Temporal range: 52–0MaEarly Eocene – Recent
|Townsend's big-eared bat, Corynorhinus townsendii|
|Worldwide distribution of bat species|
Bats are mammals of the order Chiroptera (pron.: / /; from the Greek χείρ - cheir, "hand" and πτερόν - pteron, "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, can only glide for short distances. Bats do not flap their entire forelimbs, as birds do, but instead flap their spread-out digits, which are very long and covered with a thin membrane or patagium.
Bats represent about 20% of all classified mammal species worldwide, with about 1,240 bat species divided into two suborders: the less specialized and largely fruit-eating megabats, or flying foxes, and the more highly specialized and echolocating microbats. About 70% of bats are insectivores. Most of the rest are frugivores, or fruit eaters. A few species, such as the fish-eating bat, feed from animals other than insects, with the vampire bats being hematophagous. Bats are present throughout most of the world, performing vital ecological roles of pollinating flowers and dispersing fruit seeds. Many tropical plant species depend entirely on bats for the distribution of their seeds. Bats are important in eating insect pests, reducing the need for pesticides. The smallest bat is the Kitti's hog-nosed bat, measuring 29–34 mm (1.14–1.34 in) in length, 15 cm (5.91 in) across the wings and 2–2.6 g (0.07–0.09 oz) in mass. It is also arguably the smallest extant species of mammal, with the Etruscan shrew being the other contender. The largest species of bat are a few species of Pteropus and the giant golden-crowned flying fox with a weight up to 1.6 kg (4 lb) and wingspan up to 1.7 m (5 ft 7 in).
Classification and evolution
Bats are mammals. They are often called "flying rodents" or "flying rats". In many languages, the word for "bat" is cognate with the word for "mouse": for example, chauve-souris ("bald-mouse") in French, murciélago ("blind mouse") in Spanish, летучая мышь ("flying mouse") in Russian, slijepi miš ("blind mouse") in Bosnian, nahkhiir ("leather mouse") in Estonian, vlermuis (winged mouse) in Afrikaans, from the Dutch word vleermuis. An older English name for bats is flittermice, which matches their name in other Germanic languages (for example German Fledermaus and Swedish fladdermus). Bats were formerly thought to be most closely related to flying lemurs, treeshrews, and primates, but recent molecular cladistics research indicates that they actually belong to Laurasiatheria, a diverse group also containing Carnivora and Artiodactyla.
The two traditionally recognized suborders of bats are:
- Megachiroptera (megabats)
- Microchiroptera (microbats/echolocating bats)
Not all megabats are larger than microbats. The major distinctions between the two suborders are:
- Microbats use echolocation; megabats do not with the exception of Rousettus and relatives.
- Microbats lack the claw at the second toe of the forelimb.
- The ears of microbats do not close to form a ring; the edges are separated from each other at the base of the ear.
- Microbats lack underfur; they are either naked or have guard hairs.
Megabats eat fruit, nectar or pollen, while most microbats eat insects; others may feed on the blood of animals, small mammals, fish, frogs, fruit, pollen or nectar. Megabats have well-developed visual cortices and show good visual acuity, while microbats rely on echolocation for navigation and finding prey.
The phylogenetic relationships of the different groups of bats have been the subject of much debate. The traditional subdivision between Megachiroptera and Microchiroptera reflects the view that these groups of bats have evolved independently of each other for a long time, from a common ancestor already capable of flight. This hypothesis recognized differences between microbats and megabats and acknowledged that flight has only evolved once in mammals. Most molecular biological evidence supports the view that bats form a single or monophyletic group.
Researchers have proposed alternate views of chiropteran phylogeny and classification, but more research is needed.
In the 1980s, a hypothesis based on morphological evidence was offered that stated the Megachiroptera evolved flight separately from the Microchiroptera. The so-called flying primates theory proposes that when adaptations to flight are removed, the Megachiroptera are allied to primates by anatomical features not shared with Microchiroptera. One example is the brains of megabats show a number of advanced characteristics that link them to primates. Although recent genetic studies support the monophyly of bats, debate continues as to the meaning of available genetic and morphological evidence.
Consequently, two new suborders based on molecular data have been proposed. The new suborder Yinpterochiroptera includes the Pteropodidae or megabat family, as well as the Rhinolophidae, Hipposideridae, Craseonycteridae, Megadermatidae, and Rhinopomatidae families The new suborder Yangochiroptera includes all the remaining families of bats (all of which use laryngeal echolocation). These two new suborders are strongly supported by statistical tests. Teeling (2005) found 100% bootstrap support in all maximum likelihood analyses for the division of Chiroptera into these two modified suborders. This conclusion is further supported by a 15-base-pair deletion in BRCA1 and a seven-base-pair deletion in PLCB4 present in all Yangochiroptera and absent in all Yinpterochiroptera. The chiropteran phylogeny based on molecular evidence is controversial because microbat paraphyly implies one of two seemingly unlikely hypotheses occurred. The first suggests laryngeal echolocation evolved twice in Chiroptera, once in Yangochiroptera and once in the rhinolophoids. The second proposes 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 was inconclusive as to whether laryngeal echolocation was secondarily lost in the pteropodids or independently gained in the echolocating lineages. However, analyses of the "hearing" gene, Prestin seemed to favour the independent gain in echolocating species rather than a secondary loss in the pteropodids.
In addition to Yinpterochiroptera and Yangochiroptera, the names Pteropodiformes and Vespertilioniformes have also been proposed for these suborders. Under this new proposed nomenclature, the suborder Pteropodiformes includes all extant bat families more closely related to the genus Pteropus than the genus Vespertilio, while the suborder Vespertilioniformes includes all extant bat families more closely related to the genus Vespertilio than to the genus Pteropus.
Little fossil evidence is available to help map the evolution of bats, since their small, delicate skeletons do not fossilize very well. However, a Late Cretaceous tooth from South America resembles that of an early microchiropteran bat. Most of the oldest known, definitely identified bat fossils were already very similar to modern microbats. These fossils, Icaronycteris, Archaeonycteris, Palaeochiropteryx and Hassianycteris, are from the early Eocene period, . Archaeopteropus, formerly classified as the earliest known megachiropteran, is now classified as a microchiropteran.
Bats were formerly grouped in the superorder Archonta along with the treeshrews (Scandentia), colugos (Dermoptera), and the primates, because of the apparent similarities between Megachiroptera and such mammals. Genetic studies have now placed bats in the superorder Laurasiatheria along with carnivorans, pangolins, odd-toed ungulates, even-toed ungulates, and cetaceans.
The traditional classification of bats is:
- Order Chiroptera
- Suborder Megachiroptera ( megabats)
- Suborder Microchiroptera ( microbats)
- Superfamily Emballonuroidea
- Emballonuridae ( Sac-winged or sheath-tailed bats)
- Superfamily Molossoidea
- Molossidae ( Free-tailed bats)
- Superfamily Nataloidea
- Furipteridae ( Smoky bats)
- Myzopodidae ( Sucker-footed bats)
- Natalidae ( Funnel-eared bats)
- Thyropteridae ( Disk-winged bats)
- Superfamily Noctilionoidea
- Mormoopidae ( Ghost-faced or moustached bats)
- Mystacinidae ( New Zealand short-tailed bats)
- Noctilionidae ( Bulldog bats or fisherman bats)
- Phyllostomidae ( Leaf-nosed bats)
- Superfamily Rhinolophoidea
- Megadermatidae ( False vampires)
- Nycteridae ( Hollow-faced or slit-faced bats)
- Rhinolophidae ( Horseshoe bats)
- Hipposideridae ( Old World leaf-nosed bats)
- Superfamily Rhinopomatoidea
- Craseonycteridae (Bumblebee bat or Kitti's hog-nosed bat)
- Rhinopomatidae ( Mouse-tailed bats)
- Superfamily Vespertilionoidea
- Vespertilionidae ( Vesper bats or evening bats)
- Antrozoidae ( Pallid Bat and Van Gelder's bat)
- Superfamily Emballonuroidea
- Suborder Megachiroptera ( megabats)
Megabats primarily eat fruit or nectar. In New Guinea, they are likely to have evolved for some time in the absence of microbats. This has resulted in some smaller megabats of the genus Nyctimene becoming (partly) insectivorous to fill the vacant microbat ecological niche. Furthermore, there is some evidence that the fruit bat genus Pteralopex from the Solomon Islands, and its close relative Mirimiri from Fiji, have evolved to fill some niches that were open because there are no nonvolant or non-flying mammals in those islands.
There are few fossilized remains of bats, as they are terrestrial and light-boned. An estimated only 12% of the bat fossil record is complete at the genus level. Fossil remains of an Eocene bat, Icaronycteris, were found in 1960. Another Eocene bat, Onychonycteris finneyi, was found in the 52-million-year-old Green River Formation in Wyoming, United States, in 2003. This intermediate fossil has helped to resolve a long-standing disagreement regarding whether flight or echolocation developed first in bats. It had characteristics indicating it could fly, yet the well-preserved skeleton showed the cochlea of the inner ear lacked development needed to support the greater hearing abilities used by modern echolocating bats. This provided evidence flight in bats developed well before echolocation. The team that found the remains of Onychonycteris finneyi recognized it lacked ear and throat features present not only in echolocating bats today, but also in other known prehistoric species.
The appearance and flight movement of bats 52.5 million years ago were different from those of bats today. Onychonycteris had claws on all five of its fingers, whereas modern bats have at most two claws appearing 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 it could not fly as fast or as far as later bat species. Instead of flapping its wings continuously while flying, Onychonycteris likely alternated between flaps and glides while in the air. Such physical characteristics suggest this bat did not fly as much as modern bats do, rather flying from tree to tree and spending most of its waking day climbing or hanging on the branches of trees.
Flight has enabled bats to become one of the most widely distributed groups of mammals. Apart from the Arctic, the Antarctic and a few isolated oceanic islands, bats exist all over the world. Bats are found in almost every habitat available on Earth. Different species select different habitats during different seasons, ranging from seasides to mountains and even deserts, but bat habitats have two basic requirements: roosts, where they spend the day or hibernate, and places for foraging. Bat roosts can be found in hollows, crevices, foliage, and even human-made structures, and include "tents" the bats construct by biting leaves.
The United States is home to an estimated 45 to 48 species of bats. The three most common species are Myotis lucifugus (little brown bat), Eptesicus fuscus (big brown bat), and Tadarida brasiliensis (Mexican free-tailed bat). The little and the big brown bat are common throughout the northern two-thirds of the country, while the Mexican free-tailed bat is the most common species in the southwest.
Bat echolocation is a perceptual system where ultrasonic sounds are emitted specifically to produce echoes. 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, localize and even classify their prey in complete darkness. At 130 decibels in intensity, bat calls are some of the most intense, airborne animal sounds.
To clearly distinguish returning information, bats must be able to separate their calls from the echoes they receive. Microbats use two distinct approaches.
- Low duty cycle echolocation: Bats can separate their calls and returning echos by time. Bats that use this approach time their short calls to finish before echoes return. This is important because these bats contract their middle ear muscles when emitting a call so they can avoid deafening themselves. The time interval between call and echo allows them to relax these muscles so they can clearly hear the returning echo. The delay of the returning echos provides the bat with the ability to estimate range to their prey.
- 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 of this range to avoid self-deafening. 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 echos 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.
The new Yinpterochiroptera and Yangochiroptera classification of bats, supported by molecular evidence, suggests two possibilities for the evolution of echolocation. It may have been gained once in a common ancestor of all bats and was then subsequently lost in the Old World fruit bats, only to be regained in the horseshoe bats, or echolocation evolved independently in both the Yinpterochiroptera and Yangochiroptera lineages.
Two groups of moths exploit a bat sense to echolocate: tiger moths produce ultrasonic signals to warn the bats they (the moths) are chemically protected or aposematic. This was once thought to be the biological equivalent of " radar jamming", but this theory has yet to be confirmed. The moths Noctuidae 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 maneuvers.
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, earwigs, etc. The complex geometry of ridges on the inner surface of bat ears helps to sharply focus not only echolocation signals, but also 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 may be seen in a large variety of unrelated animals, such as the aye-aye, lesser galago, bat-eared fox, mouse lemur and others.
By repeated scanning, bats can mentally construct an accurate image of the environment in which they are moving or their prey item.
Although the eyes of most microbat species are small and poorly developed, leading to poor visual acuity, none of them are blind. Microbats use vision to navigate, especially for long distances when beyond the range of echolocation. Some species have been shown to be able to detect ultraviolet light. They also have high-quality senses of smell and hearing. Bats hunt at night, reducing competition with birds, and travel large distances of up to 800 km in their search for food.
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 minerals such as calcium near their tips. The skin on their wing membranes has more elasticity, so can stretch much more than other mammals.
The wings of bats are much thinner than those of birds, allowing bats to maneuver more quickly and more accurately than birds. It is also delicate, ripping easily; however, the tissue of the bat's membrane is able to regrow, such that small tears can heal quickly. The surface of their 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 collect information about the air flowing over its wings, and to fly more efficiently by changing the shape of its wings in response. An additional kind of receptor cell is found in the wing membrane of species that use their wings to catch prey. This receptor cell is sensitive to the stretching of the membrane. The cells are concentrated in areas of the membrane where insects hit the wings when the bats capture them.
The teeth of microbats resemble insectivorans. They are very sharp to bite through the hardened armor of insects or the skin of fruit.
Mammals have one-way valves in veins to prevent the blood from flowing backwards, but bats also have one-way valves in arteries.
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 its rib cage.
Most microbats are nocturnal and are active at twilight. A large portion of bats migrate hundreds of kilometres to winter hibernation dens, some pass into torpor in cold weather, rousing and feeding when warm weather allows for insects to be active. Others retreat to caves for winter and hibernate for six months. Bats rarely fly in rain, as the rain interferes with their echo location, and they are unable to locate their food.
The social structure of bats varies, with some bats leading solitary lives and others living in caves colonized by more than a million bats. The fission-fusion social structure is seen among several species of bats. The term "fusion" refers to a large numbers of bats that congregate in one roosting area, and "fission" refers to breaking up and the mixing of subgroups, with individual bats switching roosts with others and often ending up in different trees and with different roostmates.
Studies also show bats make all kinds of sounds to communicate with others. Scientists in the field have listened to bats and have been able to identify some sounds with some behaviour bats will make after the sounds are made.
Some species even prey on vertebrates. The leaf-nosed bats (Phyllostomidae) of Central America and South America, and the two bulldog bat (Noctilionidae) species feed on fish. At least two species of bat are known to feed on other bats: the spectral bat, also known as the American false vampire bat, and the ghost bat of Australia. One species, the greater noctule bat, catches and eats small birds in the air.
Predators of bats include bat hawks and bat falcons.
Most bats have a breeding season, which is in the spring for species living in a temperate climate. Bats may have one to three litters in a season, depending on the species and on environmental conditions, such as the availability of food and roost sites. Females generally have one offspring at a time, which could be a result of the mother's need to fly to feed while pregnant. Female bats nurse their young until they are nearly adult size, because a young bat cannot forage on its own until its wings are fully developed.
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 fertilization, in which sperm are stored in the reproductive tract for several months after mating. In many such cases, mating occurs in the fall, and fertilization does not occur until the following spring. Other species exhibit delayed implantation, in which the egg is fertilized after mating, but remains free in the reproductive tract until external conditions become favorable for giving birth and caring for the offspring.
In yet another strategy, fertilization and implantation both occur, but development of the fetus is delayed until favorable conditions prevail, during the delayed development the mother still gives the fertilized egg nutrients, and oxygenated blood to keep it alive. However this process can go for a long period of time, because of the advanced gas exchange system. All of these adaptations result in the pup being born during a time of high local production of fruit or insects.
At birth, the wings are too small to be used for flight. Young microbats become independent at the age of six to eight weeks, while megabats do not until they are four months old.
A single bat can live over 20 years, but the bat population growth is limited by the slow birth rate.
Hunting, feeding, and drinking
Newborn bats rely on the milk from their mother. When they are a few weeks old, bats are expected to fly and hunt on their own. It is up to them to find and catch their prey, along with satisfying their thirst.
Most bats are nocturnal creatures. Their daylight hours are spent grooming and sleeping; they hunt during the nighttime hours. The means by which bats navigate while finding and catching their prey in the dark was unknown until the 1790s, when Lazzaro Spallanzani conducted a series of experiments on a group of blind bats. These bats were placed in a room in total darkness, with silk threads strung across the room. Even then, the bats were able to navigate their way through the room. Spallanzani concluded the bats were not using their eyes to fly through complete darkness, but something else.
Spallanzani decided the bats were able to catch and find their prey through the use of their ears. To prove this theory, Spallanzani plugged the ears of the bats in his experiment. To his pleasure, he found the bats with plugged ears were not able to fly with the same amount of skill and precision they were able to without their ears plugged.
Bats seem to use their ears to locate and catch their prey, but how they accomplish this was not discovered until the 1930s, by Donald R. Griffin, a biology student at Harvard College at the time. He discovered bats use echolocation to locate and catch their prey. When bats fly, they produce a constant stream of high-pitched sounds only bats are able to hear. When the sound waves produced by these sounds hit an insect or other animal, the echoes bounce back to the bat, and guide them to the source.
Feeding and diet
The majority of food consumed by bats includes insects, fruits and flower nectar, vertebrates and blood. Almost three-fourths of the world’s bats are insect eaters. Insects consumed by bats include both aerial and ground-dwelling insects. Each bat is typically able to consume one-third of its body weight in insects each night, and several hundred insects in a few hours. This means a group of one thousand bats could eat four tons of insects each year. If bats were to become extinct, the insect population is calculated to reach an alarmingly high number.
In a test of 34 bat species from six major families of bats, including major insect- and fruit-eating bat families, bats in all tested families were found to have lost the ability to make vitamin C, and this loss may derive from a common bat ancestor, as a single mutation.
Watching a bat catch and eat an insect is difficult. The action is so fast that all one sees is a bat rapidly change directions, and continue on its way. Scientist Frederick A. Webster discovered how bats catch their prey. In 1960, Webster developed a high-speed camera that was able to take one thousand pictures per second. These photos revealed the fast and precise way in which bats catch insects. Occasionally, a bat will catch an insect in mid-air with its mouth, and eat it in the air. However, more often than not, a bat will use its tail membrane or wings to scoop up the insect and trap it in a sort of "bug net". Then, the bat will take the insect back to its roost. There, the bat will proceed to eat said insect, often using its tail membrane as a kind of napkin, to prevent its meal from falling to the ground.
These bats typically fly down and grasp their prey off the ground with their teeth, and take it to a nearby perch to eat it. Generally, these bats do not use echolocation to locate their prey. Instead, they rely on the sounds produced by the insects. Some make unique sounds, and almost all make some noise while moving through the environment.
Fruits and flower nectar
Fruit eating, or frugivory, is a specific habit found in two families of bats. Megachiropterans and microchiropterans both include species of bat that feed on fruits. These bats feed on the juices of sweet fruits, and fulfill the needs of some seeds to be dispersed. The fruits preferred by most fruit-eating bats are fleshy and sweet, but not particularly strong smelling or colorful. To get the juice of these fruits, bats pull the fruit off the trees with their teeth, and fly back to their roosts with the fruit in their mouths. There, the bats will consume the fruit in a specific way. To do this, the bats crush open the fruit and eat the parts that satisfy their hunger. The remainder of the fruit, the seeds and pulp, are spat onto the ground. These seeds take root and begin to grow into new fruit trees. Over 150 types of plants depend on bats in order to reproduce.
Some bats prefer the nectar of flowers to insects or other animals. These bats have evolved specifically for this purpose. For example, these bats possess long muzzles and long, extensible tongues covered in fine bristles that aid them in feeding on particular flowers and plants. When they sip the nectar from these flowers, pollen gets stuck to their fur, and is dusted off when the bats take flight, thus pollinating the plants below them. The rainforest is said to be the most benefitted of all the biomes where bats live, because of the large variety of appealing plants. Because of their specific eating habits, nectar-feeding bats are more prone to extinction than any other type of bat. However, bats benefit from eating fruits and nectar just as much as from eating insects.
A small group of carnivorous bats feed on other vertebrates and are considered the top carnivores of the bat world. These bats typically eat a variety of animals, but normally consume frogs, lizards, birds, and sometimes other bats. For example, one vertebrate predator, Trachops cirrhosus, is particularly skilled at catching frogs. These bats locate large groups of frogs by distinguishing their mating calls from other sounds around them. They follow the sounds to the source and pluck them from the surface of the water with their sharp canine teeth. Another example is the greater noctule bat, which is believed to catch birds on the wing.
Also, several species of bat feed on fish. These types of bats are found on almost all continents. They use echolocation to detect tiny ripples in the water’s surface to locate fish. From there, the bats swoop down low, inches from the water, and use specially enlarged claws on their hind feet to grab the fish out of the water. The bats then take the fish to a feeding roost and consume the animal.
A few species of bats consume blood exclusively as their diet. This type of diet is referred to as hematophagy, and three species of bats exhibit this behaviour. These species are the common, the white-winged, and the hairy-legged vampire bats. The common vampire bat typically consumes the blood of mammals, while the hairy-legged and white-winged vampires feed on the blood of birds.
Results of eating
To survive hibernation months, some species build up large reserves of body fat, both as fuel and as insulation.
Generally, bats drink water. In 1960, Frederic A. Webster discovered how bats are able to acquire this water. To do this, Webster developed a high-speed camera and flashgun that could take 1000 photos per second. Webster's camera captured the bat's method of skimming the surface of a body of water, and lowering its jaw to get just one drop of water. It then skims again to get a second drop of water, and so on, until it has had its fill of water. Its precision and control is very fine, and it almost never misses. Other, such as the flying fox or fruit bat, gently skim the water's surface, then land nearby to lick water from their chest fur.
Through conservancy efforts of groups such as the Organization for Bat Conservation and Bat Conservation International, bats are becoming better understood and people beginning to understand the crucial role bats play in insect control and pollination.
In the United Kingdom, all bats are protected under the Wildlife and Countryside Acts, and even disturbing a bat or its roost can be punished with a heavy fine.
In Sarawak, Malaysia, bats are protected species under the Wildlife Protection Ordinance 1998 (see Malaysian Wildlife Law). The large naked bat (see Mammals of Borneo) and greater nectar bat are consumed by the local communities.
Bats can be a tourist attraction. 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, which eat an estimated 10,000 to 30,000 pounds of insects each night. An estimated 100,000 tourists per year visit the bridge at twilight to watch the bats leave the roost.
Many people put up bat houses to attract bats just as some put up birdhouses to attract birds. Reasons for this vary, but most centre around the bats being the primary nocturnal insectivores in most, if not all, ecologies. Bat houses can be made from scratch or from kits, or bought ready made. Plans for bat houses exist on many web sites, as well as guidelines for designing a bat house. Some conservation societies give away free bat houses to enthusiasts worldwide.
Constructed in March 1991, the University of Florida bat house is the largest occupied artificial roost in the world. The bat house has an approximated 300,000 insect-eating residents. These bats can eat upwards of 2.5 billion bugs (2,500 pounds or 1,100 kilograms) per night.
A 1987 fire caused a colony of bats residing in Johnson Hall's attic to become homeless. This forced them to move to the James G. Pressly Stadium on the north side of campus. The odour and the guano from this newly arrived colony did not please spectators, thus furthering the movement for a new bat-ordained structure. In September 1991, thousands of bats were captured and transported to the newly built bat house. In the following evenings, these bats flew away, and found new homes. For three years the bat house remained empty. Finally, in 1995, the bats moved in permanently, and the colony continued to grow. The colony grew so much, that in 2009, part of the original bat house collapsed, and a new “Bat Barn” was constructed next to it. Along with that, the interior of the original was rebuilt.
In Britain, British hardened field defences of World War II have been converted to make roosts for bats. Pillboxes that are well dug-in and thick-walled are naturally damp and provide the stable thermal environment required by bats that would otherwise hibernate in caves. With a few minor modifications, suitable pillboxes can be converted to artificial caves for bats.
Again in the UK, purpose-built bat houses are occasionally built when existing roosts are destroyed by developments such as new roads; one such has been built associated with bat bridges on the new (2008) A38 Dobwalls bypass.
While conservation efforts are in place to protect bats, many threats still remain.
White nose syndrome
White nose syndrome is a condition associated with the deaths of more than a million bats in the northeastern United States. The disease is named after a white fungus, Geomyces destructans, found growing on the muzzles, ears, and wings of afflicted bats. This fungus, which can be spread from bat to bat, is the sole cause of the disease. Mortality rates of 90–100% have been observed in some caves. At least six species of hibernating bats are affected, including the endangered Indiana bat. The cause of death in these species is due to two factors. The fungus desiccates the wings of the animal upsetting its hydrostatic balance during hiberation. It loses water more quickly and thus must go out more often to drink and maintain hydration. This drains its energy stores and because of a lack of food in the winter, leaves it either dead or severely emaciated when it emerges from hibernation. Because the affected species have long lifespans, and birth rates of only about one offspring per year, populations are not expected to recover quickly.
Barotrauma and wind turbines
Although sounds or vibrations emitted from wind turbines have no adverse effect on human health, evidence suggests barotrauma is causing bat fatalities around wind farms. The lungs of bats are typical mammalian lungs, and unlike the lungs of birds, they are thought to be more sensitive to sudden air pressure changes in their immediate vicinity, such as near wind turbines, and are more liable to rupture. Bats suffer a higher death rate than birds in the neighbourhood of wind turbines. Since there are no signs of external trauma, the cause has been hypothesized to be a greater sensitivity to sudden pressure fluctuations in the mammalian lung than in that of birds. In addition, it has been suggested that bats are attracted to these structures, perhaps seeking roosts, and thereby increasing the death rate.
Pathogens and role in the transmission of zoonoses
Among ectoparasites, bats occasionally carry fleas, but are one of the few mammalian orders that cannot host lice (most of the others are water animals).
Bats are natural reservoirs for a large number of zoonotic pathogens, including rabies, severe acute respiratory syndrome (SARS), Henipavirus (i.e. Nipah virus and Hendra virus) and possibly ebola virus. Their high mobility, broad distribution, and social behaviour (communal roosting and fission-fusion social structure) make bats favourable hosts and vectors of disease. Many species also appear to have a high tolerance for harbouring pathogens and often do not develop disease while infected. However, contrary to folklore, this is not true of rabies, which is as fatal to bats as it is to all other species. However, a bat may be ill with rabies for a longer time than other mammals.
In regions where rabies is endemic, only 0.5% of bats carry the disease. In the United States, bats typically constitute around a quarter of reported cases of rabies in wild animals. However, their bites account for the vast majority of cases of rabies in humans. Of the 36 cases of domestically-acquired rabies recorded in the country in 1995-2010, two were caused by dog bites and four patients were infected by receiving transplants from an organ donor who had previously died of rabies. All other cases were caused by bat bites. Rabies is considered fully preventable if the patient is administered a vaccine prior to the onset of symptoms. However, unlike raccoon or skunk bites, bat bites may go ignored or unnoticed and hence untreated. Rabid bats are broadly distributed throughout the United States; in 2008-2010, cases were reported in every state except Alaska and Hawaii, and Puerto Rico.
Rabid bats may be clumsy, disoriented, and unable to fly, which makes it more likely they will come into contact with humans. One should avoid handling them or having them in one's living space, as with any wild animal. If a bat is found in living quarters near a child, mentally handicapped person, intoxicated person, sleeping person, or pet, living in an area where rabies is known to occur, the person or pet should receive immediate medical attention for rabies. Bats have very small teeth and can bite a sleeping person without being felt. There is evidence that it is possible for the bat rabies virus to infect victims purely through airborne transmission, without direct physical contact of the victim with the bat itself.
If a bat is found in a house and the possibility of exposure cannot be ruled out, the bat should be sequestered and an animal control officer called immediately, so the bat can be analysed. This also applies if the bat is found dead. If it is certain nobody has been exposed to the bat, it should be removed from the house. The best way to do this with live bats is to close all the doors and windows to the room except one that opens to the outside. The bat should soon leave.
Due to the risk of rabies and to health problems related to their faecal droppings, bats should be excluded from inhabited parts of houses. The Centers for Disease Control and Prevention (CDC) provide fullly detailed information on all aspects of bat management, including how to capture a bat, what to do in case of exposure, and how to bat-proof a house humanely. In certain countries, such as the United Kingdom, it is illegal to handle bats without a license.
Where rabies is not endemic, as throughout most of Western Europe, small bats can be considered harmless. Larger bats can give a nasty bite.
In European cultures, bats have long been associated with witchcraft, black magic and darkness. The witches incorporate bat in their brew in Shakespeare's Macbeth. Because bats are mammals, yet can fly, this gives them status as liminal beings in many cultural traditions.
The bat is sacred in Tonga and is often considered the physical manifestation of a separable soul. Bats are closely associated with vampires, who are said to be able to shapeshift into bats, fog, or wolves. Bats are also symbols of ghosts, death, and disease. Among some Native Americans, such as the Creek, Cherokee and Apache, the bat is a trickster spirit.
Pre-Columbian cultures associated animals with gods, and often displayed them in art. The Moche people depicted bats in their ceramics.
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 villains, such as Dracula, and heroes, such as Batman. The association of the fear of the night with the animal was treated as a literary challenge by Kenneth Oppel, who created a best-selling series of novels, beginning with Silverwing, which feature bats as the central heroic figures much as anthropomorphized rabbits were the central figures to the classic novel Watership Down.
An old wives' tale has it that bats will entangle themselves in people's hair. One likely source of this belief is that insect-eating bats seeking prey may dive erratically toward people, who attract mosquitoes and gnats, leading the squeamish to believe the bats are trying to get in their hair.
In Mesoamerican mythology during the Classic-Contemporary period, bats symbolized the land of the dead, which was considered to be the underworld. They also symbolized destruction and decay. Bats may have symbolized in this way because they fly only at night and dwell in caves during the daytime and are associated with human skulls and bones by classic Maya ceramists. Central Mexicans sometimes depicted bats having snouts that looked like "sacrificial knives and carrying human head" in the Postclassic era. Bat images were engraved onto funerary urns, and were emphasized with large claws and round ears by Zapotecs. They were commonly associated with death. The depiction of bats on funeral urns and goods took on some the characteristics of the jaguar, which was, and still is, another entity of the night and the underworld. There have also been instances where bats are portrayed next to other animals portrayed negatively in Mesoamerica, including scorpions and other nocturnal animals such as owls.
A gigantic, life-size, ceramic bat-man has been discovered and dug up from the Templo Mayor. The Templo Mayor is located in the centre of the Mexica capital of Tenochtitlan. Known as a god of death, this statue has the clawed feet and hands of a bat, but the body of a man. The statue's human-like eyes bulged out from the bat-like head, making the Zapotec images very realistic and living. In the 1930s, the Kaqchikel Maya were said to have proclaimed the bat was the Devil’s provider. Kaqchikel would leave the Devil’s underworld home and collect blood from the animals to be used for scrumptious meals to feed the Devil. “In the myths, the beast of prey and the animal that is preyed upon play two significant roles. They represent two aspects of life—the aggressive, killing, conquering, creating aspect of life, and the one that is the matter or, you might say, the subject matter”. In the Devil’s underworld, dead sinners would work off their sins to get to heaven, indicating the bat, too, was a sinner and worked under the authority of the Devil.
According to Oaxacan mythology, the bat's nocturnal nature can be traced back to its ancient jealousy of birds' feathers. One day, as the myth goes, the bat felt isolated and undesirable, and told God that he was cold. God, fair and just, turned to birds in the animal kingdom and asked if they would show compassion and donate a feather to the bat to help him keep warm. The birds all agreed and began to pluck one feather from their bodies to give to the bat. With all of these feathers, the bat became even more magnificent-looking than all birds, and was able to spread colour to the night sky. During daylight the bat created rainbows that reflected vibrant colors from the sun. With his new beauty and abilities, the bat soon became arrogant and conceited. The birds grew tired of the bat’s self-glorification and decided to fly up to heaven and ask God to do something. When the birds told God of the bat's behaviour, He was surprised and decided to take a look Himself. When on earth, God called on the bat to show him what he was doing. The bat began to fly across the light blue sky where, one by one, each feather began to fall out, uncovering the bat’s natural, ugly-looking body. When all his feathers were gone, the bat became distressed and ashamed of his appearance. He decided to hide in caves during the day and only come out during the night to search for his long-lost feathers.
According to a particular East Nigerian tale, the bat developed its nocturnal habits after causing the death of his partner the bush-rat. The bat and the bush-rat would share activities such as rummaging through the grass and trees, hunting, talking and bonding during the day. When at night, the bat and the bush-rat would alternate in cooking duties, cooking what was caught, and eat together. It appeared to be a dedicated partnership, but the bat hated the bush-rat immensely. The bush-rat always found the bat’s soup more appetising, so when eating dinner one night, asked the bat why the soup tasted better than his own and also asked how it was made. The bat agreed to show him how to make it the next day, but instead was forming a malicious plan.
Next day as bat prepared his soup, the bush-rat came, greeting him and asking if he could be shown what was agreed yesterday. Earlier, the bat has found a pot looking exactly like the one he used usually, but it held warm water and so decided to use this instead. The bat explained to the bush-rat that to make his soup, he had to boil himself prior to serving the soup, where sweetness and flavor of the soup came from the flesh. The bat jumped in the pot seemingly excited, with the bush-rat mesmerised. After a few minutes the bat climbed out and while the bush-rat was distracted, switched pots. The bat then served his soup out of the soup pot, both tasted it. Overanxious and eager, the bush-rat jumped into the pot of warm water. He stayed much longer in the pot, dying in the process.
When the bush-rat’s wife returned that night to find her husband dead, she wept and ran to the chief of the land's house, telling him about what happened and what she was sure what the bat had done. In hearing this, the chief became angry, ordering for the immediate arrest of the bat. It just so happened that the bat was flying over the house and overheard what was just said. He quickly went into hiding high up in a tree. When the chief’s men went looking for the bat, he could not be found. The search to arrest the bat carried on over several days, but he still could not be found. The bat needed to eat, so flew out of hiding every night to hunt for food to escape of being arrested. This, according to Eastern Nigeria mythology, is why bats only fly at night.
The bat is sometimes used as a heraldic symbol. The coats of arms of certain cities in eastern Spain, such as Valencia, Palma de Mallorca and Fraga, have the bat over the shield. Formerly, the Barcelona city coat of arms also had a bat crowning it, but the bat has been removed in the present-day versions.
The heraldic use of the bat in Valencia, Catalonia and the Balearic Islands has its origins in a winged dragon ( vibra or vibria), which featured in King James I of Aragon's helmet or cimera reial. This is the most widely accepted theory, although there is also a legend that says that due to the intervention of a bat, King James was able to win a crucial battle against the Saracens that allowed him to win Valencia for his kingdom.
The use of the bat as a heraldic symbol is prevalent in the territories of the former Crown of Aragon and it is little used elsewhere. However, it can be found in a few places, as in the coats of arms of the city of Albacete, in Spain, as well as the town of Montchauvet (Yvelines), in France.
Certain Spanish football clubs including Valencia CF and Levante UD use bats in their badges.
The Burgee of the Royal Valencia Yacht Club (Reial Club Nàutic de València) displays a bat on a golden field in its centre.
Three U.S. states have an official state bat. Texas and Oklahoma are represented by the Mexican free-tailed bat; Virginia is represented by the Virginia big-eared bat.