"Blind as a bat" is an common expression. Bats can actually see. But they don't depend on eyesight to guide them when they fly around at night hours. They rely on the echoes of their own voices.
A bat broadcasts its voice in short, quick squeaks. The squeaks bounce back from any object nearby — even from a telephone wire only a few inches away. The bat's keen ears pick up the echo. Instantly it knows just where the wire is. So it can swerve to one side.
Bats have to hunt for their food in the dark. Some of them eat the nectar of flowers. Others eat moths, mosquitoes or other insects that fly at night. A bat uses echoes to locate the insects.
A bat's voice is too high for our ears to hear, but scientists have used sensitive machines to pick up the sound. They have also done experiments to prove that echolocation works. First they blindfolded a bat. It flew without bumping into anything. Then they taped its ears shut. It flew into obstacles it had missed before.
