Any mammal of the order Chiroptera, related to the Insectivora (hedgehogs and shrews), but differing from them in being able to fly. Bats are the only truly flying mammals. Their forelimbs are developed as wings capable of rapid and sustained flight. There are two main groups of bats: megabats, which eat fruit, and microbats, which mainly eat insects. Although by no means blind, many microbats rely largely on echolocation for navigation and finding prey, sending out pulses of high-pitched sound and listening for the echo. Bats are nocturnal, and those native to temperate countries hibernate in winter. There are about 977 species forming the order Chiroptera, making this the second-largest mammalian order; bats make up nearly one-quarter of the world’s mammals. Although bats are widely distributed, populations have declined alarmingly and many species are now endangered.
The Megachiroptera live in the tropical regions of the Old World, Australia, and the Pacific and feed on fruit, nectar, and pollen. The hind feet have five toes with sharp hooked claws which suspend the animal head downward when resting. There are 162 species of Megachiroptera. Relatively large, up to 900 g/2 lb with a wingspan as great as 1.5 m/5 ft, they have large eyes and a long face earning them the name “flying fox”. Most orient by sight.
Many rainforest trees depend on bats for pollination and seed dispersal, and some 300 bat-dependent plant species yield more than 450 economically valuable products. Some bats are keystone species on whose survival whole ecosystems may depend.
Most bats are Microchiroptera, mainly small and insect-eating. Some eat fish as well as insects; others consume small rodents, frogs, lizards, or birds; a few feed on the blood of mammals (vampire bats). There are about 750 species. They roost in caves, crevices, and hollow trees. A single bat may eat 3,000 insects in one night. The bumblebee bat, inhabiting SE Asian rainforests, is the smallest mammal in the world.
Many microbats have poor sight and orient and hunt their prey principally by echolocation. They have relatively large ears and many have nose-leaves, fleshy appendages around the nose and mouth, that probably help in sending or receiving the signals, which are squeaks pitched so high as to be inaudible to the human ear.
The difference in the two bat groups is so marked that many biologists believe that they must have had different ancestors: microbats descending from insectivores and megabats descending from primates. Analysis of the proteins in blood serum from megabats and primates by German biologists 1994 showed enough similarities to suggest a close taxonomic relationship between the two groups.
A bat's wings consist of a thin hairless skin expansion, stretched between the four fingers of the hand, from the last finger down to the hindlimb, and from the hindlimb to the tail. The thumb is free and has a sharp claw to help in climbing. The shoulder girdle and breastbone are large, the latter being keeled, and the pelvic girdle is small. The bones of the limbs are hollow, other bones are slight, and the ribs are flattened.
An adult female bat usually rears only one pup a year, which she carries with her during flight. In species that hibernate, mating may take place before hibernation, the female storing the sperm in the genital tract throughout the winter and using it to fertilize her eggs on awakening in spring.
Nocturnal mouselike mammal with forelimbs modified to form membranous wings and anatomical adaptations for echolocation by which it navigates; SYN. chiropteran.