Bats are mammals in the order Chiroptera. Their most distinguishing feature is that their forelimbs are developed as wings, making them the only mammal in the world naturally capable of flight; other mammals, such as flying squirrels and gliding phalangers, can glide for limited distances but are not capable of true sustainable flight. The word Chiroptera can be translated from the Greek words for “hand wing,” as the structure of the open wing is very similar to an outspread human hand, with a membrane (patagium) between the fingers that also stretches between hand and body.

There are estimated to be about 1,100 species of bats worldwide, accounting for about 20% of all mammal species.

About 70 percent of bats are insectivorous. Most of the remainder feed on fruits and their juices; three bat species sustain themselves with blood and some prey on vertebrates. These bats include the leaf-nosed bats (Phyllostomidae) of central America and South America, and the related bulldog bats (Noctilionidae) that feed on fish. There are at least two known species of bat that feed on other bats: the Spectral Bat or American False Vampire bat and the Ghost Bat of Australia.

Some of the smaller bat species are important pollinators of some tropical flowers. Indeed, many tropical plants are now found to be totally dependent on them, not just for pollination, but for spreading their seeds by eating the resulting fruits. This role explains environmental concerns when a bat is introduced in a new setting. Tenerife provides a recent example with the introduction of the Egyptian fruit bat.