FREE-TAILED BAT

also called Mastiff Bat, any of about 90 species of bats of the family Molossidae, suborder Microchiroptera. Free-tailed bats are found worldwide in warm regions. Their common name is descriptive of the way in which part of the tail extends beyond the membrane attached between the hind legs. Free-tailed bats are also known as mastiff, or bulldog, bats because of their supposed facial resemblance to these dogs. Swift fliers with stout bodies and long, slender wings, free-tailed bats are small-eyed, often heavy-snouted bats about 413 cm (1.65 inches) long excluding the 1.58-centimetre (0.63-inch) tail. Their ears are large and are joined across the forehead in some species. Except for the naked free-tailed bat (Cheiromeles), which is almost hairless, they have short, usually dark fur. Free-tailed bats eat insects and roost in tree hollows, caves, and buildings. Most species live in groups, and some, such as the Mexican free-tailed bat (Tadarida brasiliensis mexicana), form colonies of several million individuals. In the past, guano from this species' colonies was mined for fertilizer and for sodium nitrate, which was used to make gunpowder. Free-tailed bats do not hibernate, but some species become inactive in winter; other species migrate seasonally.