Underwater audiogram of a Hawaiian monk seal (Monachus schauinslandi)

Underwater audiograms are available for a few pinnipeds from the families otariidae and phocidae, but little is known about hearing abilities in the monachid seals. A young male Hawaiian monk seal (Monachus schauinslandi) was trained at Sea Life Park on Oahu, Hawaii for an underwater hearing test using a go/no‐go response paradigm. Over a 6‐month period, auditory thresholds from 2 to 48 kHz were measured using an up/down staircase psychometric technique. The resulting audiogram shows a somewhat narrower hearing range than for other pinnipeds. The monk seal’s hearing was most sensitive (20 dB above maximum sensitivity) between 12 and 28 kHz. Below 8 kHz, the Hawaiian monk seal’s hearing was less sensitive than other pinnipeds measured. High‐frequency sensitivity dropped off sharply above 30 kHz, as has been reported for other otariids, Callorhinus and Zalophus. Phocid seals, Phoca hispida, P. groenlandica, and P. vitulina, have a broader hearing range with the upper limit near 60 kHz.