Hearing in the elephant ( Elephas maximus )

Abstract

The auditory sensitivity of a 7-year old female Indian elephant was determined using a two-choice procedure. The animal was trained to initiate a trial by pressing a “center” button and was rewarded with flavored sugar water for pressing a button to its left if a tone was presented or for pressing a button to its right if no tone was presented. The elephant proved to be quite sensitive to low-frequency tones and could hear as low as 16 kHz at 65 dB SPL. The frequency of best hearing was 1 kHz at which the animal's threshold was 8 dB. However, the elephant proved insensitive to high-frequency tones and was unable to hear above 12 kHz at which frequency its threshold was 72 dB. The high-frequency hearing ability of the elephant is the poorest of any mammal yet tested and the failure of the elephant to hear much above 10 kHz demonstrates that the inverse correlation between head size (i.e., interaural distance) and high-frequency hearing ability is valid even for the largest of terrestrial mammals. Furthermore, this finding indicates that humans can no longer be considered unique among mammals for their inability to hear above 20 kHz. Instead, it appears that the upper limit of human hearing is a consequence of our relatively large size and not the result of any special adaptation for the reception of speech sounds. [Work supported by NSF grant BNS 78-07391 and NIH grant HD 02528.]