Chiroptera an order of mammals (class Mammalia) which includes the 178 genera of bats. Unlike other mammals, they can fly, the front limbs being modified to support a membranous wing. Most bats are nocturnal in habits and most are found in tropical regions. They are able to navigate in complete darkness by means of a kind of sonar, which uses echoes of the bats own supersonic squeaks to locate obstacles and prey. There are about 800 living species. Most are small, although they range in wingspan from 25 centimeters to 147 centimeters (10–58 inches).