echolocation
Animals such as bats and dolphins send out ultrasound waves and use their echoes, or reflected waves, to identify the locations of objects they cannot see. This is called echolocation. Animals use echolocation to find prey and avoid running into objects in the dark. You can see in the Figure below and also at the following URL how a bat uses echolocation to find insect prey. http://www. bsos. umd. edu/psyc/batlab/headaimmovies/nsf_challenge/nsf4. wmv.