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Bat

From Academic Kids

Bats
Leaf-nosed bat
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Mammalia
Order:Chiroptera
Families

Pteropodidae
Emballonuridae
Rhinopomatidae
Craseonycteridae
Rhinolophidae
Nycteridae
Megadermatidae
Vespertilionidae
Molossidae
Antrozoidae
Natalidae
Myzopodidae
Thyropteridae
Furipteridae
Noctilionidae
Mystacinidae
Mormoopidae
Phyllostomidae

Bats are flying mammals in the order Chiroptera with forelimbs developed as wings. Other mammals, such as flying squirrels or gliding phalangers, can glide limited distances, but only bats are capable of true flight. The name Chiroptera can be translated as Hand Wing, as the structure of the open wing is very similar to an outspread human hand, covered in a membrane.

Though the vast majority of bats are insectivorous, a significant number from both suborders, Megachiroptera and Microchiroptera (see below), have developed the ability to feed on fruits and their juices. Some of the smaller species are important pollinators of some tropical flowers. Indeed, many tropical plants are now found to be totally dependent on them, not just as pollinators, but eating the resulting fruits and so spreading their seeds. This role explains environmental concerns when an exotic bat is introduced in a new setting. Tenerife provides a recent and particularly interesting example here, given the island's unique fauna and flora (much of it, vestiges of the ancient continent of Gondwanaland). In this case, the exotic bat threatening native species is the Egyptian Bat (Roussettus aegyptiacus) 1 (http://www.atan.org/en/animales/loroparque/murcielago.htm). In addition, some bats prey on vertebrates. These bats include the Leaf-nosed bats (Phyllostomidae) of central and South America, and the allied family Noctilionidae (Bulldog bats) that feed on fish.

Contents

Classification

Though sometimes called "flying rodents" or "flying rats," these terms are erroneous, as bats are neither rodents nor rats.

There are two suborders of bats:

  1. Megachiroptera (megabats or fruit bats)
  2. Microchiroptera (microbats, echolocating bats or insectivorous bats)

Megabats eat fruit, while microbats eat mainly insects, and often rely on echolocation for navigation and finding prey. A handful of species, the vampire bats, feed on blood.

There is controversial evidence that Megachiroptera evolved flight separately from the Microchiroptera, a group of mammals which would then be of uncertain affinities. Megachiroptera are allied to the Primates by anatomical features that are not shared with Microchiroptera, so that when adaptations to flight are discounted in a cladistic analysis the Megachiroptera are found to be allied to Primates. Genetic evidence has pointed to the common ancestry of Megachiroptera and at least some Microchiroptera; however the validity of these studies is debatable, and most studies of Eutherian relationships have attempted to avoid this issue by assuming monophyly of Chiroptera.

Little is known about the evolution of bats, since their small, delicate skeletons do not fossilize well. However a late Cretaceous tooth from South America resembles that of an early Microchiropteran bat. The oldest known definite bat fossils, such as Icaronycteris, Archaeonycteris, Palaeochiropteryx and Hassianycteris, are from the early Eocene (about 50 million years ago), but they were already very similar to modern microbats. Archaeopteropus, formerly classified as the earliest known Megachiropteran, is now classified as a Microchiropteran.

Bats are usually grouped with the tree shrews (Scandentia), colugos (Dermoptera), and the primates in superorder Archonta because of the similarities between Megachiroptera and these mammals.

Anatomy

Missing image
Bat_box_in_the_woods.jpg
Bat boxes, such as this one, can encourage bats to nest in an area.

The metacarpal bone and the second and fifth toe of the forelimbs are elongated, and between these toes is a membrane, called "chiropatagium". The membrane extends from the toes to the body side and from there to the base of the hindlimbs. The entire wing of a bat is called patagium. Many species also have a membrane between the hindlimbs enclosing the tails. This membrane is the uropatagium.

The patagium is full of fine blood vessels, muscle fibres and nerves. When it's cold, the bats wrap themselves up in their wings like in a coat. In warm weather they stir their wings in order to cool their bodies.

The thumb and sometimes the second toe of the forelimbs have claws, as do all five toes of the hindlimbs. The rear claws allow bats to hang on branches or ledges. Bats are also able to move on the ground, but they are rather clumsy.

Missing image
California_leaf-nosed_bat.jpg
Face of one bat

All bats are active at night or at twilight, so the eyes of most species are poorly developed. Their senses of smell and hearing, however, are excellent. By emitting high-pitched sounds and listening to the echoes, the microbats locate prey and other nearby objects. This is the process of echolocation, a skill they share with dolphins and whales.

The teeth resemble those of the insectivores. They are very sharp in order to bite through the chitin armour of insects or the skin of fruits.

Reproduction

A newborn bat can cling to the fur of the mother and be transported, although they soon grow too large for this. It would be difficult for an adult bat to carry more than one young, but normally only one young is born. Bats will often form nursery roosts, with many females giving birth in the same area, be it a cave, a tree hole, or a cavity in a building. Two mammary glands are situated between the chest and the shoulders. Only the mother cares for the young, and there is no continuous partnership.

The ability to fly is congenital, but after birth the wings are too small to fly. Young microbats become independent at the age of 6 to 8 weeks, megabats not until they are four months old. At the age of two years bats are sexually mature.

Enemies

Small bats are sometimes preyed upon by owls and falcons. Generally there are few animals able to hunt a bat. In Asia there is a bird, the bat hawk, which specializes in hunting bats. The domestic cat is a regular predator in urban areas; they may catch bats as they enter or leave a roost, or on the ground. Bats will land on the ground for feeding, in bad weather, or due to accidents while learning to fly.

The worst enemies are parasites. The membranes with all their blood vessels are ideal food sources for fleas, ticks and mites. Some groups of insects suck exclusively bat blood, e.g. the bat fly. In their caves the bats are hanging close together, so it is easy for the parasites to infest new hosts.

The most destructive enemy of bats is probably humans, who fear the harmless animal either because of superstition or fear of rabies. Destruction of bat habitat and elimination of their food scource (primarily insects) negatively affects the species.

Vector for rabies

A big brown bat (Eptesicus fuscus) approaches a wax moth (Galleria mellonella), which serves as the control species for the studies of the tiger moths. The moth is only "semi-tethered," allowing it the mobility to fly evasively.
Enlarge
A big brown bat (Eptesicus fuscus) approaches a wax moth (Galleria mellonella), which serves as the control species for the studies of the tiger moths. The moth is only "semi-tethered," allowing it the mobility to fly evasively.

The following advice is only relevant to areas with endemic rabies.

Of the very few cases of rabies reported in the United States every year, most are caused by bat bites. Although most bats do not have rabies, those that do may be clumsy, disoriented, and unable to fly, which makes it more likely that they will come into contact with humans. Although one should not have an unreasonable fear of bats, 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, the person or pet should receive immediate medical attention for rabies. Bats have very small teeth and can bite a sleeping person without necessarily being felt.

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 analyzed. 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 is to close all the doors and windows to the room except one to the outside. The bat should soon leave.

Due to the risk of rabies and also due to health problems related to their guano, bats should be excluded from inhabited parts of houses. For full 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, see the Centers for Disease Control's website on bats and rabies (http://www.cdc.gov/ncidod/dvrd/rabies/Bats_&_Rabies/bats&.htm). It should be noted that in certain countries (including the UK) 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 as harmless. Larger bats can give a nasty bite. Treat them with the respect due to any wild animal.

References

  • Greenhall, Arthur H. 1961. Bats in Agriculture. A Ministry of Agriculture Publication. Trinidad and Tobago.


Cultural aspects

The bat is sacred in Tonga and West Africa 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 a symbol of ghosts, death and disease. Among some Native Americans, such as the Creek, Cherokee and Apache, the bat is a trickster spirit. Chinese lore claims the bat is a symbol of longevity and happiness, and is similarly lucky in Poland and geographical Macedonia and among the Kwakiutl and Arabs.

In Western Culture, the bat is often a symbol of the night and its forboding nature. The bat is a primary animal associated with fictional characters of the night such as both villains like Dracula and heroes like Batman. The association of the fear of the night with the animal was treated as a literary challenge by Kenneth Oppell, who created a best selling series of novels, beginning with Silverwing, which feature bats as the central heroic figures much in a similar manner as the classic novel Watership Down did for rabbits.

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.

Austin, Texas is the summer home to North America's largest urban bat colony, an estimated 1,500,000 Mexican free-tailed bats, who eat an estimated 10,000 to 30,000 pounds of insects each night and attract 100,000 tourists each year.

See also


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