Perception of Distance in Animal Echo-Location

Abstract

THE frequency sweep used by some bats is unlikely to be essential for distance perception by these animals, and is possibly no more than an accidental consequence of their method of sound production. When the cricothyroid muscles of the larynx of Eptesicus bats are denervated the modulation is altogether absent and the frequency becomes constant at about 10 kc. Yet such bats land normally on walls and avoid obstacles of moderate size. A slight decline in performance can be attributed to the greater wave-length used and the reduced vigour of the bats as a result of the surgical operation¹.