Thursday, February 7, 2008

Bat

The bat is winged mammal, with the ability to fly. Its ability to maintain sustained flight, unique among mammals, result from the modification of hand like forelimbs into wings. Bats belong to the order Chiroptera. There are two suborders: the Megachiroptera (megabats) and the Microchiroptera (microbats). Bats are nocturnal or active at twilight (crepuscular). They are mainly tropical in distribution.

Most megabats have a claw on the second finger and an unspecialized shoulder girdle. Their average weight is more than 100 g (3.5 oz). The largest megabats, Pteropus vampyrus, weighs up to 899 g (31.7 oz) and have wingspan of 170 cm (67 in). In contrast, microbats have no claw on the second finger. Their average weight is less than 30 g (1.058 oz) as adults. The smallest microbat, weight from 1.8 to 2.0 g (0.063 to 0.07 oz) and has a wingspat of about 16 cm (16.3).

Nearly two-thirds of the 850 species of bats feed mainly on insects. All insectivorous bats are microbats. Fruit eater and nectar and pollen feeders may be either megabats of the family Pteropodidae of the Old World tropics. In other families of microbats, such as the Vespertilionidae and the Noctilionidae, bats are fish eaters. In India, Southeast Asia, Australia, and South America, several species in two families of microbats, the Megadermatidae and the Phyllostomidae, are carnivorous, eating birds, small mammals and reptiles.

The three species of vampires (blood-feeding microbats) all are found in the New World tropics. Vampires are usually treated as part of the family Phyllostomatidae. Vampires feed on blood obtained from mammals or birds. They use their sharp, highly modified teeth to make a shallow wound, and they secrete an anticoagulant in their saliva to inhibit clotting of the blood. The vampire's bite is painful but not usually dangerous, though the saliva may transmit certain dieses.

Bats have low rates of reproduction. Most species produce one or two young in a litter; bats of temperate areas have one litter a year, and those in tropical regions may have two. Some tropical bats are polyestrous and annually produce more than two litter.

All the Microchiroptera that have been studied and several species of dog-faced bats use Echolocation to orient themselves. Bats are not blind, however, and their eyes and sense of smell are well developed. Vocalizations, visual signals, and smell play important roles in the social lives of bats, which are among gregarious of the Mammalia.

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