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Bats are flying mammals in the order Chiroptera . The forelimbs of bats are webbed and developed as 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, glide rather than fly, and 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. Chiroptera comes from two Greek words, cheir (χείρ) "hand" and pteron (πτερόν) "wing."

 

There are about 1,100 bat species worldwide, which represent about twenty percent of all classified mammal species.About seventy percent of bats are insectivores. Most of the rest are frugivores, or fruit eaters. A few species feed from animals other than insects. Bats are present throughout most of the world and perform vital ecological roles such as pollinating flowers and dispersing fruit seeds. Many tropical plant species depend entirely on bats for the distribution of their seeds.

 

Bats range in size from Kitti's Hog-nosed Bat measuring 29–33 mm (1.14–1.30 in) in length and 2 g (0.07 oz) in mass, to the Giant Golden-crowned Flying-fox, which has a wing span of 1.5 m (4 ft 11 in) and weighs approximately 1.2 kg (3 lb).

Bats are mammals. Sometimes they are mistakenly called "flying rodents" or "flying rats", and they can also be mistaken for insects and birds. There are two suborders of bats:

 

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 a well-developed visual cortex 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 that was 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.

 

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

 

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, 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 fifteen-base pair deletion in BRCA1 and a seven-base pair deletion in PLCB4 present in all Yangochiroptera and absent in all Yinpterochiroptera.[6] 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. 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

Analyses of the sequence of the "vocalization" gene, FoxP2 was inconclusive of whether laryngeal echolocation was secondarily lost in the pteropodids or independently gained in the echolocating lineages[10]. However, analyses of the "hearing" gene, Prestin seemed to favor 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.

 

In the 1980s, a hypothesis based on morphological evidence was offered that stated that the Megachiroptera evolved flight separately from the Microchiroptera. The so-called flying primates theory proposed that when adaptations to flight are removed, the Megachiroptera are allied to primates by anatomical features that are 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 support the monophyly of bats, debate continues as to the meaning of available genetic and morphological evidence.

 

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. The oldest known definitely identified bat fossils, such as Icaronycteris, Archaeonycteris, Palaeochiropteryx and Hassianycteris, are from the early Eocene period, 52.5 million years ago. These fossil bats were already very similar to modern microbats. 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

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 Eocene bat, Onychonycteris finneyi, was found in the fifty-two-million-year-old Green River Formation in South Dakota, United States, in 2004 and was added as a new genus and placed in a new family when published in Nature in 2008. It had characteristics indicating that it could fly, yet the well-preserved skeleton showed that the cochlea of the inner ear lacked development needed to support the greater hearing abilities of modern bats. This provided evidence that flight in bats developed well before echolocation. The team that found the remains of this species, named Onychonycteris finneyi, recognized that it lacked ear and throat features present not only in echolocating bats today, but also in other known prehistoric species. Fossil remains of another Eocene bat, Icaronycteris, were found in 1960.

 

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 broad, short wings suggesting that it could not fly as fast or as far as later bat species. Instead of flapping its wings continuously while flying, Onychonycteris likely alternated between flaps and glides while in the air. 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

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.

 

1.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 that 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 provide 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 echos yield 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 that are supported by molecular evidence, suggest 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 Horse-Shoe bats; or echolocation was evolved independent in both the Yinpterochiroptera and Yangochirpotera lineages.

 

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. 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 manoeuvres.

 

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 youngsters until they are nearly adult size; this is 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. 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 6 to 8 weeks, 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

Most bats are nocturnal creatures. Their daylight hours are spent grooming, sleeping, and resting; it is during the nighttime hours that they hunt. 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 submerged 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 that the bats were not using their eyes to fly through complete darkness, but something else.

 

Spallanzani decided that 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 that 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 wasn’t discovered until the 1930s, by one Donald R. Griffin. Griffin, who was a biology student at Harvard College at the time, discovered that bats use echolocation to locate and catch their prey. When bats fly, they produce a constant stream of high-pitched sounds that 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.

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. Each of these bats is 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 one thousand bats could eat four tons of insects each year. If bats were to become extinct, the insect population would reach an alarmingly high number.

 

The types of insects consumed by bats can be divided into two categories: aerial insects, and ground-dwelling insects.

 

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

Nycteridae is the family of slit-faced or hollow-faced bats. They are grouped in a single genus, Nycteris. The bats are found in East Malaysia, Indonesia and many parts of Africa.

 

They are small bats, from 4 to 8 cm in body length, and with grey, brown, or reddish fur. A long slit runs down the centre of their faces from between the eyes to the nostrils, and probably assists in echolocation. They have large ears, and a complex nose-leaf. Their tail ends in a T-shape, formed from cartilage, a feature that is unique among mammals. Their dental formula is:

 

Slit-faced bats roost in caves, trees, and buildings, typically in fairly small colonies. Some even roost in animal burrows, such as those of hedgehogs or porcupines. They eat insects, and some terrestrial invertebrates, such as spiders and small scorpions. At least one species, the Large Slit-Faced Bat, even catches vertebrate prey, such as frogs and small birds.

 

The echolocation calls of slit-faced bats are relatively quiet and short in duration, and they seem to target their prey by hearing the sounds it produces, rather than by sonar. They give birth once or twice each year.

The Egyptian Slit-Faced Bat (Nycteris thebaica) is a species of slit-faced bat broadly distributed throughout Africa and the Middle East. It can live in widely diverse habitats, including forests, caves, deserts, savannas, shrublands, and grasslands.

Nycteridae is the family of slit-faced or hollow-faced bats. They are grouped in a single genus, Nycteris. The bats are found in East Malaysia, Indonesia and many parts of Africa.

 

They are small bats, from 4 to 8 cm in bodgy length, and with grey, brown, or reddish fur. A long slit runs down the centre of their faces from between the eyes to the nostrils, and probably assists in echolocation. They have large ears, and a complex nose-leaf. Their tail ends in a T-shape, formed from cartilage, a feature that is unique among mammals. Their dental formula is:

 

Slit-faced bats roost in caves, trees, and buildings, typically in fairly small colonies. Some even roost in animal burrows, such as those of hedgehogs or porcupines. They eat insects, and some terrestrial invertebrates, such as spiders and small scorpions. At least one species, the Large Slit-Faced Bat, even catches vertebrate prey, such as frogs and small birds.

 

The echolocation calls of slit-faced bats are relatively quiet and short in duration, and they seem to target their prey by hearing the sounds it produces, rather than by sonar. They give birth once or twice each year.