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= Bat =
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Introduction
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Bats are mammals of the order Chiroptera. With their forelimbs adapted
as wings, they are the only mammals capable of true and sustained
flight. Bats are more manoeuvrable than birds, flying with their very
long spread-out digits covered with a thin membrane or patagium. The
smallest bat, and arguably the smallest extant mammal, is Kitti's
hog-nosed bat, which is 29 - in length, 150 mm across the wings and 2
- in mass. The largest bats are the flying foxes and the giant
golden-crowned flying fox, 'Acerodon jubatus', which can weigh 1.6 kg
and have a wingspan of 1.7 m.
The second largest order of mammals after rodents, bats comprise about
20% of all classified mammal species worldwide, with over 1,400
species. These were traditionally divided into two suborders: the
largely fruit-eating megabats, and the echolocating microbats. But
more recent evidence has supported dividing the order into
Yinpterochiroptera and Yangochiroptera, with megabats as members of
the former along with several species of microbats. Many bats are
insectivores, and most of the rest are frugivores (fruit-eaters) or
nectarivores (nectar-eaters). A few species feed on animals other than
insects; for example, the vampire bats feed on blood. Most bats are
nocturnal, and many roost in caves or other refuges; it is uncertain
whether bats have these behaviours to escape predators. Bats are
present throughout the world, with the exception of extremely cold
regions. They are important in their ecosystems for pollinating
flowers and dispersing seeds; many tropical plants depend entirely on
bats for these services.
Bats provide humans with some direct benefits, at the cost of some
disadvantages. On the benefits side, bat dung has been and in many
places still is mined as guano from caves and used as fertiliser. Bats
consume insect pests, reducing the need for pesticides and other
insect management measures. They are sometimes numerous enough and
close enough to human settlements to serve as tourist attractions, and
they are used as food across Asia and the Pacific Rim. On the
disadvantages side, fruit bats are frequently considered a pest by
fruit growers. Due to their physiology, bats are one type of animal
that acts as a natural reservoir of many pathogens, such as rabies;
and since they are highly mobile, social, and long-lived, they can
readily spread disease among themselves. If humans interact with bats,
these traits become potentially dangerous to humans.
Depending on the culture, bats may be symbolically associated with
positive traits, such as protection from certain diseases or risks,
rebirth, or long life, but in the West, bats are popularly associated
with the superhero Batman, darkness, malevolence, witchcraft,
vampires, and death.
Etymology
======================================================================
An older English name for bats is flittermouse, which matches their
name in other Germanic languages (for example German 'Fledermaus' and
Swedish 'fladdermus'), related to the fluttering of wings. Middle
English had 'bakke', most likely cognate with Old Swedish 'natbakka'
("night-bat"), which may have undergone a shift from '-k-' to '-t-'
(to Modern English 'bat') influenced by Latin 'blatta', "moth,
nocturnal insect". The word "bat" was probably first used in the early
1570s. The name "Chiroptera" derives from 'cheir', "hand" and
πτερόν'pteron', "wing".
Evolution
===========
The delicate skeletons of bats do not fossilise well; it is estimated
that only 12% of bat genera that lived have been found in the fossil
record. Most of the oldest known bat fossils were already very similar
to modern microbats, such as 'Archaeopteropus' (32 million years ago).
The extinct bats 'Palaeochiropteryx tupaiodon' (48 million years ago)
and 'Hassianycteris kumari' (55 million years ago) are the first
fossil mammals whose colouration has been discovered: both were
reddish-brown.
Bats were formerly grouped in the superorder Archonta, along with the
treeshrews (Scandentia), colugos (Dermoptera), and primates. Modern
genetic evidence now places bats in the superorder Laurasiatheria,
with its sister taxon as Fereuungulata, which includes carnivorans,
pangolins, odd-toed ungulates, even-toed ungulates, and cetaceans. One
study places Chiroptera as a sister taxon to odd-toed ungulates
(Perissodactyla).
{{cladogram|align=left|style=width:800px;font-size:85%;line-height:75%|caption=Phylogenetic
tree showing Chiroptera within Laurasiatheria, with Fereuungulata as
its sister taxon according to a 2013 study
|cladogram={{clade
|label1=Boreoeutheria
|1={{clade
|1=Euarchontoglires (primates, treeshrews, rodents, rabbits) 50px
|label2=Laurasiatheria
|2={{clade
|1= Eulipotyphla (hedgehogs, shrews, moles, solenodons)
|label2=Scrotifera
|2={{clade
|1= Chiroptera (bats)
|label2=Fereuungulata
|2=
}}
}}
}}
}}
}}
The phylogenetic relationships of the different groups of bats have
been the subject of much debate. The traditional subdivision into
Megachiroptera and Microchiroptera reflected the view that these
groups of bats had evolved independently of each other for a long
time, from a common ancestor already capable of flight. This
hypothesis recognised differences between microbats and megabats and
acknowledged that flight has evolved only once in mammals. Most
molecular biological evidence supports the view that bats form a
natural or monophyletic group.
{{cladogram|align=left|style=width:700px;font-size:85%;line-height:75%|caption=Internal
relationships of the Chiroptera, divided into the traditional megabat
and microbat clades, according to a 2011 study
|cladogram={{clade
|label1=Chiroptera
|1={{clade
|1=
|2={{clade
|label1=Microchiroptera
|1={{clade
|1={{clade
|label1=Rhinolophoidea
|1={{clade
|1=Megadermatidae (false vampire bats) 60px
|2=
}}
}}
|2={{clade
|label1=Yangochiroptera
|1={{clade
|1={{clade
|1={{clade
|1=
|2={{clade
|1={{clade
|1=
|2={{clade
|1=
|3=Phyllostomidae (New World leaf-nosed bats) 50px
}}
}}
}}
|3={{clade
|1=
|2=
}}
}}
}}
}}
}}
}}
}}
}}
}}
}}
Genetic evidence indicates that megabats originated during the early
Eocene, and belong within the four major lines of microbats. Two new
suborders have been proposed; Yinpterochiroptera includes the
Pteropodidae, or megabat family, as well as the families
Rhinolophidae, Hipposideridae, Craseonycteridae, Megadermatidae, and
Rhinopomatidae. Yangochiroptera includes the other families of bats
(all of which use laryngeal echolocation), a conclusion supported by a
2005 DNA study. A 2013 phylogenomic study supported the two new
proposed suborders.
{{cladogram|align=left|style=width:700px;font-size:85%;line-height:75%|caption=Internal
relationships of the Chiroptera, with the megabats subsumed within
Yinpterochiroptera, according to a 2013 study
|cladogram={{clade
|label1=Chiroptera
|1={{clade
|1={{clade
|1=Yangochiroptera (as above) 60px
|2={{clade
|label1=Yinpterochiroptera
|1={{clade
|1=Pteropodidae (megabats) 40px
|2=
}}
}}
}}
}}
}}
}}
In the 1980s, a hypothesis based on morphological evidence stated the
Megachiroptera evolved flight separately from the Microchiroptera. The
flying primate hypothesis proposed that, when adaptations to flight
are removed, the Megachiroptera are allied to primates by anatomical
features not shared with Microchiroptera. For example, the brains of
megabats have advanced characteristics. Although recent genetic
studies strongly support the monophyly of bats, debate continues about
the meaning of the genetic and morphological evidence.
The 2003 discovery of an early fossil bat from the 52-million-year-old
Green River Formation, 'Onychonycteris finneyi', indicates that flight
evolved before echolocative abilities. 'Onychonycteris' had claws on
all five of its fingers, whereas modern bats have at most two claws on
two digits of each hand. It also had longer hind legs and shorter
forearms, similar to climbing mammals that hang under branches, such
as sloths and gibbons. This palm-sized bat had short, broad wings,
suggesting that it could not fly as fast or as far as later bat
species. Instead of flapping its wings continuously while flying,
'Onychonycteris' probably alternated between flaps and glides in the
air. This suggests that this bat did not fly as much as modern bats,
but flew from tree to tree and spent most of its time climbing or
hanging on branches. The distinctive features of the 'Onychonycteris'
fossil also support the hypothesis that mammalian flight most likely
evolved in arboreal locomotors, rather than terrestrial runners. This
model of flight development, commonly known as the "trees-down"
theory, holds that bats first flew by taking advantage of height and
gravity to drop down on to prey, rather than running fast enough for a
ground-level take off.
The molecular phylogeny was controversial, as it pointed to microbats
not having a unique common ancestry, which implied that some seemingly
unlikely transformations occurred. The first is that laryngeal
echolocation evolved twice in bats, once in Yangochiroptera and once
in the rhinolophoids. The second is that laryngeal echolocation had a
single origin in Chiroptera, was subsequently lost in the family
Pteropodidae (all megabats), and later evolved as a system of
tongue-clicking in the genus 'Rousettus'. Analyses of the sequence of
the vocalization gene 'FoxP2' were inconclusive on whether laryngeal
echolocation was lost in the pteropodids or gained in the echolocating
lineages. Echolocation probably first derived in bats from
communicative calls. The Eocene bats 'Icaronycteris' (52 million years
ago) and 'Palaeochiropteryx' had cranial adaptations suggesting an
ability to detect ultrasound. This may have been used at first mainly
to forage on the ground for insects and map out their surroundings in
their gliding phase, or for communicative purposes. After the
adaptation of flight was established, it may have been refined to
target flying prey by echolocation. Bats may have evolved echolocation
through a shared common ancestor, in which case it was then lost in
the Old World megabats, only to be regained in the horseshoe bats; or,
echolocation evolved independently in both the Yinpterochiroptera and
Yangochiroptera lineages. Analyses of the hearing gene 'Prestin' seem
to favour the idea that echolocation developed independently at least
twice, rather than being lost secondarily in the pteropodids, but
ontogenic analysis of the cochlea supports that laryngeal echolocation
evolved only once.
Classification
================
Bats are placental mammals. After rodents, they are the largest order,
making up about 20% of mammal species. In 1758, Carl Linnaeus
classified the seven bat species he knew of in the genus 'Vespertilio'
in the order Primates. Around twenty years later, the German
naturalist Johann Friedrich Blumenbach gave them their own order,
Chiroptera. Since then, the number of described species has risen to
over 1,400, traditionally classified as two suborders: Megachiroptera
(megabats), and Microchiroptera (microbats/echolocating bats). Not all
megabats are larger than microbats. Several characteristics
distinguish the two groups. Microbats use echolocation for navigation
and finding prey, but megabats apart from those in the genus
'Rousettus' do not, relying instead on their eyesight. Accordingly,
megabats have a well-developed visual cortex and good visual acuity.
Megabats have a claw on the second finger of the forelimb. The
external ears of microbats do not close to form a ring; the edges are
separated from each other at the base of the ear. Megabats eat fruit,
nectar, or pollen, while most microbats eat insects; others feed on
fruit, nectar, pollen, fish, frogs, small mammals, or blood.
Below is a table chart following the bat classification of families
recognized by various authors of the ninth volume of 'Handbook of the
Mammals of the World' published in 2019:
|colspan="100%" align="center" bgcolor="#c2c2a9"|**Chiroptera
Blumenbach, 1779**
|colspan="100%" align="center" bgcolor="#d9d9c1"|**Yinpterochiroptera
Springer, Teeling, Madsen, Stanhope & Jong, 2001**
|colspan="100%" align="center" bgcolor="#ebebd2"|**Pteropodoidea J.
E. Gray, 1821**
Family !! English Name !! Number of Species !! Image Figure
|Pteropodidae J. E. Gray, 1821 |Old World fruit bats |191 |100px
|colspan="100%" align="center" bgcolor="#ebebd2"|**Rhinolophoidea J.
E. Gray, 1825**
Family !! English Name !! Number of Species !! Image Figure
|Rhinopomatidae Bonaparte, 1838 |Mouse-tailed bats |6 |100px
|Craseonycteridae Hill, 1974 |Hog-nosed bat |1 |100px
|Megadermatidae H. Allen, 1864 |False-vampires |6 |100px
|Rhinonycteridae J. E. Gray, 1866 |Trident bats |9 |100px
|Hipposideridae Lydekker, 1891 |Old World leaf-nosed bats |88 |100px
|Rhinolophidae J. E. Gray, 1825 |Horseshoe bats |109 |100px
|colspan="100%" align="center" bgcolor="#d9d9c1"|**Yangochiroptera
Koopman, 1984**
|colspan="100%" align="center" bgcolor="#ebebd2"|**Emballonuroidea
Gervais in de Castelnau, 1855**
Family !! English Name !! Number of Species !! Image Figure
|Nycteridae Van der Hoeven, 1855 |Slit-faced bats |15 |100px
|Emballonuridae Gervais in de Castelnau, 1855 |Sheath-tailed bats |54
|100px
|colspan="100%" align="center" bgcolor="#ebebd2"|**Noctilionoidea J.
E. Gray, 1821**
Family !! English Name !! Number of Species !! Image Figure
|Myzopodidae Thomas, 1904 |Madagascar sucker-footed bats |2 |100px
|Mystacinidae Dobson, 1875 |New Zealand short-tailed bats |2 |100px
|Thyropteridae Miller, 1907 |Disk-winged bats |5 |100px
|Furipteridae J. E. Gray, 1866 |Smoky bat and thumbless bat |2 |100px
|Noctilionidae J. E. Gray, 1821 |Bulldog bats |2 |100px
|Mormoopidae Saussure, 1860 |Ghost-faced, naked-backed and mustached
bats |18 |100px
|Phyllostomidae J. E. Gray, 1825 |New World leaf-nosed bats |217
|100px
|colspan="100%" align="center" bgcolor="#ebebd2"|**Vespertilionoidea
J. E. Gray, 1821**
Family !! English Name !! Number of Species !! Image Figure
|Natalidae J. E. Gray, 1825 |Funnel-eared bats |12 |100px
|Molossidae Gervais in de Castelnau, 1855 |Free-tailed bats |126
|100px
|Miniopteridae Dobson, 1875 |Free-tailed bats |38 |100px
|Cistugidae Lack et al., 2010 |Wing-gland bats |2
|Vespertilionidae J. E. Gray, 1821 |Vesper bats |496 |100px
Skull and dentition
=====================
The head and teeth shape of bats can vary by species. In general,
megabats have longer snouts, larger eye sockets and smaller ears,
giving them a more dog-like appearance, which is the source of their
nickname of "flying foxes". Among microbats, longer snouts are
associated with nectar-feeding. while vampire bats have reduced snouts
to accommodate large incisors and canines.
Small insect-eating bats can have as many as 38 teeth, while vampire
bats have only 20. Bats that feed on hard-shelled insects have fewer
but larger teeth with longer canines and more robust lower jaws than
species that prey on softer bodied insects. In nectar-feeding bats,
the canines are long while the cheek-teeth are reduced. In
fruit-eating bats, the cusps of the cheek teeth are adapted for
crushing. The upper incisors of vampire bats lack enamel, which keeps
them razor-sharp. The bite force of small bats is generated through
mechanical advantage, allowing them to bite through the hardened
armour of insects or the skin of fruit.
Wings and flight
==================
Bats are the only mammals capable of sustained flight, as opposed to
gliding, as in the flying squirrel. The fastest bat, the Mexican
free-tailed bat ('Tadarida brasiliensis'), can achieve a ground speed
of 160 km/h.
The finger bones of bats are much more flexible than those of other
mammals, owing to their flattened cross-section and to low levels of
calcium near their tips. The elongation of bat digits, a key feature
required for wing development, is due to the upregulation of bone
morphogenetic proteins (Bmps). During embryonic development, the gene
controlling Bmp signalling, 'Bmp2', is subjected to increased
expression in bat forelimbsresulting in the extension of the manual
digits. This crucial genetic alteration helps create the specialised
limbs required for powered flight. The relative proportion of extant
bat forelimb digits compared with those of Eocene fossil bats have no
significant differences, suggesting that bat wing morphology has been
conserved for over fifty million years. During flight, the bones
undergo bending and shearing stress; the bending stresses felt are
smaller than in terrestrial mammals, but the shearing stress is
larger. The wing bones of bats have a slightly lower breaking stress
point than those of birds.
As in other mammals, and unlike in birds, the radius is the main
component of the forearm. Bats have five elongated digits, which all
radiate around the wrist. The thumb points forward and supports the
leading edge of the wing, and the other digits support the tension
held in the wing membrane. The second and third digits go along the
wing tip, allowing the wing to be pulled forward against aerodynamic
drag, without having to be thick as in pterosaur wings. The fourth and
fifth digits go from the wrist to the trailing edge, and repel the
bending force caused by air pushing up against the stiff membrane. Due
to their flexible joints, bats are more manoeuvrable and more
dexterous than gliding mammals.
The wings of bats are much thinner and consist of more bones than the
wings of birds, allowing bats to manoeuvre more accurately than the
latter, and fly with more lift and less drag. By folding the wings in
toward their bodies on the upstroke, they save 35 percent energy
during flight. The membranes are delicate, tearing easily, but can
regrow, and small tears heal quickly. The surface of the wings is
equipped with touch-sensitive receptors on small bumps called Merkel
cells, also found on human fingertips. These sensitive areas are
different in bats, as each bump has a tiny hair in the centre, making
it even more sensitive and allowing the bat to detect and adapt to
changing airflow; the primary use is to judge the most efficient speed
at which to fly, and possibly also to avoid stalls. Insectivorous bats
may also use tactile hairs to help perform complex manoeuvres to
capture prey in flight.
The patagium is the wing membrane; it is stretched between the arm and
finger bones, and down the side of the body to the hind limbs and
tail. This skin membrane consists of connective tissue, elastic
fibres, nerves, muscles, and blood vessels. The muscles keep the
membrane taut during flight. The extent to which the tail of a bat is
attached to a patagium can vary by species, with some having
completely free tails or even no tails. The skin on the body of the
bat, which has one layer of epidermis and dermis, as well as hair
follicles, sweat glands and a fatty subcutaneous layer, is very
different from the skin of the wing membrane. The patagium is an
extremely thin double layer of epidermis; these layers are separated
by a connective tissue centre, rich with collagen and elastic fibres.
The membrane has no hair follicles or sweat glands, except between the
fingers. For bat embryos, apoptosis (cell death) affects only the
hindlimbs, while the forelimbs retain webbing between the digits that
forms into the wing membranes. Unlike birds, whose stiff wings deliver
bending and torsional stress to the shoulders, bats have a flexible
wing membrane that can resist only tension. To achieve flight, a bat
exerts force inwards at the points where the membrane meets the
skeleton, so that an opposing force balances it on the wing edges
perpendicular to the wing surface. This adaptation does not permit
bats to reduce their wingspans, unlike birds, which can partly fold
their wings in flight, radically reducing the wing span and area for
the upstroke and for gliding. Hence bats cannot travel over long
distances as birds can.
Nectar- and pollen-eating bats can hover, in a similar way to
hummingbirds. The sharp leading edges of the wings can create
vortices, which provide lift. The vortex may be stabilised by the
animal changing its wing curvatures.
Roosting and gaits
====================
When not flying, bats hang upside down from their feet, a posture
known as roosting. The femurs are attached at the hips in a way that
allows them to bend outward and upward in flight. The ankle joint can
flex to allow the trailing edge of the wings to bend downwards. This
does not permit many movements other than hanging or clambering up
trees. Most megabats roost with the head tucked towards the belly,
whereas most microbats roost with the neck curled towards the back.
This difference is reflected in the structure of the cervical or neck
vertebrae in the two groups, which are clearly distinct. Tendons allow
bats to lock their feet closed when hanging from a roost. Muscular
power is needed to let go, but not to grasp a perch or when holding
on.
When on the ground, most bats can only crawl awkwardly. A few species
such as the New Zealand lesser short-tailed bat and the common vampire
bat are agile on the ground. Both species make lateral gaits (the
limbs move one after the other) when moving slowly but vampire bats
move with a bounding gait (all limbs move in unison) at greater
speeds, the folded up wings being used to propel them forward. Vampire
bat likely evolved these gaits to follow their hosts while
short-tailed bats developed in the absence of terrestrial mammal
competitors. Enhanced terrestrial locomotion does not appear to have
reduced their ability to fly.
Internal systems
==================
Bats have an efficient circulatory system. They seem to make use of
particularly strong venomotion, a rhythmic contraction of venous wall
muscles. In most mammals, the walls of the veins provide mainly
passive resistance, maintaining their shape as deoxygenated blood
flows through them, but in bats they appear to actively support blood
flow back to the heart with this pumping action. Since their bodies
are relatively small and lightweight, bats are not at risk of blood
flow rushing to their heads when roosting.
Bats possess a highly adapted respiratory system to cope with the
demands of powered flight, an energetically taxing activity that
requires a large continuous throughput of oxygen. In bats, the
relative alveolar surface area and pulmonary capillary blood volume
are larger than in most other small quadrupedal mammals. During flight
the respiratory cycle has a one-to-one relationship with the wing-beat
cycle. Because of the restraints of the mammalian lungs, bats cannot
maintain high-altitude flight.
It takes a lot of energy and an efficient circulatory system to work
the flight muscles of bats. Energy supply to the muscles engaged in
flight require about double the amount compared to the muscles that do
not use flight as a means of mammalian locomotion. In parallel to
energy consumption, blood oxygen levels of flying animals are twice as
much as those of their terrestrially locomoting mammals. As the blood
supply controls the amount of oxygen supplied throughout the body, the
circulatory system must respond accordingly. Therefore, compared to a
terrestrial mammal of the same relative size, the bat's heart can be
up to three times larger, and pump more blood. Cardiac output is
directly derived from heart rate and stroke volume of the blood; an
active microbat can reach a heart rate of 1000 beats per minute.
With its extremely thin membranous tissue, a bat's wing can
significantly contribute to the organism's total gas exchange
efficiency. Because of the high energy demand of flight, the bat's
body meets those demands by exchanging gas through the patagium of the
wing. When the bat has its wings spread it allows for an increase in
surface area to volume ratio. The surface area of the wings is about
85% of the total body surface area, suggesting the possibility of a
useful degree of gas exchange. The subcutaneous vessels in the
membrane lie very close to the surface and allow for the diffusion of
oxygen and carbon dioxide.
The digestive system of bats has varying adaptations depending on the
species of bat and its diet. As in other flying animals, food is
processed quickly and effectively to keep up with the energy demand.
Insectivorous bats may have certain digestive enzymes to better
process insects, such as chitinase to break down chitin, which is a
large component of insects. Vampire bats, probably due to their diet
of blood, are the only vertebrates that do not have the enzyme
maltase, which breaks down malt sugar, in their intestinal tract.
Nectivorous and frugivorous bats have more maltase and sucrase enzymes
than insectivorous, to cope with the higher sugar contents of their
diet.
The adaptations of the kidneys of bats vary with their diets.
Carnivorous and vampire bats consume large amounts of protein and can
output concentrated urine; their kidneys have a thin cortex and long
renal papillae. Frugivorous bats lack that ability and have kidneys
adapted for electrolyte-retention due to their low-electrolyte diet;
their kidneys accordingly have a thick cortex and very short conical
papillae. Bats have higher metabolic rates associated with flying,
which lead to an increased respiratory water loss. Their large wings
are composed of the highly vascularized membranes, increasing the
surface area, and leading to cutaneous evaporative water loss. Water
helps maintain their ionic balance in their blood, thermoregulation
system, and removal of wastes and toxins from the body via urine. They
are also susceptible to blood urea poisoning if they do not receive
enough fluid.
The structure of the uterine system in female bats can vary by
species, with some having two uterine horns while others have a single
mainline chamber.
Echolocation
==============
Microbats and a few megabats emit ultrasonic sounds to produce echoes.
Sound intensity of these echos are dependent on subglottic pressure.
The bats’ cricothyroid muscle controls the orientation pulse
frequency, which is an important function. This muscle is located
inside the larynx and it is the only tensor muscle capable of aiding
phonation. By comparing the outgoing pulse with the returning echoes,
the brain and auditory nervous system can produce detailed images of
the bat's surroundings. This allows bats to detect, localise, and
classify their prey in darkness. Bat calls are some of the loudest
airborne animal sounds, and can range in intensity from 60 to 140
decibels. Microbats use their larynx to create ultrasound, and emit it
through the mouth and sometimes the nose. The latter is most
pronounced in the horseshoe bats ('Rhinolophus' spp.). Microbat calls
range in frequency from 14,000 to well over 100,000 Hz, extending well
beyond the range of human hearing (between 20 and 20,000 Hz). Various
groups of bats have evolved fleshy extensions around and above the
nostrils, known as nose-leaves, which play a role in sound
transmission.
In low-duty cycle echolocation, bats can separate their calls and
returning echoes by time. They have to time their short calls to
finish before echoes return. Bats contract their middle ear muscles
when emitting a call, so they can avoid deafening themselves. The time
interval between the call and echo allows them to relax these muscles,
so they can hear the returning echo. The delay of the returning echoes
allows the bat to estimate the range to their prey.
In high-duty cycle echolocation, bats emit a continuous call and
separate pulse and echo in frequency. The ears of these bats are
sharply tuned to a specific frequency range. They emit calls outside
this range to avoid deafening themselves. They then receive echoes
back at the finely tuned frequency range by taking advantage of the
Doppler shift of their motion in flight. The Doppler shift of the
returning echoes yields information relating to the motion and
location of the bat's prey. These bats must deal with changes in the
Doppler shift due to changes in their flight speed. They have adapted
to change their pulse emission frequency in relation to their flight
speed so echoes still return in the optimal hearing range.
In addition to echolocating prey, bat ears are sensitive to the
fluttering of moth wings, the sounds produced by tymbalate insects,
and the movement of ground-dwelling prey, such as centipedes and
earwigs. The complex geometry of ridges on the inner surface of bat
ears helps to sharply focus echolocation signals, and to passively
listen for any other sound produced by the prey. These ridges can be
regarded as the acoustic equivalent of a Fresnel lens, and exist in a
large variety of unrelated animals, such as the aye-aye, lesser
galago, bat-eared fox, mouse lemur, and others. Bats can estimate the
elevation of their target using the interference patterns from the
echoes reflecting from the tragus, a flap of skin in the external ear.
By repeated scanning, bats can mentally construct an accurate image of
the environment in which they are moving and of their prey. Some
species of moth have exploited this, such as the tiger moths, which
produces aposematic ultrasound signals to warn bats that they are
chemically protected and therefore distasteful. Moth species including
the tiger moth can produce signals to jam bat echolocation. Many moth
species have a hearing organ called a tympanum, which responds to an
incoming bat signal by causing the moth's flight muscles to twitch
erratically, sending the moth into random evasive manoeuvres.
Vision
========
The eyes of most microbat species are small and poorly developed,
leading to poor visual acuity, but no species is blind. Most microbats
have mesopic vision, meaning that they can detect light only in low
levels, whereas other mammals have photopic vision, which allows
colour vision. Microbats may use their vision for orientation and
while travelling between their roosting grounds and feeding grounds,
as echolocation is effective only over short distances. Some species
can detect ultraviolet (UV). As the bodies of some microbats have
distinct coloration, they may be able to discriminate colours.
Megabat species often have eyesight as good as, if not better than,
human vision. Their eyesight is adapted to both night and daylight
vision, including some colour vision.
Magnetoreception
==================
Microbats make use of magnetoreception, in that they have a high
sensitivity to the Earth's magnetic field, as birds do. Microbats use
a polarity-based compass, meaning that they differentiate north from
south, unlike birds, which use the strength of the magnetic field to
differentiate latitudes, which may be used in long-distance travel.
The mechanism is unknown but may involve magnetite particles.
Thermoregulation
==================
Most bats are homeothermic (having a stable body temperature), the
exception being the vesper bats (Vespertilionidae), the horseshoe bats
(Rhinolophidae), the free-tailed bats (Molossidae), and the
bent-winged bats (Miniopteridae), which extensively use heterothermy
(where body temperature can vary). Compared to other mammals, bats
have a high thermal conductivity. The wings are filled with blood
vessels, and lose body heat when extended. At rest, they may wrap
their wings around themselves to trap a layer of warm air. Smaller
bats generally have a higher metabolic rate than larger bats, and so
need to consume more food in order to maintain homeothermy.
Bats may avoid flying during the day to prevent overheating in the
sun, since their dark wing-membranes absorb solar radiation. Bats may
not be able to dissipate heat if the ambient temperature is too high;
they use saliva to cool themselves in extreme conditions. Among
megabats, the flying fox 'Pteropus hypomelanus' uses saliva and
wing-fanning to cool itself while roosting during the hottest part of
the day. Among microbats, the Yuma myotis ('Myotis yumanensis'), the
Mexican free-tailed bat, and the pallid bat ('Antrozous pallidus')
cope with temperatures up to by panting, salivating, and licking
their fur to promote evaporative cooling; this is sufficient to
dissipate twice their metabolic heat production.
Bats also possess a system of sphincter valves on the arterial side of
the vascular network that runs along the edge of their wings. When
fully open, these allow oxygenated blood to flow through the capillary
network across the wing membrane; when contracted, they shunt flow
directly to the veins, bypassing the wing capillaries. This allows
bats to control how much heat is exchanged through the flight
membrane, allowing them to release heat during flight. Many other
mammals use the capillary network in oversized ears for the same
purpose.
Torpor
========
Torpor, a state of decreased activity where the body temperature and
metabolism decreases, is especially useful for microbats, as they use
a large amount of energy while active, depend upon an unreliable food
source, and have a limited ability to store fat. They generally drop
their body temperature in this state to 6 -, and may reduce their
energy expenditure by 50 to 99%. Around 97% of all microbats use
torpor. Tropical bats may use it to avoid predation, by reducing the
amount of time spent on foraging and thus reducing the chance of being
caught by a predator. Megabats were generally believed to be
homeothermic, but three species of small megabats, with a mass of
about 50 g, have been known to use torpor: the common blossom bat
('Syconycteris australis'), the long-tongued nectar bat ('Macroglossus
minimus'), and the eastern tube-nosed bat ('Nyctimene robinsoni').
Torpid states last longer in the summer for megabats than in the
winter.
During hibernation, bats enter a torpid state and decrease their body
temperature for 99.6% of their hibernation period; even during periods
of arousal, when they return their body temperature to normal, they
sometimes enter a shallow torpid state, known as "heterothermic
arousal". Some bats become dormant during higher temperatures to keep
cool in the summer months.
Heterothermic bats during long migrations may fly at night and go into
a torpid state roosting in the daytime. Unlike migratory birds, which
fly during the day and feed during the night, nocturnal bats have a
conflict between travelling and eating. The energy saved reduces their
need to feed, and also decreases the duration of migration, which may
prevent them from spending too much time in unfamiliar places, and
decrease predation. In some species, pregnant individuals may not use
torpor.
Size
======
The smallest bat is Kitti's hog-nosed bat ('Craseonycteris
thonglongyai'), which is 29 - long with a 150 mm wingspan and weighs 2
-. It is also arguably the smallest extant species of mammal, next to
the Etruscan shrew. The largest bats are a few species of 'Pteropus'
megabats and the giant golden-crowned flying fox, ('Acerodon
jubatus'), which can weigh 1.6 kg with a wingspan of 1.7 m. Larger
bats tend to use lower frequencies and smaller bats higher for
echolocation; high-frequency echolocation is better at detecting
smaller prey. Small prey may be absent in the diets of large bats as
they are unable to detect them. The adaptations of a particular bat
species can directly influence what kinds of prey are available to it.
Ecology
======================================================================
Flight has enabled bats to become one of the most widely distributed
groups of mammals. Apart from the high Arctic, the Antarctic and a few
isolated oceanic islands, bats exist in almost every habitat on Earth.
Tropical areas tend to have more species than temperate ones.
Different species select different habitats during different seasons,
ranging from seasides to mountains and deserts, but they require
suitable roosts. Bat roosts can be found in hollows, crevices,
foliage, and even human-made structures, and include "tents" the bats
construct with leaves. Megabats generally roost in trees. Most
microbats are nocturnal and megabats are typically diurnal or
crepuscular. Microbats are known to exhibit diurnal behaviour in
temperate regions during summer when there is insufficient night time
to forage, and in areas where there are few avian predators during the
day.
In temperate areas, some microbats migrate hundreds of kilometres to
winter hibernation dens; others pass into torpor in cold weather,
rousing and feeding when warm weather allows insects to be active.
Others retreat to caves for winter and hibernate for as much as six
months. Microbats rarely fly in rain; it interferes with their
echolocation, and they are unable to hunt.
Food and feeding
==================
Different bat species have different diets, including insects, nectar,
pollen, fruit and even vertebrates. Megabats are mostly fruit, nectar
and pollen eaters. Due to their small size, high-metabolism and rapid
burning of energy through flight, bats must consume large amounts of
food for their size. Insectivorous bats may eat over 120 percent of
their body weight, while frugivorous bats may eat over twice their
weight. They can travel significant distances each night,
exceptionally as much as 38.5 km in the spotted bat ('Euderma
maculatum'), in search of food. Bats use a variety of hunting
strategies. Bats get most of their water from the food they eat; many
species also drink from water sources like lakes and streams, flying
over the surface and dipping their tongues into the water.
The Chiroptera as a whole are in the process of losing the ability to
synthesise vitamin C. In a test of 34 bat species from six major
families, including major insect- and fruit-eating bat families, all
were found to have lost the ability to synthesise it, and this loss
may derive from a common bat ancestor, as a single mutation. At least
two species of bat, the frugivorous bat ('Rousettus leschenaultii')
and the insectivorous bat ('Hipposideros armiger'), have retained
their ability to produce vitamin C.
Insects
=========
Most microbats, especially in temperate areas, prey on insects. The
diet of an insectivorous bat may span many species, including flies,
mosquitos, beetles, moths, grasshoppers, crickets, termites, bees,
wasps, mayflies and caddisflies. Large numbers of Mexican free-tailed
bats ('Tadarida brasiliensis') fly hundreds of metres above the ground
in central Texas to feed on migrating moths. Species that hunt insects
in flight, like the little brown bat ('Myotis lucifugus'), may catch
an insect in mid-air with the mouth, and eat it in the air or use
their tail membranes or wings to scoop up the insect and carry it to
the mouth. The bat may also take the insect back to its roost and eat
it there. Slower moving bat species, such as the brown long-eared bat
('Plecotus auritus') and many horseshoe bat species, may take or glean
insects from vegetation or hunt them from perches. Insectivorous bats
living at high latitudes have to consume prey with higher energetic
value than tropical bats.
Fruit and nectar
==================
Fruit eating, or frugivory, is found in both major suborders. Bats
prefer ripe fruit, pulling it off the trees with their teeth. They fly
back to their roosts to eat the fruit, sucking out the juice and
spitting the seeds and pulp out onto the ground. This helps disperse
the seeds of these fruit trees, which may take root and grow where the
bats have left them, and many species of plants depend on bats for
seed dispersal. The Jamaican fruit bat ('Artibeus jamaicensis') has
been recorded carrying fruits weighing 3 - or even as much as 50 g.
Nectar-eating bats have acquired specialised adaptations. These bats
possess long muzzles and long, extensible tongues covered in fine
bristles that aid them in feeding on particular flowers and plants.
The tube-lipped nectar bat ('Anoura fistulata') has the longest tongue
of any mammal relative to its body size. This is beneficial to them in
terms of pollination and feeding. Their long, narrow tongues can reach
deep into the long cup shape of some flowers. When the tongue
retracts, it coils up inside the rib cage. Because of these features,
nectar-feeding bats cannot easily turn to other food sources in times
of scarcity, making them more prone to extinction than other types of
bat. Nectar feeding also aids a variety of plants, since these bats
serve as pollinators, as pollen gets attached to their fur while they
are feeding. Around 500 species of flowering plant rely on bat
pollination and thus tend to open their flowers at night. Many
rainforest plants depend on bat pollination.
Vertebrates
=============
Some bats prey on other vertebrates, such as fish, frogs, lizards,
birds and mammals. The fringe-lipped bat ('Trachops cirrhosus,') for
example, is skilled at catching frogs. These bats locate large groups
of frogs by tracking their mating calls, then plucking them from the
surface of the water with their sharp canine teeth. The greater
noctule bat can catch birds in flight. Some species, like the greater
bulldog bat ('Noctilio leporinus') hunt fish. They use echolocation to
detect small ripples on the water's surface, swoop down and use
specially enlarged claws on their hind feet to grab the fish, then
take their prey to a feeding roost and consume it. At least two
species of bat are known to feed on other bats: the spectral bat
('Vampyrum spectrum'), and the ghost bat ('Macroderma gigas').
Blood
=======
A few species, specifically the common, white-winged, and hairy-legged
vampire bats, feed only on animal blood (hematophagy). The common
vampire bat typically feeds on large mammals such as cattle; the
hairy-legged and white-winged vampires feed on birds. Vampire bats
target sleeping prey and can detect deep breathing. Heat sensors in
the nose help them to detect blood vessels near the surface of the
skin. They pierce the animal's skin with their teeth, biting away a
small flap, and lap up the blood with their tongues, which have
lateral grooves adapted to this purpose. The blood is kept from
clotting by an anticoagulant in the saliva.
Predators, parasites, and diseases
====================================
Bats are subject to predation from birds of prey, such as owls, hawks,
and falcons, and at roosts from terrestrial predators able to climb,
such as cats. Low-flying bats are vulnerable to crocodiles. Twenty
species of tropical New World snakes are known to capture bats, often
waiting at the entrances of refuges, such as caves, for bats to fly
past. J. Rydell and J. R. Speakman argue that bats evolved
nocturnality during the early and middle Eocene period to avoid
predators. The evidence is thought by some zoologists to be equivocal
so far.
Among ectoparasites, bats carry fleas and mites, as well as specific
parasites such as bat bugs and bat flies (Nycteribiidae and
Streblidae). Bats are among the few non-aquatic mammalian orders that
do not host lice, possibly due to competition from more specialised
parasites that occupy the same niche.
White nose syndrome is a condition associated with the deaths of
millions of bats in the Eastern United States and Canada. The disease
is named after a white fungus, 'Pseudogymnoascus destructans', found
growing on the muzzles, ears, and wings of afflicted bats. The fungus
is mostly spread from bat to bat, and causes the disease. The fungus
was first discovered in central New York State in 2006 and spread
quickly to the entire Eastern US north of Florida; mortality rates of
90-100% have been observed in most affected caves. New England and the
mid-Atlantic states have, since 2006, witnessed entire species
completely extirpated and others with numbers that have gone from the
hundreds of thousands, even millions, to a few hundred or less. Nova
Scotia, Quebec, Ontario, and New Brunswick have witnessed identical
die offs, with the Canadian government making preparations to protect
all remaining bat populations in its territory. Scientific evidence
suggests that longer winters where the fungus has a longer period to
infect bats result in greater mortality. In 2014, the infection
crossed the Mississippi River, and in 2017, it was found on bats in
Texas.
Bats are natural reservoirs for a large number of zoonotic pathogens,
including rabies, endemic in many bat populations, histoplasmosis both
directly and in guano, Nipah and Hendra viruses, and possibly the
ebola virus, whose natural reservoir is yet unknown. Their high
mobility, broad distribution, long life spans, substantial sympatry
(range overlap) of species, and social behaviour make bats favourable
hosts and vectors of disease. Reviews have found different answers as
to whether bats have more zoonotic viruses than other mammal groups.
One 2015 review found that bats, rodents, and primates all harbored
significantly more zoonotic viruses (which can be transmitted to
humans) than other mammal groups, though the differences among the
aforementioned three groups were not significant (bats have no more
zoonotic viruses than rodents and primates). Another 2020 review of
mammals and birds found that the identify of the taxonomic groups did
not have any impact on the probability of harboring zoonotic viruses.
Instead, more diverse groups had greater viral diversity.
They seem to be highly resistant to many of the pathogens they carry,
suggesting a degree of adaptation to their immune systems. Their
interactions with livestock and pets, including predation by vampire
bats, accidental encounters, and the scavenging of bat carcasses,
compound the risk of zoonotic transmission. Bats are implicated in the
emergence of severe acute respiratory syndrome (SARS) in China, since
they serve as natural hosts for coronaviruses, several from a single
cave in Yunnan, one of which developed into the SARS virus. However,
they neither cause nor spread COVID-19.
Social structure
==================
Some bats lead solitary lives, while others live in colonies of more
than a million. Living in large colonies lessens the risk to an
individual of predation. For instance, the Mexican free-tailed bat fly
for more than one thousand miles to the 100-foot wide cave known as
Bracken Cave every March to October which plays home to an astonishing
twenty million of the species, whereas a mouse-eared bat lives an
almost completely solitary life.
Temperate bat species may swarm at hibernation sites as autumn
approaches. This may serve to introduce young to hibernation sites,
signal reproduction in adults and allow adults to breed with those
from other groups.
Several species have a fission-fusion social structure, where large
numbers of bats congregate in one roosting area, along with breaking
up and mixing of subgroups. Within these societies, bats are able to
maintain long-term relationships. Some of these relationships consist
of matrilineally related females and their dependent offspring. Food
sharing and mutual grooming may occur in certain species, such as the
common vampire bat ('Desmodus rotundus'), and these strengthen social
bonds.
Communication
===============
Bats are among the most vocal of mammals and produce calls to attract
mates, find roost partners and defend resources. These calls are
typically low-frequency and can travel long distances. Mexican
free-tailed bats are one of the few species to "sing" like birds.
Males sing to attract females. Songs have three phrases: chirps,
trills and buzzes, the former having "A" and "B" syllables. Bat songs
are highly stereotypical but with variation in syllable number, phrase
order, and phrase repetitions between individuals. Among greater
spear-nosed bats ('Phyllostomus hastatus'), females produce loud,
broadband calls among their roost mates to form group cohesion. Calls
differ between roosting groups and may arise from vocal learning.
In a study on captive Egyptian fruit bats, 70% of the directed calls
could be identified by the researchers as to which individual bat made
it, and 60% could be categorised into four contexts: squabbling over
food, jostling over position in their sleeping cluster, protesting
over mating attempts and arguing when perched in close proximity to
each other. The animals made slightly different sounds when
communicating with different individual bats, especially those of the
opposite sex. In the highly sexually dimorphic hammer-headed bat
('Hypsignathus monstrosus'), males produce deep, resonating,
monotonous calls to attract females. Bats in flight make vocal signals
for traffic control. Greater bulldog bats honk when on a collision
course with each other.
Bats also communicate by other means. Male little yellow-shouldered
bats ('Sturnira lilium') have shoulder glands that produce a spicy
odour during the breeding season. Like many other species, they have
hair specialised for retaining and dispersing secretions. Such hair
forms a conspicuous collar around the necks of the some Old World
megabat males. Male greater sac-winged bats ('Saccopteryx bilineata')
have sacs in their wings in which they mix body secretions like saliva
and urine to create a perfume that they sprinkle on roost sites, a
behaviour known as "salting". Salting may be accompanied by singing.
Reproduction and lifecycle
============================
Most bat species are polygynous, where males mate with multiple
females. Male pipistrelle, noctule and vampire bats may claim and
defend resources that attract females, such as roost sites, and mate
with those females. Males unable to claim a site are forced to live on
the periphery where they have less reproductive success. Promiscuity,
where both sexes mate with multiple partners, exists in species like
the Mexican free-tailed bat and the little brown bat. There appears to
be bias towards certain males among females in these bats. In a few
species, such as the yellow-winged bat and spectral bat, adult males
and females form monogamous pairs. Lek mating, where males aggregate
and compete for female choice through display, is rare in bats but
occurs in the hammerheaded bat.
For temperate living bats, mating takes place in late summer and early
autumn. Tropical bats may mate during the dry season. After
copulation, the male may leave behind a mating plug to block the sperm
of other males and thus ensure his paternity. In hibernating species,
males are known to mate with females in torpor. Female bats use a
variety of strategies to control the timing of pregnancy and the birth
of young, to make delivery coincide with maximum food ability and
other ecological factors. Females of some species have delayed
fertilisation, in which sperm is stored in the reproductive tract for
several months after mating. Mating occurs in late summer to early
autumn but fertilisation does not occur until the following late
winter to early spring. Other species exhibit delayed implantation, in
which the egg is fertilised after mating, but remains free in the
reproductive tract until external conditions become favourable for
giving birth and caring for the offspring. In another strategy,
fertilisation and implantation both occur, but development of the
foetus is delayed until good conditions prevail. During the delayed
development the mother keeps the fertilised egg alive with nutrients.
This process can go on for a long period, because of the advanced gas
exchange system.
For temperate living bats, births typically take place in May or June
in the northern hemisphere; births in the southern hemisphere occur in
November and December. Tropical species give birth at the beginning of
the rainy season. In most bat species, females carry and give birth to
a single pup per litter. At birth, a bat pup can be up to 40 percent
of the mother's weight, and the pelvic girdle of the female can expand
during birth as the two halves are connected by a flexible ligament.
Females typically give birth in a head-up or horizontal position,
using gravity to make birthing easier. The young emerges rear-first,
possibly to prevent the wings from getting tangled, and the female
cradles it in her wing and tail membranes. In many species, females
give birth and raise their young in maternity colonies and may assist
each other in birthing.
Most of the care for a young bat comes from the mother. In monogamous
species, the father plays a role. Allo-suckling, where a female
suckles another mother's young, occurs in several species. This may
serve to increase colony size in species where females return to their
natal colony to breed. A young bat's ability to fly coincides with the
development of an adult body and forelimb length. For the little brown
bat, this occurs about eighteen days after birth. Weaning of young for
most species takes place in under eighty days. The common vampire bat
nurses its offspring beyond that and young vampire bats achieve
independence later in life than other species. This is probably due to
the species' blood-based diet, which is difficult to obtain on a
nightly basis.
Life expectancy
=================
The maximum lifespan of bats is three-and-a-half times longer than
other mammals of similar size. Six species have been recorded to live
over thirty years in the wild: the brown long-eared bat ('Plecotus
auritus'), the little brown bat ('Myotis lucifugus'), Brandt's bat
('Myotis brandti'), the lesser mouse-eared bat ('Myotis blythii') the
greater horseshoe bat ('Rhinolophus ferrumequinum'), and the Indian
flying fox ('Pteropus giganteus'). One hypothesis consistent with the
rate-of-living theory links this to the fact that they slow down their
metabolic rate while hibernating; bats that hibernate, on average,
have a longer lifespan than bats that do not. Another hypothesis is
that flying has reduced their mortality rate, which would also be true
for birds and gliding mammals. Bat species that give birth to multiple
pups generally have a shorter lifespan than species that give birth to
only a single pup. Cave-roosting species may have a longer lifespan
than non-roosting species because of the decreased predation in caves.
A male Brandt's bat was recaptured in the wild after 41 years, making
it the oldest known bat.
Conservation<!--linked from [[bat conservation]]-->
=====================================================
Groups such as the Bat Conservation International aim to increase
awareness of bats' ecological roles and the environmental threats they
face. In the United Kingdom, all bats are protected under the Wildlife
and Countryside Acts, and disturbing a bat or its roost can be
punished with a heavy fine.
In Sarawak, Malaysia, "all bats" are protected under the Wildlife
Protection Ordinance 1998, but species such as the hairless bat
('Cheiromeles torquatus') are still eaten by the local communities.
Humans have caused the extinction of several species of bat in modern
history, the most recent being the Christmas Island pipistrelle
('Pipistrellus murrayi'), which was declared extinct in 2009.
Many people put up bat houses to attract bats. The 1991 University of
Florida bat house is the largest occupied artificial roost in the
world, with around 400,000 residents. In Britain, thickwalled and
partly underground World War II pillboxes have been converted to make
roosts for bats, and purpose-built bat houses are occasionally built
to mitigate damage to habitat from road or other developments. Cave
gates are sometimes installed to limit human entry into caves with
sensitive or endangered bat species. The gates are designed not to
limit the airflow, and thus to maintain the cave's micro-ecosystem. Of
the 47 species of bats found in the United States, 35 are known to use
human structures, including buildings and bridges. Fourteen species
use bat houses.
Bats are eaten in countries across Africa, Asia and the Pacific Rim.
In some cases, such as in Guam, flying foxes have become endangered
through being hunted for food. There is evidence that wind turbines
create sufficient barotrauma (pressure damage) to kill bats. Bats have
typical mammalian lungs, which are thought to be more sensitive to
sudden air pressure changes than the lungs of birds, making them more
liable to fatal rupture. Bats may be attracted to turbines, perhaps
seeking roosts, increasing the death rate. Acoustic deterrents may
help to reduce bat mortality at wind farms.
Cultural significance<!--A link to here is in: Animal#In human culture.-->
============================================================================
Since bats are mammals, yet can fly, they are considered to be liminal
beings in various traditions. In many cultures, including in Europe,
bats are associated with darkness, death, witchcraft, and malevolence.
Among Native Americans such as the Creek, Cherokee and Apache, the bat
is identified as a trickster. In Tanzania, a winged batlike creature
known as Popobawa is believed to be a shapeshifting evil spirit that
assaults and sodomises its victims. In Aztec mythology, bats
symbolised the land of the dead, destruction, and decay. An East
Nigerian tale tells that the bat developed its nocturnal habits after
causing the death of his partner, the bush-rat, and now hides by day
to avoid arrest.
More positive depictions of bats exist in some cultures. In China,
bats have been associated with happiness, joy and good fortune. Five
bats are used to symbolise the "Five Blessings": longevity, wealth,
health, love of virtue and peaceful death. The bat is sacred in Tonga
and is often considered the physical manifestation of a separable
soul. In the Zapotec civilisation of Mesoamerica, the bat god presided
over corn and fertility.
The Weird Sisters in Shakespeare's 'Macbeth' used the fur of a bat in
their brew. In Western culture, the bat is often a symbol of the night
and its foreboding nature. The bat is a primary animal associated with
fictional characters of the night, both villainous vampires, such as
Count Dracula and before him 'Varney the Vampire', and heroes, such as
the DC Comics character Batman. Kenneth Oppel's Silverwing novels
narrate the adventures of a young bat, based on the silver-haired bat
of North America.
The bat is sometimes used as a heraldic symbol in Spain and France,
appearing in the coats of arms of the towns of Valencia, Palma de
Mallorca, Fraga, Albacete, and Montchauvet. Three US states have an
official state bat. Texas and Oklahoma are represented by the Mexican
free-tailed bat, while Virginia is represented by the Virginia
big-eared bat ('Corynorhinus townsendii virginianus').
Economics
===========
Insectivorous bats in particular are especially helpful to farmers, as
they control populations of agricultural pests and reduce the need to
use pesticides. It has been estimated that bats save the agricultural
industry of the United States anywhere from $3.7billion to $53billion
per year in pesticides and damage to crops. This also prevents the
overuse of pesticides, which can pollute the surrounding environment,
and may lead to resistance in future generations of insects.
Bat dung, a type of guano, is rich in nitrates and is mined from caves
for use as fertiliser. During the US Civil War, saltpetre was
collected from caves to make gunpowder; it used to be thought that
this was bat guano, but most of the nitrate comes from nitrifying
bacteria.
The Congress Avenue Bridge in Austin, Texas, is the summer home to
North America's largest urban bat colony, an estimated 1,500,000
Mexican free-tailed bats. About 100,000 tourists a year visit the
bridge at twilight to watch the bats leave the roost.
See also
======================================================================