Echolocation in dolphins and bats

Research on animal sonar can be traced to the Italian scientist Lazzaro Spallanzani, who in 1773 observed that bats could fly freely in a dark room and that blind bats could fly and avoid obstacles as well as bats that could see. Five years later Swiss scientist Charles Jurine found that when the ears of bats were plugged with wax, the animals became helpless and collided with obstacles. That early work took place before the understanding of the principles of ultrasonics and the establishment of acoustics as a science. So Spallanzani and Jurine could not formulate an acoustic theory of biosonar. It was not until 1938 that Robert Galambos and Donald Griffin used an ultrasonic detector developed by William Pierce to show that bats echolocated by emitting ultrasound and receiving the echoes. By that time the principles of ultrasonics were understood, and they provided a theoretical framework for describing the acoustic process underlying echolocation. Thus began modern research into animal sonar as described in Griffin's seminal book Listening in the Dark: The Acoustic Orientation of Bats and Men (Yale University Press), originally published in 1958. © 2007 American Institute of Physics.