Underwater audiogram of the northern fur seal ( Callorhinus ursinus )

Abstract

In order to compare the underwater hearing of otariid and phocid pinnipeds, two feral, yearling females were tested in a “go/no-go” response procedure. Using a tracking procedure, 20 runs was the minimum number of runs for each threshold estimate. Audiograms for both seals were similar in shape and absolute threshold values. The range of maximal sensitivity for Callorhinus is between 2 and 28 kHz. Between 28 and 42 kHz there is a hearing loss of about 120 dB/octave, setting the high-frequency cutoff for this species at 40 kHz. These results are consistent with the idea that the major difference between the underwater bearing of the otariid and phocid pinnipeds is the high-frequency cutoff.