How Does a Bat See in the Dark?

Step 1 of 5

Sound bounces, and bouncing takes time.

A bat calls, then waits. A near wall sends the echo back quickly; a far one takes longer. The delay tells it distance, and which ear hears it first tells it direction.

Step 2 of 5

The calls are too high for you.

Bat calls are usually far above the top of human hearing, which is useful: short, high sounds bounce cleanly off small things. A low, long note would flow straight past a moth.

Step 3 of 5

It shouts faster as it closes in.

Cruising, a bat calls a few times a second. Closing on prey, the calls come in a buzz dozens of times a second, so its picture of the target refreshes fast enough to catch a swerving insect.

Step 4 of 5

It is not a bird, and it really flies.

A bat's wing is a hand. The bones inside are fingers, stretched enormously long with thin skin between them — so a bat is the only mammal that flies rather than glides.

Step 5 of 5

Moths fight back.

Many moths grew ears tuned to exactly the pitch of bat calls. Hear one and the moth drops out of the sky; some even click back, jamming the bat's picture with noise.

Not every bat hunts insects. Most large bats eat fruit, find it by smell and sight, and do not echolocate at all.