Storm “Ashley” brought very strong winds to Ireland, Wales and most of northern England and Scotland last month, delivering torrential rain across much of the country through the weekend. Overall, however, last month was broadly a calm and mild month, with daytime highs in the mid-teens and nighttime temperatures frequently in double figures. This unseasonably mild weather continues as we move into November for all but Scotland.
Website news
Several updates have been made to the squirrel section, and a new article covering habitat preferences has been added to the European badger profile.
News and discoveries
Micro miracle. We're so used to hearing how species are in freefall in Britain, and it would be churlish to suggest this isn't the case, but there are some causes for positivity buried in the data here and there. You may have heard that in September Butterfly Conservation UK declared a “butterfly emergency” when the results of the Big Butterfly Count revealed the lowest returns in the survey's 14-year history. This is unquestionably cause for concern, but in brighter news, two gold-fringed dots (Bohemannia auriciliella), an extremely rare micro moth, were found during a nature walk at the Countryside Regeneration Trust's Bere Marsh Farm in Dorset last month. Fewer than a dozen of these tiny moths have been recorded in the UK to date.
Noisy neighbours. Washington and British Columbia's coastal waters are home to two populations of fish-eating killer whales (Orcinus orca), one in the north that has grown to an estimated 300 individuals, and a southern population of around 75. It's long been a mystery why the northern population has flourished while the southern has plateaued at such a low level. Now a paper published in Global Change Biology during September has provided an interesting insight, suggesting the waters are too noisy. Using mobile phone-sized Dtags to monitor the whales' movements and environmental conditions, including noise, the researchers found that as ambient noise increased the whales were less successful at hunting salmon. The biologists believe that vessel noise, particularly from boat propellers, interferes with the orcas' ability to echolocate.
Shake it off. Back in May 2020, I mentioned a new study showing how bees and some other insects had learned to bite plants to trigger them to flower as much as a month earlier than normal. Even when pollen is produced, though, it's sometimes secreted in anthers with small openings that make it tough for the bees to reach. In such cases, some bees have learned to flap their wings furiously when they land on the plant to shake the pollen out—a behaviour known as “buzz pollination”. Now, a new analysis of slow-motion videos of bumblebees visiting flowers has found that these insects take buzz pollination to another level, biting the anther and then vibrating their heads at high frequencies, allowing them to shake out much more pollen.
Seasonal highlight – Wild boar
Very few of us have seen a wild boar (Sus scrofa); fewer still have seen one outside of a zoo or farm. The ancestor of the domestic pigs we're familiar with today, this wild swine is an impressive beast. Females can weigh up to 95 kg (210 lbs. or 15 stone), while adult males may tip the scales at 150 kg (330 lbs. or 23 stone), standing up to 90 cm (3 ft.) at the shoulder. Measuring up to 150 cm (almost 5 ft.) in length, wild boar have a large muscular head and shoulders and a back that slopes down to a rump bearing a straight tail with long tassels of hair at the end. The powerful snout is long and narrow, ending in a flexible cartilage disc and, from the age of two years, male wild boar undergo extensive growth of their upper and lower canine teeth. These canines begin to protrude from under the lip and are referred to as tusks; continual growth throughout the animal's life means they may reach 6 cm (almost 2.5 in.) in length and give the animal a formidable appearance.
A dual-layered coat consisting of long dark brown guard hairs with pale tips, covering a thick woolly underfur pale brown in colour, gives boar an overall dark and brindled appearance. Coat colour ranges from white (leucistic), to fawn, to very dark brown (almost black). These imposing swine were once common in Britain's woodland and highly prized for their meat—their fearsome reputation made them a sought-after 'beast of chase'. Since the turn of the 14th century, the British public had some seven centuries to get used to the boars' absence from our woodlands. In recent years, however, wild boar have begun to re-establish themselves in our countryside, sparking debate about whether there is still a place for them in modern Britain.
A brief history of boar in Britain
In his 1999 opus on the history of mammals in Britain, the late Derek Yalden noted that the earliest fossil evidence of boar are remains found in Norfolk that date to the Cromerian interglacial in the Lower Pleistocene (600,000-45,000 BP). We don't know how important wild boar were to Palaeolithic hunters in Britain, but their bones and teeth turn up quite frequently in the remains of Mesolithic settlements and, along with red deer, they appear to have been a common game species. The introduction of the domestic pig to Britain during the Neolithic muddied the waters of the wild boar's archaeological record, because remains of the two are very difficult to separate. A very large ankle bone and canine discovered at Mount Pleasant in Dorset suggests boar were present in Neolithic Britain, but were either rare or rarely hunted. Archaeological accounts nevertheless suggest that, at the start of the Neolithic (some 6,000 years ago), there may have been in excess of a million boar roaming the vast tracks of oak, ash, lime, and hazel woodlands in the British Isles.
In his 2003 book on the wild boar in Britain, Martin Goulding described how, by about 1200 BC, large areas of woodland had been cleared to make way for agricultural land and livestock, including domestic pigs that needed to be herded into protective enclosures every night to prevent mating with wild boar and the boars attacking male pigs. This conflict, Goulding explains, in conjunction with the boars' habit of raiding crops and even their deep association with Celtic folklore (in which they were frequently presented as evil or malevolent) meant the writing was on the wall for Britain's boar, although the establishment of royal hunting preserves - such as the New Forest - by the Normans granted a stay of execution. Shortly after the signing of the Magna Carta at Runnymede in Surrey in 1215, however, historical texts suggest that boar numbers began running low and by the early 1300s a request for boar from the Forest of Dean by Edward II could not be filled, leading some historians to suggest that wild boar were extinct by this time. There are, nonetheless, stories up to the 1500s telling of brave battles between man and boar, and Oliver Rackham, in his 1997 book, argues that wild boar were rare during the Middle Ages and became extinct during the 13th century. Subsequent records of them being hunted pertain, Rackham believes, to reintroduction attempts; the dozen or so boar Henry III ordered killed for a friend in the Forest of Dean in 1260 were the last free-living wild swine in England.
In his chapter on the history of wild boar in Britain in Extinctions and Invasions, University of Sheffield archaeologist Umberto Albarella suggests:
“It is likely that the wild boar disappeared from Britain as a consequence of a combination of habitat depletion (mainly woodland), over-hunting and eventually inter-breeding of the final relict populations with free ranging domestic pigs.”
Albarella notes that precisely how long Britain remained boar-free remains contentious owing to various reintroduction attempts. He also illustrates that there was some confusion among people even at the time, recounting an interesting discussion between a French and English herald that took place during the late 1600s. The French herald teases the English for not having any fierce animals in their countryside—such as the wolf, lynx, or wild boar—that require bravery to hunt. The English herald replies that, although lacking wolf and lynx, they do indeed have wild boar. So, perhaps wild boar were at large in the British countryside during 17th century. By the 18th century, however, boar could no longer be found in the country, and Albarella comments that the meat had disappeared from British tables by this time. It was in the late 20th century that efforts to farm boar resumed in earnest and Martin Goulding provides a comprehensive summary of this in his book, Wild Boar in Britain, from which much of the following is summarised.
Wild boar have been farmed in Britain for several decades. Early attempts were on a comparatively small scale, although there were sporadic reports of animals escaping during the 1970s. Goulding explains that the first major boar farm began in Cambridgeshire in 1981 using surplus animals from London Zoo that were descendants of French stock. Throughout the 1980s farmers sought to increase the carcass weight of their herd and imported stock from Germany and Sweden. Unfortunately, the British government doesn't differentiate between wild boar and domestic pig stock, so there is no official register of breeders or stock origin/mixing. Nonetheless, Goulding suggests that the popularity of boar farming grew from about three licensed breeders with a total of 38 animals between them in 1988, to some 40 breeders with 400 sows that produced about 1,500 animals per year for slaughter in 1994. In a report published in 2000, the Department for the Environment, Farming and Rural Affairs (DEFRA) stated that there were 4,554 wild boar farmed in Britain. Goulding colourfully describes boar as “the Houdinis of captive livestock”, pointing out that their strong narrow snout and large head supported by powerful shoulders are ideal tools for undermining and levering up stock fencing. Long legs make them speedy, and they jump more akin to deer than swine. As such, at least 60 animals escaped from six different farms in six different counties between 1983 and 1994. The great storm of 1987 blew down a section of perimeter fencing at a boar farm in Tenterden, Kent, and several boar were rumoured to have immediately upped sticks and left.
Various sightings of wild boar and complaints of damage caused by their foraging (rooting) were reported to authorities in Kent during the late 80s and early 90s; these were often, rather curiously, put down to badgers. In 1994, however, a hunter in Beckley, East Sussex (just across the Kent border) shot two boar on his land, and damage to a maize crop in Aldington (southwest Kent) two years later was attributed to boar and led to several being shot in adjacent woodland. Goulding found evidence of wild boar in much of the wooded areas on the Kent/East Sussex border in 1996, and further signs of boar in Dorset, a population believed to have been founded by animals escaped from a farm near Bridport. In October 1998, Goulding and Graham Smith confirmed the presence of two free-living populations of wild boar in Britain: one on the Kent/East Sussex border and another in Dorset. Six years later, in 2004, the Kent/East Sussex population was estimated to be about 200 animals, with 30 or so in Dorset, and there was confirmation of a third population, containing “a significant number” of boar, in Hertfordshire. Since then, numbers appear to have fluctuated significantly. In the Forest of Dean, for example, the Forestry Commission operate an annual cull in a bid to maintain a stable boar population of about 400 individuals. In 2012 the cull was suspended because numbers dropped and there were concerns the species may become extinct in the forest, but the following spring 535 animals were counted, and this had increased to 819 the following spring in spite of a resumption of culling. There currently no recent official estimates for the number of boar in Britain, but some sources suggest there may be as many as 4,000 animals.
In terms of distribution, to date, populations have been identified in just over 40 locations across England, Wales and Scotland, including Hampshire, Gwent, Cheshire, Yorkshire, Tayside, south Devon and the Brecon Beacons. In a paper to the journal Wildlife Biology in Practice in 2014, however, Charles Wilson argued that there are only four sustainable populations: the oldest one in the Weald area of Kent/East Sussex, the largest in the Forest of Dean, and two with an unknown number of animals in south Devon and the Brecon Beacons.
Being boar-ing
Wild boar are primarily nocturnal, commencing activity about an hour before sunset and returning to rest sites before sunrise, and there is an increasing tendency for night-time activity in areas where they are hunted. In the UK, Goulding found they spend most of their time resting in dense cover and—following a short period of grooming and/or wallowing upon waking—feed actively for between four and eight hours per night, often interspersed with short bouts of rest. Tracking studies in Europe have found boar to be active 40-65% of the time, during which they walk at an average speed of about half a mile per hour (one kmph), increasing to almost four mph (six kmph) at a trot; boar in full flight have been clocked at 25 mph (40 kmph). They can swim well (reports of them crossing rivers and swimming off coastlines are relatively common) and jump obstacles up to 120 cm (4 ft.) high from a standing start. Their vision is generally considered to be poor, although it is shifted to the blue end of the spectrum which makes them fairly good at spotting movement in poor light, while their sense of smell and hearing is acute, with a much higher frequency range than ours (i.e., 42-40,500 Hz).
Males move more during the rut when searching for receptive females, while females cover the smaller areas during the fortnight or so after their piglets are born in the spring. In general terms, females tend to have smaller ranges than males, up to about three and seven square miles (8 and 18 sq km), respectively. While feeding, the animals leave some distinctive field signs that allow damage to be separated from that of other 'rooting' species, such as badgers. In his book, Wild Boar in Britain, Goulding described how rooting is generally characterised by a few small patches of highly disturbed (rooted) soil and small mats of overturned turf at the edge of the rooted area. The absence of scratch marks that would be left by badger claws and the presence of hoof prints should also confirm boar or pigs as the culprits. (It should be mentioned that it is impossible to separate the rooting damage made by domestic pigs from that of wild boar.)
Rooted patches may overlap such that, over a couple of nights, an entire lawn may be dug up. Boar will also wallow in mud, particularly during hot weather, as their lack of sweat glands makes cooling off difficult, and this behaviour is often followed by rubbing on nearby trees to remove parasites and moulting hair—favoured trees can have sections of their bark rubbed off. Smaller trees may have notches taken out of their bark by the tusks of sexually active boars—pheromones in the boar's saliva leave a scent to act as a territorial marker during the rut.
Wild boar have an interesting social structure, being neither particularly gregarious nor entirely solitary; they lie somewhere in between. Goulding divided individuals into one of three social group types. The first is adult females, which tend to live in small social groups, consisting of a dominant sow and a handful of other mature females along with their most recent piglets and some survivors from previous litters—called sounders—that vary from about six to thirty individuals. The second is the lone adult males; ordinarily solitary, and particularly so during the breeding season, they will only tolerate the presence of other males at good feeding sites outside the rut. The final group type is the young adults of mixed sex. Young males are often driven from a sounder by mature boars during the rut and these displaced animals form loose-knit bachelor groups that move around and feed together, sometimes incorporating young females. The composition of groups changes as females leave to give birth, new females arrive from elsewhere, and existing females depart, sometimes returning later. Different groups of boar may share the same resting and wallowing sites, but Goulding noted that they retain their social identity (i.e., individuals don't intermix).
Pigging out
Wild boar are omnivores. Invariably the bulk of the diet—90% according to some analyses—is made up of plant material and small invertebrates. Boar root for bulbs, tubers, shoots, young roots, broad-leaved grasses and a variety of fruits, including acorns, chestnuts and beech mast. The bulbs of bluebells are also rooted for, particularly during the spring and summer. Rooting involves turning over typically small patches of leaf litter, vegetation and topsoil; patches may overlap to form a mosaic and each patch is 5-15 cm (2-6 in.) deep. In agricultural landscapes, potatoes, grain, sugar beet and other crops may be taken. In Italy's Maremma Natural Park, Giovanna Massei and her colleagues found that energy-rich foods such as acorns and olives were actively sought, while pine seeds were also readily eaten even when quantities were low. Acorns and olives accounted for most of the diet when they were abundant, but graminoids (grasses and sedges) and juniper berries supplemented the diet when the former were scarce, particularly during summer. In fact, graminoids were staple throughout the year and at times accounted for up to 98% of the diet. Other fruit was also taken, including blackberries, wild apples, and figs.
Goulding, in his 2003 book, noted that small mammals (e.g., mice and voles), nestlings, small birds, eggs and carrion are taken as the opportunity arises. Massi and her colleagues found the remains of birds, small rodents, porcupines and lizards in wild boar scat, as well as a variety of invertebrates (mainly beetle larvae, caterpillars, molluscs and worms) the latter featuring most frequently between May and July. How important carrion is in the diet of wild boar isn't known, but it has been suggested that they may scavenge the kills made by predators and thus benefit from the presence of wolves and lynx. This may be of particular importance in northern parts of their range as snow depths more than 20 cm (8 in.) can prevent rooting, and bad winters in Poland can decimate local populations. There is also an interesting account of a group of boar driving a lynx away from its kill.
Lean, mean, piglet-producing machines
Female boar become sexually mature at around 18 months old, and many will conceive during their second year. Male boar, by contrast, don't reach sexual maturity until about two years old and many won't mate until the age of five. Wild boar have a well-defined rutting period that runs during late autumn and early winter, peaking in November. The shortening of the days triggers a surge in testosterone that prompts males to become entirely intolerant of one another, while nutritional status is an important determinant of whether a female comes into oestrus. The males will chase females, champing their mouths as they do so to generate a pheromone-laden saliva that appears to encourage the sow into oestrus. As with deer, the rut is the sole focus of the males and they may not eat for the duration, resulting in a loss in body weight of some 25%. A sexually mature male will join the sounder and try to drive off any males loitering in the group. Fights between evenly matched animals can be intense, but males lay down additional fat under the skin of their neck and shoulders (reabsorbed after the rut) to help reduce injury. Once all the receptive females in the sounder have been mated, the male will leave in search of other females.
Females give birth (a process called farrowing) during the spring after a roughly four-month gestation. In his Wild Boar in Britain, Martin Goulding describes how a sow builds her specially constructed nest: she'll leave the main social group and dig a shallow scrape in the ground which she lines with twigs and grass. A mound of vegetation from the surrounding area (e.g., bracken, reeds, and twigs) is piled on top of the nest to a height of about a metre before the sow pushes her way inside to give birth to 4-6 piglets under the shelter. The nests are exceptionally well camouflaged, and females are very protective mothers, so Goulding advises against searching for farrowing nests. Generally, a sow will produce a single litter in any given year, but in exceptional mast years the young can be weaned by April, allowing the female to come back into season to be mated again.
Piglets are born with a light brown coat and yellow longitudinal stripes (some authors refer to newborn piglets as 'humbugs' because of this coat pattern) that is replaced by a uniform reddish-brown coat by the time the piglets are weaned at around 12-16 weeks. This 'red phase' coat (like that of a red squirrel) is replaced in the second year. The piglets will leave the nest with the sow after about two weeks, but Goulding noted that they don't join the social group until they're 4-5 weeks old, at which point the mother associates closely with other sows who have given birth at the same time, allowing cross-suckling. Indeed, females in the sounder synchronise farrowing such that all litters are born at the same time. The result is that the piglets of several sows may form crèches in which they play fight, with the sows taking turns keeping an eye on them. In captivity boar can produce upwards of ten piglets in a single litter, but groups of ten or more piglets in wild animals appear more likely to be mixed litters.
The sex ratio is broadly 1:1, although a fascinating study led by Sabrina Servanty at the Universite´ Lyon in France found marked changes in the sex ratio of wild boar associated with litter size. Servanty and her team studied 254 litters from wild boar harvested in Chateauvillain-Arc-en-Barrois forest in eastern France and found a greater proportion of males in litters of six piglets or fewer, while females predominated in larger litters. This makes sense when considered in the context of the results from Maremma National Park. When times are tough, litter sizes are small and there's a tendency to produce males, which are more likely to disperse and not hang around using up already scarce resources. When times are good, more females are produced; females are more likely to remain and increase the group size.
Changing the landscape in a changing landscape
The reappearance of wild boar in the British countryside after an absence of some 700 years has prompted concerns about whether they are in fact a welcome addition to our fauna. Many conservationists point out that boar were once native to Britain and played an important role in the ecology of our woodlands. Opponents of the boar note, however, that our countryside has changed a lot in the last seven centuries, stabilising in the absence of these animals and, as such, wild boar no longer have a place in it. Indeed, in a 1986 review of species introductions published in the journal Mammal Review, Derek Yalden wrote:
“British habitats have developed and stabilized in its absence for over 300 years. Its reappearance could be highly disruptive. Unlike the time when the Boar was a widespread and common species here, many forests are now subject to intense management or recreational pressures; many have additional deer or feral mammals present. Few are large enough to withstand the impact on tree regeneration of Boar populations as well as these other animals. There is also the problem, as with some other potential reintroductions, that if the project is successful, as intended, the population might expand and trespass on neighbouring habitats where it will be unwelcome.”
The cost of rooting to agriculture has yet to be formally assessed, but the highly seasonal nature has led some to suggest that targeted supplemental feeding of the boars could help reduce the impact. Looking at 58 reports of grassland rooting damage by wild boar in Dorset between spring 1997 and autumn 2002, DEFRA wildlife biologist Charles Wilson found that three-quarters occurred between January and March and, overall, most damage happened in fields adjacent to woodland. Feeding and targeted culling during these key times are considered beneficial in reducing the impact. Concerns have also been raised about their habit of eating carrion and ingesting soil while rooting can leave them with heavy parasite burdens that could be transmitted to people or livestock.
Data from Sweden, where boar have been accidentally reintroduced, suggest that their rooting activity has increased species diversity in some habitats, but the picture is far from clear. Certainly, the disturbance caused by rooting boar favours some species over others, and their active rooting for the rhizomes of bracken during the winter might be beneficial in controlling this and other forest weeds. Conversely, a study on the impact of wild boar rooting on the soil chemistry and sapling growth in an area of heathland and forest in Veluwe in the Netherlands between January 1991 and May 1995 concluded that “... regular rooting negatively affects the deciduous regeneration potential...”. It seems the boars' activities had no effect on soil chemistry (i.e., pH, organic matter content, nitrogen content) and did nothing to mix the soil horizons or promote germination of any of the tree species in the forest—indeed, it had a negative impact on the germination of oak and beech.
Concern has also been raised recently about the decline of bluebells in British woodlands and whether boar might expedite this; some areas have lost half their blooms in the past 25 years. A team of biologists at the University of Sussex, led by Natasha Sims, investigated the impact of wild boar rooting on the ecology of bluebells in Bixley and Beckley Woods in England. They found that immediate effects were that rooting significantly reduced the percentage cover (90% down) and density (60% down) of plants, and adversely affected the number of flowering stems. Cessation of rooting brought about by excluding the boar enabled substantial recovery within two years assisted, they conjecture, by a positive effect of rooting on germination. The biologists explain:
“Recovery may have been assisted by the positive effect that rooting had on germination. The greater germination success in seeds from rooted open plots compared to un-rooted protected ones strongly suggests a positive influence of disturbance, perhaps through exposure of dormant seeds in the soil or suppressive effects on competing species. Indeed, this result may indicate that bluebells are adapted to rooting as a consequence of a long prior history of co-occurrence with boar.”
So, the boar appear to have a significant impact on bluebell cover, but the plants are able to recover rapidly if the rooting pressure is managed. The impact of long-term and persistent rooting on bluebells has yet to be investigated.
Finally, concerns have been raised over the potential for boar to attack people and pets, as well as be involved in road traffic collisions. Generally, most observers are quick to note that wild boar are secretive and seldom seen. Goulding, in his 2003 book, wrote that “Contrary to their fierce reputation, wild boar will avoid human contact whenever possible” but reports of people being charged by the animals have made the headlines. Similarly, road collisions are invariably a potential problem, particularly during the autumn when the nights draw in and the males are rutting and thus moving more. The greatest risk exists where roads transect woodland. To the best of my knowledge, no formal stats exist for how many wild boar are killed on the roads in Britain. Interestingly, however, Henrik Thurfjell, at the Swedish University of Agricultural Sciences, and colleagues studied the behaviour of wild boar around roads in southern Sweden between 2004 and 2007, and their results suggest that wild boar appear to make behavioural adjustments that reduce the risk of close vehicle encounters—the females they tracked were significantly less likely to cross roads when traffic volumes were high.
Given the changing nature of our landscape, it is valid to ask whether boar have a place in it any longer. At the same time, are these fears legitimate or do they represent British people having become more 'zoophobic' after centuries of living without species that many see as large and dangerous in our landscape? There is little doubt that boar have established themselves in parts of Britain now and some form of management is going to be required if we are to coexist with these animals.
For a round-up of Britain's seasonal wildlife highlights for late autumn, check out my Wildlife Watching - November blog. To learn more about the pannage season, which draws to a close this month, check out Pigging Out on the Forest.