Echolocation and Communication in Bats

Bat echolocation studies date back to 1793 when Lazaro Spallanzani investigated the effects of blinding and deafening bats. He blinded wild bats and several days after the operation found that they had survived and had insect-laden stomachs. The deafened bats, on the other hand, collided with obstacles in a darkened or lighted room (Dijkgraaf, 1960). Griffin & Galambos (1940, 1941 and 1942) as well as Dijkgraaf (1943, 1946) repeated some of Spallanzani\u27s experiments. They concluded that bats emit high frequency sounds, the echos of which are used for obstacle avoidance. Two essential kinds of observations supported the echolocation hypothesis: bats which had been deafened collided with vertical wires; bats produced sounds as they avoided obstacles and the nature of the sounds altered, depending on the difficulty of a particular flight maneuver