AFCT Practice Test 4

Hunting by Sound

Many bats hunt in complete darkness by using echolocation. A bat produces short, high-pitched calls, most of them far above the range of human hearing, and listens for the echoes that bounce back from objects around it. The time it takes an echo to return tells the bat how far away an object is, and subtle changes in the echo reveal the object's size, shape and even texture. As a bat closes in on an insect, it calls faster and faster, sometimes producing more than a hundred calls per second in a final rapid burst. Some moths have evolved ears that detect these calls; when such a moth hears a bat approaching, it may fold its wings and drop abruptly toward the ground.