Kangaroo Rat Auditory Thresholds before and after Middle Ear Reduction

Abstract

Four kangaroo rats were conditioned by shock avoidance and their auditory thresholds determined from 125 through 8,000 Hz. The middle ears were reduced and thresholds re-determined. Normal mean thresholds range from about 9 dB at 1,000 Hz, to 21 dB at 125 Hz and 19 dB at 8,000 Hz. At 1,000 Hz and below, volume reduction causes a loss of 10 dB or more in sensitivity. The method is described and its difficulties discussed. The importance to kangaroo rats of low- rather than high-frequency sensitivity, and the proposed role of the middle ear cavity, are also discussed.