The bat is the only mammal capable of sustained powered flight. Its forelimbs are modified into wings, with elongated finger bones supporting a membrane of skin.
Flying squirrels, sugar gliders and colugos can glide, but they cannot generate continuous lift through flapping flight. This distinction makes bats unique among mammals and separates them from other gliding zoo animals.
Bats evolved from small terrestrial mammals, although the exact details of their early evolution remain an area of scientific study. Modern bats are divided into two major groups: the echolocating microbats and the generally larger megabats, though that traditional division does not perfectly reflect evolutionary relationships.
There are more than 1,400 recognised bat species. They occupy habitats worldwide except Antarctica and perform important ecological roles, including insect control, pollination and seed dispersal.