Echolocation

(biophysics) An animal's use of sound reflections to localize objects and to orient in the environment.

The biological sonar that bats, porpoises, and certain other animals use to navigate without the visual system. Such animals have evolved the ability to perceive objects by emitting sounds and hearing the echoes that the objects reflect to their ears. The locations and characteristics of the objects are represented by acoustic properties of the echoes, and the ears and auditory systems of these animals act as the sonar receiver. The sense of hearing is specialized for converting echo information into displays of objects, which are perceived as acoustic images that guide the animal's behavior. The best-known examples of echolocating animals are bats (Microchiroptera) and porpoises and toothed whales (Cetacea). However, several other kinds of mammals also can echolocate. See also Sonar.

Bats produce their ultrasonic sonar sounds from the larynx and broadcast them through the open mouth or through a specialized transmitting antenna formed around the nostrils. Porpoises produce their sonar sounds from structures located beneath the blowhole on the top of the head (through which they breathe) and project them into the water through the rounded, protuberant forehead, which contains acoustically specialized tissue. The sonar sounds of porpoises and whales are very brief impulses, or clicks, which contain a wide range of ultrasonic frequencies, all occurring at the same instant. The rate of emission of these sonar clicks depends in part upon the distance to objects that interest the animal, and can vary from several sounds per second to several hundred. Porpoises use their sonar to find fish and presumably to perceive objects beyond the relatively restricted range of vision under water. See also Chiroptera; Phonoreception; Ultrasonics.