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.
 Taxonomy: 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.
 The 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)
 Activity: 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.
 Bat 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.
 Finally, 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.
 Bats 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)
 Predators: 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)
 Food 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’.
 Perhaps 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)
 Breeding 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.
 As 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.
 
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!
 Vocalization 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)
 Interaction 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.
 Of 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.
 
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.
 Bats 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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