Bats are mammals of the order Chiroptera.[a] With their forelimbs
adapted as wings, they are the only mammals capable of true and
sustained flight. Bats are more agile in flight than most birds, flying
with their very long spread-out digits covered with a thin membrane or
patagium. The smallest bat, and arguably the smallest extant mammal, is
Kitti's hog-nosed bat, which is 29–34 millimetres. The largest bats are
the flying foxes, with the giant golden-crowned flying fox.
Bats are present throughout the world, with the exception of extremely
cold regions. They are important in their ecosystems for pollinating
flowers and dispersing seeds; many tropical plants depend entirely on
bats for these services.
Bats provide humans with some direct benefits, at the cost of some
disadvantages. Bat dung has been mined as guano from caves and used as
fertiliser. Bats consume insect pests, reducing the need for pesticides
and other insect management measures. They are sometimes numerous enough
and close enough to human settlements to serve as tourist attractions,
and they are used as food across Asia and the Pacific Rim. However,
fruit bats are frequently considered pests by fruit growers. Due to
their physiology, bats are one type of animal that acts as a natural
reservoir of many pathogens, such as rabies; and since they are highly
mobile, social, and long-lived, they can readily spread disease among
themselves. If humans interact with bats, these traits become
potentially dangerous to humans. Some bats are also predators of
mosquitoes, suppressing the transmission of mosquito-borne diseases.