Cardiac responses to acoustic playback experiments in the captive bottlenose dolphin (Tursiops truncatus)

Acoustic recordings were used to investigate the cardiac responses of a cap tive dolphin (Tursiops truncatus) to sound playback stimuli. A suction-cup hydrophone placed on the ventral midline of the dolphin produced a continuo us heartbeat signal while the dolphin was submerged. Heartbeats were timed by applying a matched-filter to the phonocardiogram. Significant heart rate accelerations were observed in response to playback stimuli involving cons pecific vocalizations compared with baseline rates or tank noise playbacks, This method documents that objective psychophysiological measures can be o btained for physically unrestrained cetaceans. In addition, the results are the 1st to show cardiac responses to acoustic stimuli from a cetacean at d epth. Preliminary evidence suggests that the cardiac response patterns of d olphins are consistent with the physiological defense and startle responses in terrestrial mammals and birds.