Bats (order Chiroptera /kaɪˈrɒptərə/) are winged mammals; the only mammals capable of true and sustained flight. Bats are more agile in flight than most birds, flying with their long spread-out digits covered with a thin membrane or patagium. The smallest bat, and one of the smallest extant mammals, is Kitti's hog-nosed bat, which is 29–33 mm (1.1–1.3 in) in length, 150 mm (5.9 in) across the forearm and 2 g (0.071 oz) in mass. The largest bats are the flying foxes, with the giant golden-crowned flying fox (Acerodon jubatus) reaching a weight of 1.5 kg (3.3 lb) and having a wingspan of 1.6 m (5 ft 3 in).
The second largest order of mammals after rodents, bats comprise about 20% of all classified mammal species worldwide, with at least 1,500 known species. These were traditionally divided into two suborders: the largely fruit-eating megabats and the echolocating microbats. But more recent evidence has supported dividing the order into Yinpterochiroptera and Yangochiroptera, with megabats as members of the former along with several species of microbats. Many bats are insectivores, and most of the rest are frugivores (fruit-eaters) or nectarivores (nectar-eaters). A few species feed on animals other than insects; for example, the vampire bats are haematophagous (feeding on blood). Most bats are nocturnal, and many roost in caves or other refuges; it is uncertain whether bats have these behaviours to escape predators. Bats are distributed globally in all except the coldest regions. They are important in their ecosystems for pollinating flowers and dispersing seeds as well as controlling insect populations.
