocks – one that’s closely related to Mediterranean and North African animals, and another from mainland European stocks.

The introductions and mixing of subspecies is, of course, not necessarily a problem because it can add much needed genetic diversity to a population and bolstering numbers can help bring populations back from the brink of extinction.   That said, it can also have some less desirable effects.   Recently concern was raised regarding the introduction of Fallow deer hybrids to Richmond Park.   These deer, which were apparently bred in Germany, have larger antler sets than the existing deer and this leads to fighting of mis-matched individuals, resulting in a higher injury rate among the deer.

Since the 1960s, evolutionary biologists have been investigating an idea that mutations (i.e. changes to genes) on strands of DNA can build up at a reliable rate; this is known as a molecular clock.   This means that by comparing the same DNA segments, or proteins, of two different species you can get an idea of how recently they diverged (split) from each other.   The idea is controversial, but has a large following.   Several studies published during the early-to-mid 2000s took fossil data and calibrated it using molecular clock estimates, concluding that Red and Sika (Cervus nippon) deer diverged between 5.2 and 7 million years ago.    Sika deer originate from Japan, but a small group were introduced to Powerscourt in County Wicklow, Southeast Ireland during 1860.   According to Derek Yalden in his The History of British Mammals, this introduction was so successful that Sika stags were transferred to many sites in Britain.   Dr Yalden lists several introductions of Sika in Britain, including 11 animals to the Carradale Estate on the Kintyre Peninsula on the west coast of Scotland during 1893, and several in Inverness (Scotland) during 1900.   There were also several cases where park Sika escaped into the wild (e.g. from Beaulieu in the New Forest during 1904), where populations were introduced to islands but swam to the mainland (e.g. from Brownsea Island in Poole Basin during 1896), and where the deer were deliberately released to provide hunts with quarry.   These releases (intentional or otherwise) were initially fairly contained, with populations remaining local until the early 1970s, when the maturing conifer forests and plantations allowed a dramatic range expansion.

Despite being separate species -- and this is one of the issues that muddies the waters when trying to define what a species actually is -- Red and Sika deer are sufficiently closely related to allow them to breed and produce fertile calves – in other words, they can hybridize to produce offspring that are genetically part Sika, part Red deer.   In his 2002 book, Dr Yalden notes that Red-Sika hybrids were reported as early as 1940, in the southern Lake District (Northwest England), and that it has been known for some time now that the deer living in the Wicklow Mountains of Ireland are neither entirely Red, nor entirely Sika, but a completely hybridized population.   Several fascinating studies have been conducted by Edinburgh University molecular biologist Josephine Pemberton and her colleagues and students looking at the phenomenon of Red-Sika hybridization.   In general the biologists have found that rates of hybridization are low -- a study of 735 deer, from 20 sites across Scotland, found that only about 7% were hybrids -- although in one particular population (at West Loch Awe in central Scotland) 43% of the deer were hybrids.   More interesting was that the majority of the hybrids couldn’t be identified as hybrids by the rangers employed to collect the tissue samples.   In many cases (including Red-Sika hybrids in captivity), hybrids display characters intermediate of the two parent species; that is, they look like a cross between a Red deer and a Sika.   In this case, however, it seems that there may be a domination of one particular phenotype (‘appearance’), which would make it very difficult -- if not impossible -- to selectively cull the hybrids out of the population.   Dr Pemberton and her colleagues suggest that hybridization is probably sporadic events, mostly between Red deer hinds and Sika stags.

Two questions often asked about the Red-Sika hybridization problem are something like: ‘Does it really matter if the two species mix?’ and ‘What can stop it happening?’   These are discussed at greater length in the Q/A, but I shall touch on them here.   There are biological, ecological and even psychological arguments (see Q/A) for preserving biodiversity (literally the ‘diversity of life’), but given that -- as the old adage goes -- ‘money makes the world go around’, there are also financial incentives for preserving the Red deer.    From a purely economic perspective, as we have seen there are many communities (especially in Scotland) that depend on Red deer as a source of tourism.   Indeed, on their website Scottish Natural Heritage point out that “Red deer are managed as a sporting resource on many Scottish estates”.   Will hunters pay £350 (plus travel, accommodation and meal costs) to shoot a smaller deer with a less impressive set of antlers?   Invariably some will, but I can’t help but think that demand will be lower, possibly much lower.

Generally-speaking, the best way to prevent the hybridization of two species is to keep them apart.   In the natural world, this separation can take many forms but can be roughly divided into physical barriers or biological barriers.   Physical barriers include a variety of features, including mountain ranges, roads, railway lines, lakes and rivers.   Biological barriers, by contrast, include obstructions such as different numbers of chromosomes (this usually leaves hybrids sterile, preventing them from reproducing), physiological adaptations that make mating difficult or impossible, differences in behaviour that mean the two avoid one another, and differences in habitat usage that prevents them from coming into contact.   Unfortunately, in the case of Red-Sika hybridization, introductions have placed Sika where they may not have been able to spread to on their own, thereby eliminating many of the physical barriers that they may have encountered.   Ultimately, without human intervention, Red-Sika hybridization would be impossible in the UK.   There are cases where barriers or intensive management (in the New Forest, for example) appear to be effective at keeping the species apart and there are also cases (e.g. in parts of Argyll, Scotland) where the two species use the same habitat in different ways and thus rarely encounter each other.   Nonetheless, many conservationists are concerned about the potential ‘merger’ and, in his 2002 book, Derek Yalden laments:

"The saddest change seems likely to be the total loss of the red deer through introgression [genetic mixing] with sika. … Conserving at least some native genotypes on the Scottish islands, safe from sika, seems essential.”

Dr Yalden is not alone in his concerns and, in a bid to protect the ‘Red deer genotype’ (i.e. to conserve pure-blood Red deer), Schedule 9 (Part 1) of the Wildlife and Countryside Act (1981) makes it illegal to release any Cervus species onto the Scottish islands of Rum, Islay, Jura, Arran and the Outer Hebrides.   Hopefully it is not too late to halt the loss of, to return to Archibald Thorburn’s quotation that began this article, “unquestionably the grandest wild animal we now possess in the British Islands”.  (Back to Menu)

Questions & Answers:

Why do deer roar?
What does testosterone do for stags?
Why are Sika deer problematic for Red deer?
What are antlers and what are they used for?
What are Chronic Wasting Disease and Tuberculosis?

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