SUPERSONIC CRIES OF BATS

Abstract

THE recent discussion of bats in Nature^1,2 raises certain questions which I believe can be answered on the basis of new data resulting from a continuation of the investigations in which Dr. Robert Galambos and I were engaged before the War^3,4. The bat's ability to avoid obstacles depends upon a method of perception which I have called 'echo-location', or the location of objects by means of echoes⁵. The bats which we studied emit for this purpose short pulses of sound and hear the echoes which return from any solid object in their path. The emitted sound has a frequency of approximately 50 kilocycles per second, and hence is virtually inaudible to human ears. Many blind men also seem to use some form of echo-location based on audible sounds, for they can often detect obstacles at a distance, but lose this ability if their ears are stopped, or if they are distracted by loud noises⁶. Radar and the various underwater acoustic devices which locate distant objects by means of echoes are also examples of the general process of echo -location.