Auditory thresholds of a captive Eastern Pacific bottle-nosed dolphin, Tursiops spp

The hearing threshold of a bottle-nosed dolphin from the Eastern Pacific was tested using behavioral response techniques. The animal responded to signals ranging from 2 to 135 kHz, but did not respond to higher frequency signals (136-160 kHz) despite repeated trials. The range of greatest sensitivity was between 25 and 70 kHz with peak sensitivities at 25 and 50 kHz. This measured hearing threshold is compared to frequency responses and sensitivities previously reported for other cetaceans.