Animal echolocation

Echolocation, also called bio sonar, is the biological sonar used by several kinds of animals. Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects. Echolocation is used for navigation and for foraging (or hunting) in various environments.

Echolocating animals include some mammals and a few birds; most notably microchiropteran bats and (toothed whales and dolphins), but also in simpler form in other groups such as shrews, one genus of megachiropteran bats (Rousettus) and two cave dwelling bird groups, the so-called cave swiftlets in the genus Aerodramus (formerly Collocalia) and the unrelated Oilbird Steatornis caripensis.

The term echolocation was coined by Donald Griffin, whose work with Robert Galambos was the first to conclusively demonstrate its existence in bats in 1938. As Griffin described in his book, the 18th century Italian scientist Lazzaro Spallanzani had, by means of a series of elaborate experiments, concluded that bats navigate by hearing and not by vision. In 1912, Sir Hiram Maxim had independently proposed that bats used sound below the human auditory range to avoid obstacles. In 1920, the English physiologist Hartridge proposed instead that bats used frequencies above the range of human hearing, which ultimately proved to be the case

Echolocation in was not properly described until two decades after Griffin and Galambos' work, by Schevill and McBride.

Echolocation is the same as active sonar, using sounds made by the animal itself. Ranging is done by measuring the time delay between the animal's own sound emission and any echoes that return from the environment. The relative intensity of sound received at each ear as well as the time delay between arrival at the two ears provide information about the horizontal angle (azimuth) from which the reflected sound waves arrive.

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