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BATS

Content Updated: 14th June 2006

Bats are an amazingly diverse group of mammals, found throughout the world (with the exception of the extreme Polar regions). This summary, however, will deal primarily with those species resident to the UK.

Parti-coloured BatTaxonomy: Contrary to popular misconception, bats are not flying rats – indeed bats are not even of the rodent Order. Scientists often refer to bats as Chiropterans. Globally, the Order Chiroptera (from the Latin “hand wing”) is currently composed of 18 families, about 174 genera and more than 900 species. Chiropterans are subdivided into two main groups (suborders): Megachiroptera (the Old World Fruit Bats or Flying Foxes) and Microchiroptera (any bat that isn’t a Fruit bat!). There are some 164 species of Fruit bat, grouped into 41 genera in a single family, the Pteropodidae. The Microchiroptera is the larger of the suborders, consisting of the remaining 17 families, 133 genera and somewhere in the region of 743 species. Of the Microchiropterans, the most diverse family is probably the Phyllostomidae (the New World Leaf-nosed Bats), with 49 genera, and the largest family the Vespertilionidae (Vesper or “Evening” Bats), with an impressive 308 species divided into 34 genera. (Photo: Parti-Colored Bat, Vespertilio murinus.)

As with anything taxonomic, there are -- metaphorically speaking -- hundreds of different classifications for bats. The one I choose to follow is the one presented by David MacDonald in his 2001 revision of The New Encyclopedia of Mammals. Each classification arranges the bats slightly differently and there are many aspects of chiropteran classification that remain highly debatable. For example, up until the late 1960s and early 1970s the majority of bat cladists considered that these winged mammals form a monophyletic group (in other words, they are each other’s closest relatives); this idea basically means that powered flight only evolved once in mammals. However, studies on the brains of Fruit bats in the mid-1980s led by Prof. John Pettigrew at the University of Queensland’s Neuroscience Lab to suggest that the mega- and microchiroptera evolved independently from two separate groups of non-flying mammals – this idea is often referred to as the diphyly hypothesis. Indeed, Pettigrew found that megabats had very advanced neural pathways between the eyes and brain, more akin to that seen in primates (monkeys, apes and humans). Ergo, if bats are truly diphyletic (i.e. they don’t form a single group that evolved from a common ancestor) then flight must have evolved twice: once in the megachrioptera (megabats) and then again in the microchiroptera (microbats).  So, which of these hypotheses seems to be the most likely? However appealing Pettigrew’s evidence may be, based purely on the available evidence it seems at this point that bats are a monophyletic group.  Diphyly has only been supported by a couple of studies: one looking at bat nervous systems and another at bat penis morphology. Conversely, there are upwards of 30 studies supporting the notion of chiropteran monophyly. Ergo, although the jury is – to some extent – still out on the monophyly/diphyly debate, the general consensus is that bats form a single group that evolved from a single, non-flying, common ancestor.

The UK is home to 16 species of bat and, in their book A Field Guide to British Bats, Frank Greenaway and Adam Hutson list seven species that are vagrants. Only 12 years ago, there was a seventeenth species on the British bat fauna list: the Mouse-eared Bat (Myotis myotis). In January of 1990, this charismatic little bat was declared extinct in the UK -- the first mammal to become extinct in this country since the extirpation of the wolf back in 1745 -- after two year’s worth of bat censuses failed to find a single individual. However, there was a glimmer of hope recently, when a young Mouse-eared bat was found hibernating near Chichester in West Sussex during the winter of 2002. Although this finding alone is insufficient to reinstate this Myotis bat to our list of extant fauna -- numerous efforts to find an individual during the following summer resulted in failure -- it does represent a slightly brighter future for those bat conservation workers in Britain.

The following example traces the basic taxonomic hierarchy of the Lesser Horseshoe Bat (Rhinolophus hipposideros). For more information and a description of how we classify living organisms, see my Taxonomy page.

Kingdom: Animalia (Animals)
Phylum: Chordata (Possess a basic 'backbone')
Class: Mammalia* (Mammals)
Order: Chiroptera (Bats)
Sub-Order: Microchiroptera (Micro-bats)
Family: Rhinolophidae (Horseshoe and Old World Leaf-nosed Bats)
Genus: Rhinolophus
Species: hipposideros

* For those more taxonomically-minded of you, some authorities further divide the Mammalia, placing bats into the Infra-class Eutheria and the Cohort Unguiculata. The precise meaning of these extra groupings is beyond the scope of this website, but suffice to say it is a more comprehensive way of grouping certain mammals. (Back to Menu)

Size and Weight: Quite intriguingly, there seem to be no accurate accounts of the largest bat ever found. Most texts go so far as to say that the Flying Foxes (megabats) are ‘amongst the largest of bat species’ with some individuals reaching wingspans in excess of 1.7m (about 5.5 ft) and exceeding a kilogram (just over 2lbs) in weight.  Conversely, the record of smallest bat species is held by the Kitti’s Hog-nosed Bat (Craseonycteris thonglongya) with a wingspan of only 16cm (just over 6 inches) and, according to David MacDonald’s New Encyclopaedia of Mammals, a weight of 1.9g (about 0.07 oz) – indeed this is the smallest mammal known to science. Among the British bat species, the largest are the Horseshoe bats (Rhinolophidae), Noctule (Nyctalus noctula) and Serotine (Eptesicus serotinus), which are all of roughly equal size – of these, the Noctule is arguably the largest. Were the Mouse-eared Bat still a listed UK species, this would -- just about -- be our largest chiropteran.

Common pipistrelleThe smallest British bat species is the Pipistrelle (Pipistrellus pipistrellus - 2 week old pup, right, the largest of which reach about 8cm (about 3 in.) long and weigh 8.5 grams (up to 0.3 oz.); ordinarily, pipistrelles reach about 4cm (1.5 in.) and weigh only 5 grams (0.176 oz.). Incidentally, recent DNA studies have revealed that, what was originally thought to be a single species (P. pipistrellus) is actually two species that look very similar (P. pipistrellus and P. pygmaeus).  This, so-called pipistrelle split, is covered in more detail on the Questions and Answers page. (Back to Menu)

Colour: Generally speaking, most people tend to think of bats as being either brown or black in colour – interestingly, some people I spoke to were even unaware that bats are covered in fur. The colour of this fur varies between species, from the more typical brown or black -- usually paler underneath -- to a pale orange in the Schneider’s Leaf-nosed Bat (Hipposideros speoris). Certain bats fall in between this, displaying coloured patches, stripes or frosted tips to their fur.  (Back to Menu)

Distribution: Bats are found throughout the tropical, sub-tropical and temperate latitudes. Indeed, with the notable exceptions of very high mountains, isolated oceanic islands and extreme polar latitudes, bats are found worldwide. Chiropterans seem especially diverse in South-east Asia, New Guinea, Australia and certain Pacific Islands (e.g.  Guam). The most widespread of the British bat species is the Pipistrelle, a common bat throughout the UK. The Daubenton’s bat (Myotis daubentoni) is also widely distributed in the UK, as is the Brown Long-eared bat (Plecotus auritus). The same, however, cannot be said of the Grey Long-eared bat (Plecotus austriacus), which is restricted to southwest England, especially along the south coast and the Channel Islands. Most of our chiropteran fauna are found throughout England and Wales, but are rather more sparsely distributed in Scotland. Indeed, in his 1985 book, Phil Richardson notes that Britain has 15 resident species, while Ireland has seven and Scotland only two. Judging by the last reliable bat census (published in the Atlas of Mammals in Britain, 1993) there are now four species found in Scotland (with a couple of vagrants surfacing in the South-west regions). The two most widely distributed Scottish species are the Greater Horseshoe (Rhinolophus ferrumequinum) and Pipistrelle bats. (Back to Menu)

Longevity: As with any animal, once over a year old, survival chances improve dramatically. It is obviously difficult to obtain lifespan data for wild animals, particularly elusive, nocturnal ones. However, tagging studies and the rearing of bats in captivity have provided some elucidation as to how long these mammals live. Marked bats have been known to live in excess of 20 years, and a Little Brown bat (Myotis lucifungus) in Canada was documented to live for 30 years. In his fascinating 1985 book, Bats, science teacher and Bat Conservation Trust chairman Phil Richardson gives maximum ages for the Greater Horseshoe, Lesser Horseshoe, Mouse-eared, Daubenton’s and Pipistrelle bats as 31, 18, 28, 32 and 11 years, respectively. Richardson also gives a longevity of 20 to 30 years for Fruit bats. MacDonald in his New Encyclopaedia of Mammals gives the maximum age for chiropterans as 33 years, although longevity “probably averages 4-5 years in many species”. (Back to Menu)

Sexing: Without actually getting hold of the bat, sexing can be a remarkably difficult task. If you can nab the little blighter for long enough to scrutinize it, sexing is reasonably simple; if it has a penis it’s a male. However, as it is illegal to ‘nab’ bats without a bat handler’s license in this country, most people will not get close enough. Unfortunately, it is not always true to say that males are larger than females (or vice versa). The variation between different bat species means that in some species females are larger than males, while in others the reverse is true and in many species the difference in size between sexes is negligible. During, and directly prior to, the mating season the testicles of males may descend from the scrotum making sexing a little easier. (Back to Menu)

Basic bat anatomyActivity: Most people would consider bats to be ‘creatures of the night’ and this is, for the most part, an accurate surmise. There are some species -- such as the Old World Fruit Bats -- that venture out to feed during daylight, but most (if not all) microbats are nocturnal.  Although Fruit bats may be active during the daylight hours, there is a noticeable crepuscular peak in activity (in other words, Fruit bats are most active during the dawn and dusk hours). Some microbats, such as the Whiskered Bat (Myotis mystacinus), may also be seen during the day, but such observations are rare.

Pipistrelles are probably active for the longest period of any British bat: from March through to the end of October or November. Most British bats have a somewhat narrower activity span, generally emerging from hibernation at the end of April or beginning of May. Time spent foraging for insects and other prey varies from species to species and according to season. For example, Greater Horseshoe bats (Rhinolophus ferrumequinum) feed intermittently throughout the night from May to August, staying away from their roosts all night from late August.  Conversely, Common Pipistrelles (P. pipistrellus) spend much of the night foraging for insects during May and June, returning to their roosts between midnight and daybreak. Pipistrelles then appear to adopt a bifurcated feeding activity pattern from June to August whereby they have a peak just after sunset and another before dawn; intermittent feeding may pervade such peaks. Frequently, feeding duration is affected by weather conditions and there will usually be a premature truncation of feeding on colder nights, with bats returning to their roosts earlier. The time taken to emerge from a roost also varies according to species. In their Field Guide to Mammals of Britain and Europe, David MacDonald and Priscilla Barrett give summer emergence times for the Common Pipistrelle, Daubenton’s bat (Myotis daubentonii), Greater Horseshoe bat and Natterer’s bat (M. nattereri) as 20, 30, 50 and 60 minutes after sunset, respectively. Nocturnal activity in Fruit bats tends to begin about 30 minutes after sundown. Many bat species will also occupy ‘night roosts’ to provide some shelter and security between nocturnal feeding bouts. In certain species, these night roosts may also be used as a sort of banquet hall with the bats bringing their quarry back to the temporary roost in order to consume it; this seems to be especially true of Fruit bats. (Image: Basic bat anatomy - click to enlarge.)

Bat activity is often also related to various topographic and barometric influences. In his 1995 paper in the journal Functional Ecology, Ken Paige at the Institute for Environmental Studies at the University of Illinois reported that some bats were able to detect changes in barometric pressure -- in other words, they are able to sense the changes in atmospheric pressure usually associated with changes in weather conditions -- and use this information to decide whether or not it is worth the time and effort to go out looking for food. Paige found that more bats emerged from their roost during nights when barometric pressures decreased (a meteorological sign of impending rain). Indeed, barometric pressure accounted for some 87% of changes in bat activity. It seems that bats can detect variations in atmospheric pressure using their Vitali organ, which is a receptor in their middle ear. The Vitali (or Paratympanic) organ is normally encountered in the ears of birds, which are also believed to use it to detect changes in atmospheric pressure. This organ has recently been demonstrated in alligators by Chris von Bartheld and a colleague at the University of Nevada, Reno, although it appears that bats are the only mammals known to possess a true paratympanic organ (some mammals possess a very primitive organ which may contribute the same function). The advantage of such a sense is that the bats can determine the likelihood of insects being abundant and thus whether it is worth expending the energy to leave the roost and hunt for them. Up to a point, insects tend to be more numerous during low-pressure weather systems; pressures of around 960 mm Hg, however, signify heavy rain and this will suppress insect activity. Ergo, if barometric pressure is too low, the bats can decide to stay in the roost and not expend precious energy looking for prey that is likely to be scarce.

MoonBat activity can also be related to celestial factors, specifically moonlight. In a fascinating paper in the journal Current Science back in 2002, Dr. Ganapathy Marimuthu and a colleague at the Madurai Kamaraj University in India, report on the effect of the lunar eclipse of 9th January 2001 on the foraging activity of Short-nosed Fruit bats (Cynopterus sphinx) in a Black Grape (Vitis vinifera) orchard in the Cumbum Valley, South India. Marimuthu and Singaravelan observed a three-fold increase in bat visits to the orchard during the eclipse (which lasted from 12.30 until about 03.15) compared to the days before and after the eclipse. The researchers suggest that this suppression of foraging activity by bats on brightly moonlit nights is an adaptation to avoid nocturnal predators. During their study, Marimuthu and Singaravelan observed a Barn owl (Tyto alba) and a Great Horned owl (Bubo bubo) perching in trees in the vicinity of the orchard, although no interaction between the birds and bats was witnessed.

In their 1999 paper, Scott Grindal, Joe Morisette and R. Mark Bringham at the University of Regina in Canada, found that the activity of bats in British Columbia tended to be higher at lower elevations.  Indeed, bat activity was as much as 40 times higher in river habitat than in upland (higher altitude) areas of the same forest. Grindal and his colleagues looked at bat activity at three different elevations in a forested area of British Columbia during the summers of 1993, 1994 and 1995. Not only did they encounter more bats in the lowland riparian (river) habitats, they also observed a sex bias in the captured bats: more female bats were caught in lowland regions, whilst males were more frequently encountered at higher elevations. The scientists put this increased activity at lower altitudes down to river habitats supporting a more prolific source of food; it was also suggested that bats may use such rivers as a source of drinking water. Although there are several reasons for the sex bias observed, it was deemed possible that females may preferentially seek-out river habitats because of the abundance of insect prey they support. Males, on the other hand, may opt for higher altitudes (and colder temperatures) to conserve energy. A similar study published in 2003, by Janet Erickson and Michael Adams at the University of Washington, found a four-fold increase in bat activity at low elevation sites compared to high elevation sites in the Capitol State Forest of western Washington. Moreover, the biologists found that feeding activity was 20-times greater at lower than at higher elevations. Intriguingly, this scenario doesn’t seem to hold true for all bat species. Erickson and Adams found that the non-Myotis group of bats (i.e. the chiropterans they encountered that weren’t Mouse-eared bats) showed no significant variation in activity at the different altitudes. The authors suggest that such differences may be a result of differences in insect availability, climatic conditions and morphology (bat “design”) of the bat species.

Cornish mixed farmlandFinally, a fascinating paper by Bristol University PhD student Lait Wickramasinghe in the Journal of Applied Ecology during 2003 found that bats seemed to ‘prefer’ organic farms over conventional ones.  Organic farms are those that largely exclude the use of man-made fertilizers, pesticides, growth regulators and animal feed additives.  Wickramasinghe and his supervisors compared the activity and species richness (i.e. the number of different bat species) on 24 matched pairs of organic and conventional farms during 2000 and 2002, reporting that bat activity was 61% higher on the organic farms, especially over areas of water. The biologists also found that 14 of our 16 native bat species were found on the organic farm while only 11 were encountered on the conventional farms. I should point out that a difference of only three is not, statistically speaking, a reason to conclude that organic farms have more species that conventional ones. Populations have declined for many species of British bat, and studies such as this provide an interesting insight into how we might stop -- and possibly even reverse -- this decline. One of the main reasons for the observed preference of organic farms may lie in the hedgerows. Bats use walls, hedgerows and woodland edges as flight paths, because such areas often provide shelter for aggregations of insects. Indeed, the Bristol researchers found that hedgerow height affected the number of feeding “buzzes”, with more buzzes along higher hedges. (Back to Menu)

Hibernation and Torpor: Bats are among only three British mammals that truly hibernate (the others being hedgehogs and dormice). During the colder winter months in temperate regions there are too few insects to make hunting an energetically worthwhile activity. Thus, in order to circumnavigate this veritable famine, microbats hibernate to conserve energy. As I cover in more detail in the Questions and Answers section, hibernation is more than merely sleeping. In his book Bats, Phil Richardson notes that, during hibernation, a bat’s heartbeat can drop to about 20 beats per minute (bmp), taking about five breaths per minute.  This is a significant decrease for a microbat, which may have heart rates as high as 900 to 1000 bpm during feeding. Such heartbeat rates are high for mammals; while typing this, my heart is beating about 70 times per minute and I’m taking some 20 breaths; my heart would give out long before it reached the beat frequency of a feeding microbat. The idea of all this is that by lowering their heart rate and metabolism (oxygen consumption can drop to one hundredth of waking rates) the bats burn fewer calories per unit time and can make any energy source -- be it a meal of insects or fat reserves -- last longer. In a 2003 paper for the journal Doklady Biological Sciences, a group of Russian scientists report on the hibernation of two species of Vesper (so-called ‘evening’) bats in central and southern Yakutia (a territory in the extreme North of Asia). The biologists found that the body temperature of hibernating Northern (Eptesicus nilssoni) and Brown bats (Plecotus auritus) only slightly differed from the ambient; both the bat’s body temperature and the environmental temperature trailed each other precisely between two and zero degrees Celsius (35.6 and 32 deg-F). The team also report that the periods of hypothermia in bats lasted for 2 ½ weeks and that -- in principle at least -- bat hibernation resembles that seen in rodents.  Intriguingly, the paper also notes that, despite the common sight of hundreds of bats grouped close together in a roost during periods of rest, the hibernating bats observed during this study hibernated singularly, with distances of ten to several hundred metres separating them.

Cold bat cartoonBats will select their hibernacula (the place they choose to hibernate in) very carefully according to temperature, moisture and location. Generally, bats will opt for hibernacula where the temperature is around 5 deg-C (41 deg-F). In their 2003 paper for Zoological Science, Professor Ling-Ling Lee and Dr. Ying-Yi Ho of the National Taiwan University report that Formosan Leaf-nosed bats (Hipposideros armiger terasensis) chose hibernacula with lower entrances and ceilings than summer roosts and the hibernacula had relative humidities of almost 100%, which is needed to prevent dehydration. Hibernacula can be hollows in trees, mining shafts, caves or houses. Intriguingly, the adage of “bats in the belfry” -- first coined by Devonshire novelist Eden Phillpotts to denote insanity -- is largely untrue. Bats certainly inhabit churches, frequently causing damage to fabrics, brass plates and bronze ornaments with their excrement, but they seem to prefer the roof or south porch to the colder, drafty and cyclically noisy belfry.

Bats will not necessarily hibernate for the entirety of winter; frequently, bats will wake on mild nights to go and forage for insects.  In their Yakuita bat hibernation study mentioned above, the Russian researchers found that during hibernation, the microbats spent most of the time in a state of numbness, being active for only one or two percent of the time. During the three months that Anufriev and his colleagues observed these bats, they became active for short periods (30 minutes to one hour) 11 times. Spontaneous waking of these bats was associated with a rapid increase in body temperature from 2 deg-C anywhere up to almost 19 deg-C (66 deg-F). This highlights a problem that hibernation poses for bats: waking up requires a substantial amount of energy.  Although the bats in the Russian study awoke 11 times, some bats only store sufficient energy to wake four or five times -- bats must become active periodically to drink and void waste -- making the threat of hibernacula disturbance (most notably by humans) a serious problem.  Waking generally takes about 15 to 20 minutes, although some species can only raise their body temperature by about one deg-C (almost two deg-F) every two minutes, taking an hour or more to become active.

If the weather is poor for several consecutive days, bats will go into a state of torpor. Torpor is a less extreme version of hibernation (without a decrease in body temperature) that is also designed to save energy. There is a noticeable reduction in insect activity during periods of heavy rain and when temperatures drop below about 10 deg-C (50 deg-F); hunting during these periods would cost the bat more energy than it could regain from eating insects. During these periods of poor prey availability the bats will stay in their roosts, reducing their heart rate to between 40 and 80 bpm and oxygen consumption to about one tenth of the active rate. (Back to Menu)

Tawny OwlPredators: There are very few animals that feed exclusively on bats.  The Bat Falcon (Falco rufigularis) of the New World (the Americas) and the Bat Hawk (Machaeramphus alcinus) of Africa and New Guinea appear to be the exceptions to this generalization – although the Bat Falcon will take non-chiropteran prey, the Bat Hawk appears to feed only on bats. In South America bats will eat other bats, and Raccoons (Procyon lotor) in North America are known to eat bats. Similarly, Great Horned Owls (Bubo virginianus) of North, Central and South America will take bats, as will other raptors -- such as the Red-tailed Hawk (Buteo jamaicensis), Swainson’s Hawk (Buteo swainsoni) and Merlin (Falco columbarius) -- Opossums (Didelphis virginiana), snakes and Forest Mice (Apodemus silvaticus). Here in the UK, there are no predators that take exclusively bats. Owls are probably the greatest natural predators of bats in Britain. The UK is home to six native species of owl and, of these, the Tawny (Strix aluco - left) and Barn Owls (Tyto alba) are the most significant predators (Tawny owls taking more bats than Barn owls).  Other British birds that may take the occasional bat are Raptors -- such as the Lesser Kestrel (Falco naumanni), Common Kestrel (F. tinnunuculus), Peregrine Falcon (F. peregrinus), Hobby (F. subbuteo), Sparrow Hawk (Accipiter nisus) and Goshawks (A. gentilis) -- Black-headed Gulls (Larus ridibundus), Herring Gull (L. argentatus), Rook (Corvus frugilegus) and the Carrion Crow (C. corone).  Weasels (Mustela nivalis) and Stoats (M. erminea) are known to take grounded or low roosting bats, and it is possible that foxes (Vulpes vulpes) will take grounded bats, although all accounts I have come across whilst researching this article were anecdotal. It is also possible that snakes take bats in this country. Britain has three native snake species, and one -- the Aesculapian Snake (Elapha longissima) -- that escaped from a zoo in North Wales during the 1980s. The Adder (Vipera berus) and Smooth snake (Coronella austriaca) are large enough to take a bat (as is the Aesculapian snake) although I’m unaware of any such reports making into the scientific literature.

I should point out that above is a list of ‘natural’ bat predators; certainly in the UK -- and I suspect in other parts of the world -- domestic cats (Felis catus) represent a significant peril for British mammals, bats included. In their fascinating (if somewhat lachrymose) 2003 paper for Mammal Review, Michael Woods of the Mammal Society in London and two colleagues – Dr. Robbie McDonald at the Game Conservancy Trust in County Durham and Prof. Stephen Harris at Bristol University – looked at the predation of wildlife by domestic cats in Great Britain.  The researchers found that of 9, 852 small mammals brought home by 986 cats in 816 households between 1st April and 31st August 1997, 22 (0.2%) were bats. Indeed, in his book, Bats, Phil Richardson notes that “the cat is the only mammal likely to be found on rooftops with sufficient skill to snatch a bat out of the air as it flies past”. (Back to Menu)

Habitat: Fruit bats (Pteropididae) are a tropical bat species, frequenting habitats ranging from dense forests and swamps to savannas.  There are even reports of Fruit bats roosting in lofts and caves (e.g.  the Straw-coloured Fruit Bat, Eidolon helvum). The 41 genera and 164 species of Fruit bat are spread throughout the Old World (i.e. Europe, Asia and Africa). Bat species native to the UK and Europe, will inhabit almost every habitat the countries have to offer. Bats are found in cities, farmland, forests, river valleys, arable pasture, grasslands with peripheral woodlands and wooded pond systems. It is common for bats to show a preference for specific habitat types, and many species will make considerable journeys from their roosts to their preferential feeding grounds. For example, the Lesser Horseshoe bat (Rhinolophus hipposideros) inhabits warmer regions in foothills and highlands, showing a preference for partially wooded areas of limestone, while the Daubenton’s bat (Myotis daubentonii) displays a penchant for flat countryside in open woodland and riparian (river) landscapes. The Common Pipistrelle (Pipistrellus pipistrellus), by contrast, is predominantly a house-dwelling species, although it will inhabit almost any habitat type (excluding very exposed regions) and feed over water, along hedgerows and woodland edges, gardens and under streetlights. I would recommend David MacDonald and Priscilla Barrett’s Field Guide to Mammals of Britain and Europe (see Recommended Reading) for a very detailed overview of habitat and recognition for all bat species found in Britain and Europe.

Interestingly, bats can also be found in bird nests! A 1997 paper in Mammal Review, by Martin Schulz at the University of Queensland provided a review of this phenomenon in Australia. Schulz recorded 15 species of bats roosting in the abandoned nests of birds. Schultz concludes that bird nests in Australia provide roosting habitat for four threatened bats (Murina florum, Kerivoula papuensis, Chalinolobus morio and Nyctophilus timoriensis), and may be important to their conservation.  (Back to Menu)

Fruit BatFood and Feeding: On a global scale, bats take a wide variety of food, including fruit, leaves, bark, nectar, pollen, winged insects, beetles, bugs and termites, spiders, small mammals (especially rodents) birds, lizards, amphibians (especially frogs), scorpions, other bats and fish.  Some bats, the notorious Vampire bats, will feed on the blood of mammals and birds.

As their name suggests, Fruit bats (right) are fructivorous, feeding on fruit, berries, leaves and bark, sometimes taking nectar and pollen, and invariably a few insect larvae that dwell on leaves and fruit. These bats often pick the fruit from the tree and return to a ‘feeding roost’ where they will take the fruit into their mouth and crush it between their teeth, tongue and hard palette. They then swallow the juices and soft parts, spitting out some pips and seeds (which will fall to the ground and may germinate) and swallowing others that will be voided in waste at a later date.

Some Fruit bat species (such as the Mexican Long-nosed bat, Leptonycteris nivalis) have a specialized brush on their tongue to help in the collection of nectar. Fruit bats – along with humans, some other primates and guinea pigs – lack the ability to produce ascorbic acid (vitamin C), so this important vitamin must be obtained from their diet.  Intriguingly, in humans, the inability to produce vitamin c -- which most mammals make in their liver and reptiles synthesize in their kidneys -- results from our lack of the enzyme (gulonolactone oxidase) for which we have the corresponding DNA fragment, but it is genetically ‘switched off'!

All British bat species – and 70% of the world’s bats – are insectivorous and/or arachnivorous (eat insects and/or spiders), although microbats elsewhere in the world will eat other prey. UK bats have teeth typical of insectivores: sharp incisors and canines for gripping and biting with cusped cheek teeth to cut and break-up the food. During the summer months, our native bats will emerge shortly after sunset and hunt actively for a few (up to eight) hours, returning to their roosts shortly before dawn. Favoured feeding grounds may be several kilometres from their roosts and some species spread out and hunt in a defined territory. The small size of many microbats means that they have a high surface area to volume ratio and consequently have a high metabolism. In a 1969 paper, Brian McNab at the University of Florida reported basal (resting) metabolic rate for the Greater Spear-nosed bat (Phyllostomus hastatus) as 70.7ml oxygen per hour in an 84g (about 3 ounces) individual. A healthy young adult male human has a basal metabolic rate of about 286mg oxygen per hour per kilogram; doing the conversion mathematics indicates that P. hastatus has a metabolic rate twice that of its human counterpart (almost 560mg oxygen per hour per kg).  Consequently, bats need to obtain copious quantities of food; Common Pipistrelles have been known to take up to 3000 midges during a single feeding bout, equating to the entire colony consuming tens of thousands of insects each summer.

Some bats will tackle prey larger than most fly insects. For example, in the forests of Panama, the Spectral bat (Vampyrum spectrum) will take small mammals (mainly rodents) and the Greater Bulldog bat (Noctilio leporinus) catches and eats fish. Some bat species are even known to feed on their diurnal counterparts, birds, although such phenomena are rare. In a 2001 paper for the Proceeding of the National Academy of Sciences, Carlos Ibanez, Associate Professor of Research at the Donana Biological Station in Spain, and three colleagues report on bat predation of nocturnally migrating birds. The biologists analysed 14,000 faecal pellets of the Greater Noctule (Nyctalus lasiopterus) and report that this species catches and eats large numbers of migrating Passerines. Passerines are a group containing almost half the world’s bird species, passerines are often referred to as “perching birds” and include sparrows, thrushes, flycatchers, robins and starlings. Ibanez and his team found that while insect remains were found in the bats’ fecal pellets all year round, there were two seasonal peaks in the appearance of feathers that corresponded to major bird migrations (i.e.  March to May and again from August to November). In Spain, Noctules (Nyctalus lasiopterus) will catch and "process" Robins (Erithacus rubecula) in flight.

The question of how the bats catch these birds is still something of an enigma. However, netting of Noctules in the La Rioja region of northern Spain during Ibanez et al.’s study, recovered two freshly severed passerine wings -- later identified as belonging to a Robin and Wood Warbler (Phylloscopus sibilatrix) -- along with a Greater Noctule holding Robin feathers in its claws. Such findings suggest that these bats catch and eat birds in flight, in a similar manner to the “aerial-hawking” seen in bats that catch and eat insects ‘on the wing’.

Vampire bat skeletonPerhaps the most notorious feeding method seen in the Chiroptera is that of sanguivory, or blood-drinking. The taxonomy of this, often maligned, group of bats is still a matter of some debate; although most people now agree that vampire bats actually belong in a subfamily (Desmodontinae) of the Phyllostomidae (the American Leaf-nosed Bats), some maintain that the differences between the leaf-nosed and vampire bats are sufficient to justify them a familial rank (Desmodontidae).  Whoever you choose to believe – and based on work by Professor Robert Baker of the Texas Tech University and Prof. Rodney Honeycutt of the Texas AandM University, I believe that the vampire bats belong in the Desmodontinae – the one thing that is clear is that there are three species of “true” vampire bat: the Common Vampire (Desmodus rotundus), Hairy-legged Vampire (Diphylla ecuadata) and the White-winged Vampire (Diaemus youngi). Vampire bats are native to the Americas, from Mexico to Brazil, Chile and Argentina and, contrary to popular misconception, have never been found in Transylvania! Although vampire bats were known in popular mythology long before the arrival of the Irish novelist Bram Stoker’s Dracula in 1897, it was perhaps the idea that Count Dracula could morph into a large “vampire bat”, quite capable of exsanguinating (draining the blood from) your average human, that immortalised vampire bats in our psyche. As is so often the case with popular mythology, vampire bats don’t actually live up to their folklore reputation. Not only do vampire bats not actually “suck” blood – instead they make a small cut and lap up the trickling blood – they are also pretty small critters. For example, a mature Common Vampire bat has a wingspan of only 35 to 40 cm (14 – 16 in), is seven to nine centimetres (about 3.5 in) long and weighs in at between 15 and 50g (0.5 to about 2 ounces).  Moreover, reports of vampire bats feeding on humans are very rare; vampires generally opt for livestock (horses, cows, pigs etc. - below, right), with the Hairy-legged vampire showing a penchant for wild and domestic fowl. Indeed, Diphylla generally bites the legs and cloacal (the cavity in the pelvic region through which waste is voided) region of its avian (bird) prey, especially chickens. (Photo: Skeleton of a Vampire bat, Desmodus rotundus, mounted by the photographer.)

Vampire bats have three infrared pit organs in their nasal sac, which have a heat-sensing function and help them gauge the best place to cut.  Experiments by Professor Uwe Schmidt at the University of Bonn in Germany and a colleague in 1985 found that the heat-sensing organs of Desmodus rotundus are sufficiently sensitive to detect human skin from at least 13cm (5 in) away. Once the cut has been made with their razor-sharp teeth, the bat laps at the slow trickle of blood, consuming about 30ml (2 tablespoons) while the donor continues to sleep. Bat saliva is known to contain an anticoagulant -- termed “Draculin” by Venezuelan biochemist Ana Fernandez and her co-workers in their 1999 paper in Biochimica et Biophysica Acta -- which prevents the blood from clotting while the bat feeds. According to Lyudmila Zavalova at the Russian Academy of Science and her colleagues, the anticoagulants of “bloodsuckers” work to prevent an enzyme (thrombin) from reacting with protein (fribrinogen) dissolved in the blood plasma and turning it into an insoluble protein (fibrin) that forms a ‘net’ over the cut and traps blood cells (i.e. a blood clot).

There are also five species of False Vampire bat (family Megadermatidae) from Africa, Asia and Australia, four of which bite the necks of seized rodents, but don’t actually appear to drink the victim’s blood. In their 1976 paper, Ronald Pine of the Field Museum in Chicago and his colleague listed several anecdotal reports that suggest other phyllostomids (American Leaf-nosed bats) – excluding the true vampires – occasionally feed on blood. (Back to Menu)

Baby batBreeding Biology: Like all mammals, bats practice internal fertilization and give birth to live young. In Fruit bats, females don’t reach maturity until they are about two years old – although they are actually capable of reproducing at 18 months – and can have either a single, or multiple oestrus cycles (i.e. come into season) per breeding season, depending on species. A report published by the Lubee Foundation for the American Zoo and Aquarium Association Bat Taxon Advisory Group (AZA BatTAG) in North America back in 1995 documented a possible case of sperm storage by a female Indian Flying Fox (Pteropus giganteus) who became pregnant nine months after having been moved to a single sex enclosure. Depending on species, Fruit bats gestate for anywhere between 105 and 210 days (3.5 to 7 months) following a series of matings through February into March and peaking in April. Alternatively, the bats may copulate in the autumn and give birth in the spring, or copulate in June or July and delay implantation until November so that births occur the following spring. Courtship may involve wing-flicking and vocalization that, if successful, will lead to a brief mating period with a quick ejaculation. It should be pointed out that Fruit bats exhibit terrific variation in their mating and birth times according to species. For example, Straw-coloured Fruit bats (Eidolon helvum) in Uganda and Siberia mate between April and June, delaying implantation such that the young are born some eight-or-more months later, between February and March, to coincide with the rainy seasons. Conversely, the Egyptian Fruit bat (Rosettus aegyptiacus) mates between June and September and young are born between October and December. AZA BatTAG provides a detailed description of the moment of birth and I would recommend a visit to their site if you’re interested in reading more.  Suffice to say, during the birth – which may last from a couple of minutes to a couple of hours – the female will hang upside down by her thumbs and strain hard. The mother closes her wings to protect her newborn from falling and the infant then clings to its mother and is guided to the nearest available nipple. Unlike most bats, Fruit bats are born with fur and some will have their eyes open immediately after birth, those that aren’t usually open their eyes within two weeks.  Dependent on species, the young will be weaned within four months. (Photo: Baby pipistrelle bat.)

Microbats exhibit a somewhat different reproductive itinerary to that seen in their megabat relatives, although, as before, times of courtship, mating and parturition vary according to species. According to Phil Richardson in his book Bats, having aroused from hibernation, male bats are “keen to mate with any bat of the same species”. Indeed, a single male microbat may mate with as many as 30 females; mating generally takes place in the autumn. Females will often store the sperm for several months – in his 1995 book, Bats of the British Isles, A. A. Wardhaugh notes that sperm may be stored in the uteri over the hibernation period, until the spring when the female will produce ova and fertilization can take place. Gestation in microbats is variable and related to ambient temperature (females become torpid under cold conditions and development of the embryo slows down) and the size of the bat (the larger the bat, the longer the gestation). Ergo, gestation can vary from one to eight months with a single pup (twins are rare) born in June or July. Tropical bats may produce two litters per year, although one is the ‘norm’. At birth the pup may be as much as one-quarter the weight of the mother and is altrical (naked, blind and totally dependent on its mother); as with megabats, the female gives birth whilst hanging upside down and will create a ‘safety net’ with her wings or tail membrane to prevent the infant falling. Young are left in a crèche while the females move off to hunt; the mother can detect the high-pitched squeak of her baby amongst the cacophony of noise upon her return. Microbat young are usually weaned within about three weeks and begin their flight preparations shortly afterwards (about August). Vampire bats tend to be the exception, gestating for up to eight months and producing a pup that will be airborne after about four months. Young are usually independent of their mother by late summer and must feed well (often increasing their body weight by more than one-third) if they are to lay down sufficient energy reserves to hibernate. Most British bat species won’t become sexually mature until they are two years old.

Brown bat with pupAs I have already mentioned, the timings of the various mating components vary according to the species in question, but to give an idea of the cycle it is probably easiest to look at one of Britain’s most prolific bat species, the Common Pipistrelle (Pipistrellus pipistrellus). In this species, mating occurs from August to late-November, and hereafter sperm is stored in the uterus until April, when ovulation and subsequent fertilization occurs. Births tend to be around June to mid-July, although occasionally pups are born as late as August if weather conditions are favourable. The newborn pup will weigh only one or two grams and will have its eyes closed for the first three to five days. The neonate is fed solely on milk from its mother until it is about six weeks old, after which it can forage for itself. Most British bats seem to follow a similar sequence. Our resident bats will generally begin to establish a breeding/mating roost during April and May and the number of females in these colonies can range from about 15 in the Seroine (Eptesicus serotinus) to 200 in the Naterer’s bat (Myotis nattereri). (Photo: A Big Brown bat, Eptesicus fuscus, mother with her pup on her right.)

Intriguingly, the presence of a clinging infant doesn’t appear to hamper the mother's activity. In a fascinating study in the journal Behavioural Processes in 1998, Dr. Johnson Balasingh of the Madurai Kamaraj University in India and four colleagues studied the birth and mother-infant relationship of the Indian False Vampire bat (Megaderma lyra). According to Balasingh and his co-workers, the ability of nursing mothers to get about and find food seemed unaffected by their babies, which clung to their mothers continuously for a week after birth.  Balasingh et al.’s study also found that nursing females had two distinct bouts of foraging: one immediately following emergence from the roost at dusk and another during their return to the main roost in the pre-dawn hours. (Back to Menu)

Behaviour and Social Structure: Bats are very social mammals, and it is difficult to do justice to a topic as broad as this without writing reams and reams of text. As such, I will cover bat behaviour and social structure briefly here and urge anyone interested in finding out more to check out the Recommended Reading page for a list of excellent bat books.

Bats are often renowned for forming huge colonies. In his book Bats, Phil Richardson gives the record for most bats in a single roost as being held by the Mexican Free-tailed bat (Tadarida brasiliensis) with an estimated 50 million individuals during the 1960s. Although the numbers of this bat have declined significantly over the last few decades, roosts can still be found in the U.S. containing some 5 million bats. Roosting in such large numbers probably provides some protection from predators and the all-important social interaction that mammals and many other species seem to appreciate. Bats also tend to opt for roosts in some of the most inaccessible places – the reason for this is probably a reflection of how bat hands have evolved into wings. Wings provide little defence against predators and – although bats have sharp claws, these cannot be used for kicking or scratching while the bat is resting – thus bats choose roosts that are as difficult as possible for predators to access. This inaccessibility of roost choice seems limited to the microbats; Fruit bats can often be seen hanging from trees during the day in camps of some 200,000 individuals. According to former English Nature Conservancy Councillor and now bat worker James Robertson’s 1990 book The Complete Bat, it is the females that gather to form these large colonies, with males remaining largely solitary or in small groups until the breeding season. This is certainly true for Common Pipistrelles, males of which live a solitary existence, creating and defending mating territories during the breeding season, which the females will visit briefly from August to November. Indeed, certain species (e.g. the Hoary bat, Lasiurus cinereus and Silver-haired bat, Lasionycteris noctivagans) spend much of their time either solitarily or in small groups, coming together only during the mating season.

Long-eared batLittle Brown bat roost
Sociality in bats can depend on species. Long-eared bat (Plecotus auritus - left) males tend to be either solitary or hang around in small groups, while Little Brown bat (Myotis lucifugus - right) females form large aggregations in cave systems.

Scent plays an important role in the establishment and maintenance of territories and colonies. Bats have scent glands around their throat (called “Gular glands”) and toes, which are used to mark themselves and members of their colony. In the case of the male Gambian Epauletted bat (Epomophorus gambianus) of Africa, large white tufts of fur on his shoulders are used to shower a female with his scents. Organs or cavities used for the storage and display of odours are called Propatagial Sacs. Sac-Winged bats (Saccopteryx, Saccolaimus and Taphozous), found from Africa to South Asia and Australia, use small propatagial sacs located near their shoulders to collect and ferment secretions from their genital region and gular gland, mixing it with urine and saliva – this scent is probably used to attract females. Male White-lined Sac-winged bats (Saccopteryx bilineata) fan the scent from their propatagial sacs onto roosting bats during a complex hovering display. Perhaps the most pungent chiropteran odour is that of male Fishing bats (Noctilo spp.) found throughout New World (western Hemisphere) tropical and subtropical lowland regions. So pungent is this odour that you can apparently smell the bats as they fly past. The scent comes from bacteria living on a fatty acid secretion in propatagial sacs under the bats’ arms; it seems that females find this repugnant odour ravishing!

Serotine batVocalization is important for socialising bats – calls have been associated with general social communication and conveyance of threat.  In a fascinating study published in the Journal of Zoology in September 2003, Guido Pfalzer and Jurgen Kusch at the University of Kaiserslautern in Germany studied the sounds and social calls of 16 European bat species. Pfalzer and Kusch identified 50 distinct call types, some of which appeared to have similar functions in different species. The researchers also found that the ‘aggressive’ calls varied the least between bats, while the more complex mating calls and isolation calls (used for mother-infant interaction) were very diverse. Communication sounds are well documented in most (if not all) species of European bat.  For example, the Common Pipistrelle (Pipistrellus pipistrellus) is well documented to chatter very noisily immediately prior to their emergence from the roost to hunt. Male Pipistrelles also emit a loud ‘holler’ at between 18 and 35 kHz during mating flights. By contrast to the noisy chatter of the Common Pipistrelles, a “sharp whisper” is heard from bat boxes and roosts of the Nathusius’ Pipistrelle (P. nathusii) in Europe.  Another species found in Europe, the Serotines (Eptesicus serotinus - right) engage in active squeaking at roosts, emitting a loud, high-pitched chirping or "tsicking" when alarmed.

As its name suggests, the Natterer’s Bat (Myotis nattereri) also emits sounds – deep chirps and squeaks when roosting, deep humming if alarmed and a high pitched “shrill” during flight. While many bats produce a wide variety of sounds according to their activity and ambience, not all bats are so talkative. The Daubenton’s bat (Myotis daubentonii) doesn’t call whilst in flight and has only occasionally been observed to chirp in roosts.

Vampire bats are amongst the most sociable of the chiropterans.  Indeed, the extremely rare phenomenon of reciprocity -- the idea that favours are done and returned at a later date -- is currently known in only a handful of organisms, vampires being one such group. In vampires this reciprocity is blood-sharing. Gerald Wilkinson at the University of Maryland has demonstrated that for a colony of 200 Common Vampire bats (Desmodus rotundus) in Costa Rica, blood meals are difficult to obtain and as many as 33% of young bats may fail to feed on any given night; feeding success is apparently linked to age, with only 7% of adults failing to feed. The rapid metabolism of bats makes failing to feed for several consecutive nights potentially fatal – in the case of vampire bats, starvation can occur after only three nights without a meal. As such, successful vampire bats will regurgitate blood to feed other members of their colony. However, these sanguivorous microbats are often selective with whom in their group they will feed – generally mates and direct relatives get priority. Most interestingly, these bats seem able to spot freeloaders (i.e. those that never go out to feed because it’s easier to sit in the cave and wait for someone to bring dinner to you) and refuse to feed them. Mothers will regurgitate blood for their pups and supplement the diet of their newborn with blood shortly after birth and periodically during their first year. As with other bats, vampires may travel long distances in search of food and appear to have a homing ability related to their “familiar area”. In a 2000 paper for the International Journal of Mammalian Biology, Horacio Delpietro and a colleague tested the homing ability of 446 Common Vampire bats, releasing them at various distances from their roosts.  Delpietro and Russo found that males were better at finding their way home than females (23% and 8% homing performance, respectively), while females tended to settle in the site of their release – I’ll sidestep the issue of females and reading maps! The researchers concluded that the ability of these bats to find their way home was strongly related to whether they were released within the familiar settings peripheral to their roosts.

A later paper by Delpietro and Russo in the journal Mammal Biology looked at the social structure of vampire bats in captivity. It seems that under captive conditions these bats form a “principal colony” (mainly females and their young, with a few males interspersed for good measure). Interestingly, non-resident males (those outside the principal colony) were accepted into the principal colony when it got cold, suggesting social thermoregulation (i.e. the bats group together to share body heat). The paper also documents females suckling young of other females if they lost their own young. (Back to Menu)

Noctule batInteraction with Humans: In many respects, bats fall into the same maligned and misunderstood category as so many other creatures with which we share this planet: spiders, sharks, snakes, jellyfish and such.  For many people, bats also fall into that ever familiar “Ewwww….get it away, get it away!” order. In the sempiternally funny Ace Venture II: When Nature Calls, Jack Bernstein’s character Ace Venutra Pet Detective (played by Jim Carey) says of bats: “They’re hideous! Lifeless beady eyes, clawed feet, huge grotesque wings. Even fangs! They give you rabies, you know?” Whilst in the caves just outside a village in the Bonai Province, Nambia searching for clues to the disappearance of “Shikaka” (a sacred white bat), Ace confronts bats in a cave with: “Take that you winged spawn of Satan!” and “Die, devil bird!”. While Ace Venture is obviously only a movie (and now cartoon) character, he does sum up some of the innate phobias many people seem to hold of bats.  Indeed, bats form a considerable part of human mythology. (Photo: Noctule bat, Nyctalus noctula.)

In one Eastern tradition it is believed that bats were once birds who prayed to be men – their prayers were only half-answered, leaving them with the faces, teeth and hair of men but the wings of birds. It is said that the bats fly at night to avoid being seen and mocked by birds.  There are also various dictums about bats flying into your hair and bat droppings leading to baldness. However, not all traditions fear bats.  For example, in China, the word for bat is “fu”, meaning happiness.

Regardless of your personal feelings towards bats, they serve an important function in the ecosystems of the world, and are even an important food source for some people (e.g. tribes in Borneo catch, cook and eat Fruit bats). Perhaps the most important function these enigmatic mammals serve is in Chiropterophily, the act of plant pollination and seed distribution by bats.

In their 2003 paper for the journal Biotropica, Robert Hodgkison at the University of Aberdeen and three co-workers assessed the seed dispersers and pollinators of a lowland Rain Forest in Malaysia.  Hodgkison and his team found that more than 13.7% percent of trees in their survey area were at least partially dependent on Fruit bats for pollination and/or seed dispersal. The biologists also note that the distance seeds get dispersed is dependent on the size of the seed and species of bat. Smaller seeds tend to get greater distances from the parent tree before being deposited because small seeds are consumed and take time to work through the digestive system of the bat. Larger seeds are dropped closer to the parent trees because the bats discard the seeds during feeding and, thus, the seeds only make it as far as the nearest feeding perch or roost.

Similarly, Marco Tschapka at the University of Ulm in Germany found that the Understorey Palm (Calyptryogyne ghiesbreghtiana) has evolved to offer bats fruit-like flower tissue as a reward for the bat visiting it.  Most fascinating of all, in his 2003 paper in the Biological Journal of the Linnean Society, Tschapka reports that the palm has actually adapted the positioning of its fruit to increase the likelihood of pollination.  It seems that fruit set (i.e. amount of fruit tissue) was significantly lower in inflorences (flower-bearing stalks) that were visited only by hovering bats, suggesting that the palm gets better pollination possibilities when the bats perch on it. Video evidence bore out Tschapka’s conclusion, showing that during the entire visit, perching bats maintained close body contact with the inflorence, crawling over it and tearing off flowers, while hovering bats merely tore off a flower and flew away with it in their mouth. It is remarkable to think that this palm has evolved to grow fruits that not only attract bats, but are also located in positions sufficiently difficult to access so that the bats must land on the plant and crawl along (making them pick up more pollen than they would were they hovering around the plant).

As I have mentioned in the feeding section of this article, microbats take a considerable number of insects each year and, as such, these critters represent significant (and free) insecticides. In some countries their droppings are also of significant economic importance, being used to make fertilizers and, in some tribes, pots and plates. In the case of droppings collected from a colony of bats roosting at Fanny’s Lodge in Ireland, two ounces (about 60g) applied to a potato patch gave double the yield of the control patch (without bat poo).  Chemical analysis of the droppings revealed that they were 13% nitrogen, 11% phosophorous and 3.5 % potassium – as any gardener will tell you, these elements are essential to the growth and metabolism of most plants.

Eastern pipistrelleOf the 900-or-so species of bat known to science, it is perhaps the Vampires that have the worst reputation and instill the most fear. This is not totally unjustified, because vampire bats do occasionally bite humans. The first account of a vampire bat biting a human was probably the encounter documented by Spanish historian Gonzalo Fernansex de Oviedo in his A Natural History of the West Indies in 1526; de Oviedo reports that the bat would return to feed on the same man during successive nights, despite the presence of other potential victims. More recently, Robert Matthews describes the case of an apparent siege of vampire bat attacks that occurred in the small town of Apora in northeast Bahia, Brazil during July 1991. In his book, Nightmares of Nature, Matthews states that casualties of this rare invasion included a six month old baby -- who was bitten repeatedly on the head, nose, arms and legs by a “swarm” of vampire bats -- and a 12 year old girl. The baby was given five rabies shots that saved her life, but unfortunately the 12-year-old girl (Marisa dos Santos) died of rabies after four weeks in hospital. It transpired later that the attacks had coincided with intensive logging in nearby forests. Indeed, vampire attacks on humans are generally associated with removal of livestock or habitat destruction. It should be noted that, although possible, contraction of rabies from a bat bite is extremely rare. (Photo: Eastern pipistrelle, Pipistrellus subflavus.)

According to Professor of Forensic Medicine at Dundee University Derrick Pounder’s communication to the British Medical Journal in April 2003, “in the United Kingdom classic rabies was eliminated from the animal reservoir in the 1920s, and the 20 or so deaths reported since then resulted from infection acquired overseas”. Indeed, there have only been two confirmed cases of rabies in Daubenton's bats from the UK: one from Newhaven in 1996 and the other in Lancashire during September 2002. In both cases, bat workers handled the bats which later turned out to be infected with rabies - neither worker contracted the disease. This is in stark contrast to mainland Europe, which recorded some 600 cases of infection with bat rabies between 1977 and 2000.  Despite these recent incidences, the UK is still considered rabies free, because bat rabies -- which exists in two distinct forms: European Bat Lyssavirus (EBLV) 1 and 2 --- is genetically distinct from the “classic” rabies carried by foxes, dogs, cats etc. It seems that the main reservoir for EBLV 1 and 2 is the Pond bat (Myotis dasycneme) of Europe and the Daubenton’s bat (Myotis daubentonii), respectively. Dr. Dilip Nathwani at the Ninewells Hospital and Medical School in Dundee and his colleagues report on the third case of bat rabies in the UK -- and the first death -- from EBVL, in their brief communication to Clinical Infectious Diseases. According to Nathwani et al., the victim (a 55 year old male bat worker) was admitted to their hospital suffering from shoulder pain, upper limb paresthesia and tightness, 19 weeks after being bitten by a Daubenton’s bat. Tragically, the gentleman’s condition worsened, leading to his death several weeks later. Analysis on the bat by DEFRA (formally MAFF) was not possible, because the specimen was not retained. Rabies from bats is known in several countries, including Australia, America and Brazil. In their short communication to The Veterinary Record, Dr. Roehe and four colleagues report on the first case of cat rabies (caused by a suspected vampire bat bite) in their region of Brazil for 11 years. The paper notes that although reports of vampire bat bites on cattle are ubiquitous, the incidence of cattle rabies in southern Brazil is very low.

Bat being cared forBat being cared for
Fortunately, there are hundreds of groups and individuals worldwide that dedicate their time and funds to helping rescue and rehabilitate bats. These groups also play an important role in educating people about bats and breaking down some of the informational dogma surrounding them. Left: Feeding a Pipistrelle Pup using a paintbrush. Right: Trying to tempt an injured Long-eared Bat with a larvae.

Hoary batBats are in decline across the globe as a result of our domestic cats, our expansion of housing resulting in habitat loss and our intensification of farming practices. Bats also suffer mortality at the hands of some manmade structures. For example, Gregory Johnson and his colleagues studied the impact of large-scale wind farms on bats at Buffalo Ridge in Minnesota. Their results, published in American Midland Naturalist during 2003, showed that Hoary (Lasiurus cinereus - left) and Eastern Red bats (L. borealis) comprised most of the fatalities, and that the number of bat fatalities increased as the wind farm development proceeded. Johnson et al. also found that the timing of the mortalities suggest that victims were migrant, rather than resident breeding, bats.

Fortunately, there is a growing appreciation for the importance of chiropterans and many organizations are now in place to oversee the treatment of bats. Moreover, the law protects all British bats, making it is an offence to harm a bat or disturb its roost – roost disturbance seems of particular importance, because in his 1935 communication to the Irish Naturalist’s Journal, J.E. Flynn reported that, once disturbed, Lesser Horseshoe bats (Rhinolophus hipposideros) evidently never return to the same place. It is also illegal to keep bats without a license.  These measures, combined with the work of volunteer groups and scientists worldwide to erect bat boxes, monitor bat populations and care for and rehabilitate injured bats is leading to the disbanding of many common bat misconceptions. Hopefully, with misapprehensions gone, people will start treating bats with the respect and admiration worthy of their 50 million years of evolution. (Back to Menu)

Questions and Answers:
What is echolocation and how do bats use it?
How is moth evolution linked to bat echolocation?
What bat species are found in the UK?
What is the "Pipistrelle Split"?
Is the expression 'Blind as a bat' justified?
What should I do if I find and injured bat?
What is hibernation?

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