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Bat
Temporal range: 52–0Ma

Early Eocene – Recent
Big-eared-townsend-fledermaus.jpg
Townsend's big-eared bat, Corynorhinus townsendii
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Infraclass: Eutheria
Superorder: Laurasiatheria[1]
Order: Chiroptera
Blumenbach, 1779
Suborders
See article
Bat range.png
Worldwide distribution of bat species

Bats are mammals of the order Chiroptera (/kaɪˈrɒptərə/; from the Greek χείρ - cheir, "hand"[2] and πτερόν - pteron, "wing"[3]) 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,[4] which are very long and covered with a thin membrane or patagium.

Bats are the second largest order of mammals (after the rodents), representing 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 highly specialized and echolocating microbats.[5] About 70% of bat species 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, or feeding on blood.

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 economically important, as they consume 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.[6][7] It is also arguably the smallest extant species of mammal, with the Etruscan shrew being the other contender.[8] The largest species of bat are a few species of Pteropus (fruit bats or flying foxes) 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).[9]

Classification and evolution


Giant golden-crowned flying fox, Acerodon jubatus

Bats are mammals. 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, saguzahar ("old mouse") in Basque, 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(from Middle Dutch "winged mouse"). An older English name for bats is flittermouse, which matches their name in other Germanic languages (for example German Fledermaus and Swedish fladdermus).[10] Bats were formerly thought to have been most closely related to the flying lemurs, treeshrews, and primates,[11] but recent molecular cladistics research indicates that they actually belong to Laurasiatheria, a diverse group also containing Carnivora and Artiodactyla.[12][13]

The two traditionally recognized suborders of bats are:
Not all megabats are larger than microbats. The major distinctions between the two suborders are:
Megabats eat fruit, nectar, or pollen. Most microbats eat insects; others may feed on fruit, nectar, pollen, fish, frogs, small mammals, or the blood of animals. 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.[17]

Researchers have proposed alternative 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 that the brains of megabats show a number of advanced characteristics that link them to primates. Although recent genetic studies strongly support the monophyly of bats,[18] debate continues as to the meaning of available genetic and morphological evidence.[19]

Genetic evidence indicates that megabats originated during the early Eocene and should be placed within the four major lines of microbats.[20]

Consequently, two new suborders based on molecular data have been proposed. The new suborder of Yinpterochiroptera includes the Pteropodidae, or megabat family, as well as the Rhinolophidae, Hipposideridae, Craseonycteridae, Megadermatidae, and Rhinopomatidae families[21] The other new suborder, Yangochiroptera, includes all of 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.[21] Perhaps most convincingly, a phylogenomic study by Tsagkogeorga et al (2013) showed that the two new proposed suborders were supported by analyses of thousands of genes.[20]

The chiropteran phylogeny based on molecular evidence is controversial because microbat paraphyly implies that one of two seemingly unlikely hypotheses occurred. The first suggests that laryngeal echolocation evolved twice in Chiroptera, once in Yangochiroptera and once in the rhinolophoids.[22][23] The second proposes 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.[24]

Common pipistrelle, Pipistrellus pipistrellus

Analyses of the sequence of the "vocalization" gene, FoxP2 were inconclusive as to whether laryngeal echolocation was secondarily lost in the pteropodids or independently gained in the echolocating lineages.[25] However, analyses of the "hearing" gene, Prestin seemed to favor the independent gain in echolocating species rather than a secondary loss in the pteropodids.[26]

In addition to Yinpterochiroptera and Yangochiroptera, the names Pteropodiformes and Vespertilioniformes have also been proposed for these suborders.[27][28] 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, 52.5 million years ago.[17] 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.[1] A recent study by Zhang et al. places Chiroptera as a sister taxon to the clade Perissodactyla (which includes horses and other odd-toed ungulates).[29] However, the first phylogenomic analysis of bats shows that bats are not sister to Perissodactyla, and instead are sister to a larger group including ungulates and carnivores.[20]

   Laurasiatheria   

 Eulipotyphla

   Scrotifera   

 Chiroptera

   Fereuungulata   
   Ferae   

 Pholidota


 Carnivora


   Euungulata   

 Perissodactyla    


 Cetartiodactyla






"Chiroptera" from Ernst Haeckel's Kunstformen der Natur, 1904
The traditional classification of bats is:
Megabats primarily eat fruit or nectar. In New Guinea, they are likely to have evolved for some time in the absence of microbats, which has resulted in some smaller megabats of the genus Nyctimene becoming (partly) insectivorous to fill the vacant microbat ecological niche. Furthermore, some evidence indicates 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 nonflying mammals on those islands.

Fossil bats

Fossilized remains of bats are few, as they are terrestrial and light-boned. Only an estimated 12% of the bat fossil record is complete at the genus level.[30] 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.[31][32] This intermediate fossil has helped to resolve a long-standing disagreement regarding whether flight or echolocation developed first in bats. The shape of the rib cage, faceted infraspious fossa of the scapula, manus morphology, robust clavical, and keeled sternum all indicated Onychonycteris was capable of powered flight. However, the well-preserved skeleton showed that the small cochlea of the inner ear did not have the morphology necessary to echolocate. O. finneyi lacked an enlarged orbical apophysis on the malleus, and a stylohyal element with an expanded paddle-like cranial tip—both of which are characteristics linked to echolocation in other prehistoric and extant bat species.[17] Because of these absences, and the presence of characteristics necessary for flight, Onychonycteris provides strong support for the “flight first” hypothesis in the evolution of flight and echolocation in bats.

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.[17] Such physical characteristics suggest that 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.[33] The distinctive features noted on the Onychonycteris fossil also support the claim that mammalian flight most likely evolved in arboreal gliders, rather than terrestrial runners. This model of flight development, commonly known as the "trees-down" theory, implies that bats attained powered flight by taking advantage of height and gravity, rather than relying on running speeds fast enough for a ground-level take off. [34]

Habitats

Flight has enabled bats to become one of the most widely distributed groups of mammals.[35] Apart from the Arctic, the Antarctic and a few isolated oceanic islands, bats exist all over the world.[36] 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. Most temperate species additionally need a relatively warm hibernation shelter. Bat roosts can be found in hollows, crevices, foliage, and even human-made structures, and include "tents" the bats construct by biting leaves.[37]

The United States is home to an estimated 45 to 48 species of bats.[38][39] 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 bats are common throughout the northern two-thirds of the country, while the Mexican free-tailed bat is the most common species in the southwest,[40] sometimes even appearing in portions of the Southeast.

Anatomy


Skeleton of a Myotis myotis (greater mouse-eared bat)

Scapulae, spine and ribs of Myotis lucifugus (little brown bat)

Wings


A preserved fruit bat showing how the skeleton fits inside its skin

Thermographic image of a bat using trapped air as insulation

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. In 2006, Sears et al. published a study that traces the elongation of manual bat digits, a key feature required for wing development, to the upregulation of bone morphogenetic proteins (Bmps). During embryonic development, the gene controlling Bmp signaling, Bmp2, is subjected to increased expression in bat forelimbs - resulting in the extension of the offspring's manual digits. This crucial genetic alteration helps create the specialized limbs required for volant locomotion.[41]

The wings of bats are much thinner than those of birds, allowing bats to maneuver more quickly and more accurately than birds.[citation needed] They are also delicate, ripping easily;[42] however, the tissue of the bat's membrane is able to regrow, such that small tears can heal quickly.[42][43] 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 center,[44] 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.[44] 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.[44] The cells are concentrated in areas of the membrane where insects hit the wings when the bats capture them.

Other

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 their veins to prevent the blood from flowing backwards, but bats also have one-way valves in their 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.[45]

Echolocation

Spectrogram of Pipistrellus pipistrellus (common pipistrelle) bat vocalizations — one echolocation call, followed by series of multiharmonic pulses, forming a social call (here, precisely, an advertisement call, produced by territorial male during the mating season in autumn).[46]

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.[47]

To clearly distinguish returning information, bats must be able to separate their calls from the echoes that they receive. Microbats use two distinct approaches.
  1. Low duty cycle echolocation: Bats can separate their calls and returning echoes 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 the call and echo allows them to relax these muscles, so they can clearly hear the returning echo.[48] The delay of the returning echoes provides the bat with the ability to estimate range to their prey.
  2. 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 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.[49]
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.[50]

Two groups of moths exploit a bat sense to echolocate: tiger moths produce ultrasonic signals to warn the bats that they (the moths) are chemically protected or aposematic, other moth species 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 maneuvers.

Plecotus auritus, the brown long-eared bat

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.[51][52][53]

By repeated scanning, bats can mentally construct an accurate image of the environment in which they are moving and of their prey item.[54]

Other senses

Although the eyes of most microbat species are small and poorly developed, leading to poor visual acuity, no species is blind.[55] Microbats use vision to navigate, especially for long distances when beyond the range of echolocation,[56] and species that are gleaners—that is, ones that attempt to swoop down from above to ambush tasty insects like crickets on the ground or moths up a tree—often have eyesight about as good as a rat's. Some species have been shown to be able to detect ultraviolet light, and most cave dwelling species have developed the ability to utilize very dim light.
They also have high-quality senses of smell and hearing. Bats hunt at night, reducing competition with birds, minimizing contact with certain predators, and travel large distances (up to 800 km) in their search for food.[4]

Megabat species often have excellent eyesight as good as, if not better than, human vision; they need this for the warm climates they live in and the very social world they occupy, where relations and friends need to be distinguished from other bats in the colony. This eyesight is, unlike its microbat relations, adapted to both night and daylight vision and enables the bat to have some colour vision whereas the microbat sees in blurred shades of grey.

Behaviour

Most microbats are nocturnal[57] and are active at twilight. A large portion of bats migrate hundreds of kilometres to winter hibernation dens,[58] while some pass into torpor in cold weather, rousing and feeding when warm weather allows for insects to be active.[59] Others retreat to caves for winter and hibernate for six months.[59] Bats rarely fly in rain, as the rain interferes with their echolocation, and they are unable to locate their food.

The social structure of bats varies, with some leading solitary lives and others living in caves colonized by more than a million bats.[60] 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 that bats make all kinds of sounds to communicate with others. Scientists in the field have listened to bats and have been able to associate certain sounds with certain behaviours that bats make after the sounds are made.[60]

Insectivores make up 70% of bat species and locate their prey by means of echolocation. Of the remainder, most feed on fruits.[61] Only three species sustain themselves with blood.

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.[61] One species, the greater noctule bat, catches and eats small birds in the air.

Predators of bats include bat hawks, bat falcons and even spiders.[62]

Reproduction


Newborn common pipistrelle, Pipistrellus pipistrellus

Colony of mouse-eared bats, Myotis myotis

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.[63] 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 bat population growth is limited by the slow birth rate.[64]

Hunting, feeding, and drinking

A very young bat in Tamil Nadu

Newborn bats rely on the milk from their mothers.[65] 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.[66]

Hunting


This Philippines bat circles the sweet manzanitas fruits of the Aratiles tree (Muntingia).

Most bats are nocturnal creatures. Their daylight hours are spent grooming and sleeping; they hunt during the night. 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 that the bats with plugged ears were not able to fly with the same amount of skill and precision as they were able to without their ears plugged. Unfortunately for Spallanzani, the twin concepts of sound waves and acoustics would not be understood for another century and he could not explain why specifically the bats were crashing into walls and the threads that he'd strung up around the room, and because of the methodology Spallanzani used, many of his test subjects died.

It was thus well known through the nineteenth century that the chiropteran ability to navigate had something to do with hearing, but how they accomplish this was not proven conclusively until the 1930s, by Donald R. Griffin, a biology student at Harvard University. Using a locally native species, the little brown bat, he discovered that bats use echolocation to locate and catch their prey. When bats fly, they produce a constant stream of high-pitched sounds. 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.[66]

Feeding and diet

The majority of food consumed by bats includes insects, fruits and flower nectar, vertebrates and blood.[67] Almost three-fourths of the world's bats are insect eaters. Bats consume 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 that a group of a thousand bats could eat four tons of insects each year. If bats were to become extinct, it has been calculated that the insect population would reach an alarmingly high number.[68]
Vitamin C
In a test of 34 bat species from six major families of bats, including major insect- and fruit-eating bat families, all were found to have lost the ability to synthesize vitamin C, and this loss may derive from a common bat ancestor, as a single mutation.[69] However, recent results show that there are at least two species of bat, the frugivorous bat (Rousettus leschenaultii) and insectivorous bat (Hipposideros armiger), that have retained their ability to produce vitamin C.[70] In fact, the whole Chiroptera are in the process of losing the ability to synthesize Vc which most of them have already lost.[71]
Aerial insectivores
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.[66] 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".[65] 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.[67] One common insect prey is Helicoverpa zea, a moth that causes major agricultural damage.[72]
Forage gleaners
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.[65]
Fruits and flower nectar

A colony of great fruit-eating bats

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.[65] 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.[68] Over 150 types of plants depend on bats in order to reproduce.[68]

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.[65] 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.[68] The rainforest is said to be the most benefitted of all the biomes where bats live, because of the large variety of appealing plants.[73] Because of their specific eating habits, nectar-feeding bats are more prone to extinction than any other type of bat.[74] However, bats benefit from eating fruits and nectar just as much as from eating insects.[75]
Vertebrates
A small group of carnivorous bats feed on other vertebrates and are considered the top carnivores of the bat world.[65] These bats typically eat a variety of animals, but normally consume frogs, lizards, birds, and sometimes other bats.[68] 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.[65] 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.[65]
Blood
A few species of bats exclusively consume blood as their diet. This type of diet is referred to as hematophagy, and three species of bats exhibit this behavior. 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.[76] These species live only in Mexico, Central, and South America, with a presence also on the Island of Trinidad.

Defecation

Bat dung, or guano, is so rich in nutrients that it is mined from caves, bagged, and used by farmers to fertilize their crops. During the U.S. Civil War, guano was used to make gunpowder.[68]

To survive hibernation months, some species build up large reserves of body fat, both as fuel and as insulation.[66]

Drinking

In 1960, Frederic A. Webster discovered bats' method of drinking water using a high-speed camera and flashgun that could take 1,000 photos per second. Webster's camera captured a bat skimming the surface of a body of water, and lowering its jaw to get just one drop of water. It then skimmed again to get a second drop of water, and so on, until it has had its fill. A bat's precision and control during flight is very fine, and it almost never misses.[66] Other bats, such as the flying fox or fruit bat, gently skim the water's surface, then land nearby to lick water from chest fur.[77]

Conservation efforts

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.

Artificial roosts


Very large bat house, Tallahassee, Florida, United States

Bat roost with Charles Augustus Rosenheimer Campbell in San Antonio, Texas in 1915

Many people put up bat houses to attract bats just as some put up birdhouses to attract birds. Reasons for this vary, but most revolve 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.[78] Some conservation societies give away free bat houses to enthusiasts worldwide.[citation needed]

Constructed in March 1991, the University of Florida bat house is the largest occupied artificial roost in the world. The bat house has approximately 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 odor 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.[79]

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.[80][81]

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.[citation needed]

Nectar-rich plants attracting moths

Besides mosquitoes, some species of bats also consume moths. Moths benefit from the availability of nectar-rich plants as Matthiola bicornis, Nicotiana, ...)[82] As such, by planting these plants, bats are indirectly benefitted as well.

Threats


A little brown bat with white nose syndrome

While conservation efforts are in place to protect bats, many threats still remain. Bats are known to carry diseases communicable to humans, such as rabies.

White nose syndrome

White nose syndrome is a condition associated with the deaths of millions of bats in the Eastern United States and Canada.[83] The disease is named after a white fungus, Pseudogymnoascus destructans, found growing on the muzzles, ears, and wings of afflicted bats. This fungus, which is mostly spread from bat to bat, is the sole cause of the disease.[84] 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 caves.[85] 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.[86] As of June 2014 this fungus is doing a large amount of damage to the populations of bats that use the caves of the Appalachian Mountains in the Southeastern United States, including the Mammoth Cave system in Kentucky, which was one of the largest hibernacula in the East as recently as 2010, able to hold over a million bats. In Canada, the provinces of Quebec, Ontario, and the Maritimes [87] have witnessed identical die offs, with the Canadian government making preparations to protect the remaining bat populations in Manitoba, Alberta, Saskatchewan, and British Columbia, since scientific evidence suggests that longer winters where the fungus has a longer period of time to infect bats is a threat to Canadian bats.[88]
Scientists in both countries are alarmed that the lack of bug-eating bats in summer could cause severe problems in the ecosystem of the Eastern forests and on farmland and beyond: nearly all of the bats Continental US and Canada are insectivores, and save the government billions in pesticides because they are natural predators of bugs that eat crops like cabbages, potatoes, pears, cherries, peaches, apples, wheat, and corn, consuming tons of them from late May-early October which coincides with the height of planting and harvest. They are also facing the possibility that once common species with robust numbers could go extinct given the rapid progress the disease has made in less than a decade. There is evidence that at least one species, the little brown bat, has started to change its roosting behavior, which scientists hope may yet save the species from extinction[89] Unfortunately, this does not negate the fact that their numbers have undergone a very steep crash. They were up until 2008 the most common bat in the East, and were often seen catching moths attracted to street lamps in New York City, Montreal, and the average small town; they were once so common in the average town that citizens often discovered them roosting in maternity colonies in late spring in their attics. As of 2014, scientists are reckoning that unless something changes soon, the subspecies myotis lucifugus lucifugus may face total population collapse since the population of survivors is dangerously low in an area nearly the size of France.[90] In July 2014 the US state of Maine recorded a population of this subspecies that is now so low that it and the northern long eared bat are candidates for the state endangered species list, after both being plentiful only seven years earlier.[91]

The most recent scholarship suggests that the pseudogymnoascus fungus is native to Europe where it is part of the naturally occurring biota found on the walls of caves, and is harmless to the myotis, bentwing, pipistrelle, and horseshoe bat species that live there. However, as a novel pathogen, it has proven to be lethal to North American bat species that utilise caves or abandoned mines. Unlike European species, most cave dwelling North American bat species form very large winter colonies that can number from a few hundred to many thousands, with bats forming tight clusters on the walls and ceilings of caves and mines. Most North American species shall even migrate many hundreds of miles in September from other states to a very specific type of cave or mine that has a constant temperature of 7.2 °C to 10 °C. They cluster together to conserve body heat and counteract the (compared to most of Europe) colder winter temperatures that may blow in from outer portions of the hibernaculum. Without the natural immunities of their European cousins, these North American bats go into hibernation in autumn a few weeks before Halloween, often forming huge swarms of males and females outside the cave or mine entrance that join up to mate before going off to sleep until spring comes in late March. Normally, they will have been eating moths, beetles, mosquitoes, potato bugs, and flies all summer long and have gained weight to prepare for winter. However, once they enter torpor, their immune system response is suppressed to conserve energy and hibernate through winter. Eventually the bat becomes infected by the fungus, the fungus desiccates the bat's wings, upsetting hydrostatic balance, and the bat, chronically thirsty, is forced to wake up more often than it must, using up its fat reserves, and eventually dying from dehydration and starvation. By then it will have infected several more of its neighbours in the cluster, over time causing hundreds or even thousands to die in a single winter. This number includes what would have been the following season’s offspring, dead with the pregnant mothers, and has a knock on effect on the populations in other states and provinces that never see the return of migratory bats in spring. Aeolus Cave in New England had a headcount numbering 300,000 in 2008. When scientists went to make their count in the spring of 2014, more than 270,000 had already perished and the floors of the caves were covered up to the ankles of researchers with the bones of thousands of bats.[92]

Species thus far that have been badly affected include the little brown bat, the endangered gray myotis, the endangered Indiana bat, the northern long-eared myotis, the eastern small-footed myotis, the tri-coloured bat, and two subspecies of Townsend's big-eared bat. More than half of all bat species that live in North America use caves at some point in their life cycle; in the East, though infected specimens have been caught, only tree dwelling bats of the Lasiurus family and Eptesicus fuscus, a relative of the serotine bat, seem to have been minimally affected: these species are far less dependent on caves for their winter survival and the last mentioned species does not cluster tightly if it is underground at all and will also accept manmade structures to hibernate in. As of 2014, the geographical spread of white nose syndrome in North American bats has worsened in the sense that infection has crossed the Mississippi River:[93] Species native to northern Mexico and the West have not yet been affected, but it remains unknown how or if white nose syndrome shall affect bat species here.[94] All North American bat species have a very slow reproductive rate: with the exception of a handful of species like the little brown bat, which occasionally gives birth to twins, most females give birth to only one pup a year. Though measures are being taken to slow the spread of the disease and a cure is being sought, the recovery of bats In North America may take decades if not centuries due to this fungus and the prognosis for the future of bats is grim.[citation needed]

Barotrauma and wind turbines

Evidence suggests barotrauma is causing bat fatalities around wind farms.[95] 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.[96] Bats suffer a higher death rate than birds in the neighborhood of wind turbines.[97][98][99] 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.[100] In addition, it has been suggested that bats are attracted to these structures, perhaps seeking roosts, and thereby increasing the death rate.[96] Acoustic deterrents may prove beneficial in mitigating bat mortality at wind energy facilities.[101]

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,[102] including rabies,[103] severe acute respiratory syndrome (SARS),[104] Henipavirus (i.e. Nipah virus and Hendra virus)[105] and possibly ebola virus.[106][107] 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.[citation needed]

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.[108] 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.[109] 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 bat rabies virus can infect victims purely through airborne transmission ("cryptic rabies"), without direct physical contact of the victim with the bat itself. This phenomenon has very rarely been reported, and has occurred among victims breathing virus-infected air in environments such as caves, after long exposures.[110][111]

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 that the bat can be analysed. This also applies if the bat is found dead. If it is certain that 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 in some regions, bats should be excluded from inhabited parts of houses. The Centers for Disease Control and Prevention (CDC) provide fully detailed information on all aspects of bat management in North America, including how to capture a bat, what to do in case of exposure, and how to bat-proof a house humanely.[112] In certain countries, such as the United Kingdom, it is illegal to handle bats without a license and advice should be sought from an expert organisation, such as the Bat Conservation Trust, if a trapped or injured bat is found.

Where rabies is not endemic, as throughout most of Western Europe, small bats can be considered harmless. Larger bats can give a nasty bite.

Bats in human culture

Mythology


Common fruit bat (Rousettus aegyptiacus) flying

In European cultures, bats have long been associated with witchcraft, black magic and darkness. The Weird Sisters incorporate the fur of a bat in their brew in Shakespeare's Macbeth, written around 1603-1605.[113] Because bats are mammals, yet can fly, this gives them status as liminal beings in many cultural traditions.[114] 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.

Among some Native Americans, such as the Creek, Cherokee and Apache, the bat is a trickster spirit. In Tanzania, a winged bat cryptid known as Popobawa, is believed to be a shapeshifting evil spirit that assaults and sodomises its victims.[115]

Not all legends surrounding bats are negative, Chinese lore claims that the bat is a symbol of longevity and happiness, and is similarly lucky in Poland, geographical Macedonia and among the Kwakiutl and Arabs.

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.

Aztec

In Mesoamerican mythology during the Classic-Contemporary period, bats symbolized the land of the dead, which was considered to be the underworld.[116] 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.[117] Bat images were engraved onto funerary urns, and were emphasized with large claws and round ears by Zapotecs. They were commonly associated with death.[118] 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. Pre-Columbian cultures associated animals with gods, and often displayed them in art. The Moche people depicted bats in their ceramics.[119]

A life-size, ceramic bat-man was discovered and dug up from the Templo Mayor.[120] The Templo Mayor is located in the center 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".[121] 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.[122]

Oaxaca


Zapotec bat god

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 color 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.[122]

East Nigeria

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 the bat prepared his soup, the bush-rat came, greeting him and asking if he could be shown what was agreed yesterday. Earlier, the bat had 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 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 he flew out of hiding every night to hunt for food to avoid being arrested. This, according to Eastern Nigeria mythology, is why bats only fly at night.[123]

Tongan

The bat is sacred in Tonga and is often considered the physical manifestation of a separable soul.[124]

Heraldry

Burgee of the Royal Valencia Yacht Club

The bat is sometimes used as a heraldic symbol in Spain. 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. 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.

Non heraldic organizations also use bats in their symbols. 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 center.[citation needed]

State symbols

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.[125]