As bats fly, they issue a continuous stream of high-pitched sounds at the rate of about 30 per second. The frequency of these sounds starts at approximately 30,000 cycles, the extreme upper limit of human hearing, and ranges upward to 60,000 cycles. The squeaking of a roosting bat is at a much lower frequency and easily discernible to the human ear. If a bat picks up an echo from one of its sounds, it instantly speeds up the rate of discharge until the signals are coming at 50-60 per second. The pattern formed by the echoes tells the bat of obstacles, their size, shape, and location.
Bats can thus easily locate their prey, night-flying insects, as well.
This is referred to as echolocation. Another membrane extends from the inside of the hind legs to the tail, leaving the hind feet free for gripping as the bat hangs upside down in its roost. Ears Bats have greatly enlarged ears, necessary for night flying, which they keep meticulously clean with their sharp thumbs. The thumbs of the forefoot are small, equipped with sharp claws and not connected to the membrane. Behavior Bats are very shy creatures and like most wild animals, avoid contact with humans while going about their business of eating, reproducing and avoiding predators.