The Risso’s dolphin (Grampus griseus) is an exclusively cephalopod-consuming delphinid with a distinctive vertical indentation along its forehead. To investigate whether or not the species echolocates, a female Risso’s dolphin was trained to discriminate an aluminum cylinder from a nylon sphere (experiment 1) or an aluminum sphere (experiment 2) while wearing eyecups and free swimming in an open-water pen in Kaneohe Bay, Hawaii. The dolphin completed the task with little difficulty despite being blindfolded. Clicks emitted by the dolphin were acquired at average amplitudes of 192.6 dB re 1 μPa, with estimated sources levels up to 216 dB re 1 μPa-1 m. Clicks were acquired with peak frequencies as high as 104.7 kHz center frequencies as high as 85.7 kHz 3-dB bandwidths up to 94.1 kHz and root-mean-square bandwidths up to 32.8 kHz Click durations were between 40 and 70 μs. The data establish that the Risso’s dolphin echolocates, and that, aside from slightly lower amplitudes and frequencies, the clicks emitted by the dolphin were similar to those emitted by other echolocating odontocetes. The particular acoustic and behavioral findings in the study are discussed with respect to the possible direction of the sonar transmission beam of the species.
Echolocation in the Risso’s dolphin, Grampus griseus
Jennifer D. Philips, Paul E. Nachtigall, Whitlow W. L. Au, Jeffrey L. Pawloski, Herbert L. Roitblat; Echolocation in the Risso’s dolphin, Grampus griseus. J. Acoust. Soc. Am. 1 January 2003; 113 (1): 605–616. https://doi.org/10.1121/1.1527964
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