Marine Mammals: Hearing and Echolocation at Coconut Island

• Main Author: Nachtigall, Paul E
• Other Authors: HAWAII INST OF MARINE BIOLOGY KAILUA HI MARINE MAMMAL RESEARCH PROGRAM
• Format: Text
• Language: English
• Published: 2011
• Subjects: Biology; Anatomy and Physiology; Test Facilities; Equipment and Methods; Acoustics; *AUDIOMETRY; *ECHO RANGING; *HEARING; *SONAR ECHOES; *UNDERWATER ACOUSTICS; *WHALES; AMPLITUDE MODULATION; AUTOMATIC GAIN CONTROL; BASE LINES; DOLPHINS(MAMMALS); MEASUREMENT; PORPOISES; *BEAKED WHALES; *ECHOLOCATION; *AUDIOGRAMS; *AUDITORY EVOKED POTENTIALS; STRANDED ANIMALS; AEP(AUDITORY EVOKED POTENTIALS); KILLER WHALES; Killer Whale
• Online Access: http://www.dtic.mil/docs/citations/ADA599978; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA599978

The ability to obtain hearing data on new species requires opportunistic motivated action. A permit from the NMFS to test the hearing of stranded animals, and to keep in touch with the stranding networks in the United States allows us opportunities for testing stranded animals when they become available. Animals in public display facilities also occasionally become available for hearing examination, especially if the audiometric tests are conducted for short periods of time, like those for AEP measures. The AEP measures also can be used on boats so that temporarily caught animals can be tested. All of these approaches allow us to increase the species and the number of animals tested. We work closely with Alexander Ya. Supin from the Russian Academy of Sciences to test the hearing of new species of animals, especially those that require a new technique or adaptations to new procedures. We primarily use the envelope following response (EFR) auditory evoked potential approach in which we present amplitude modulated sounds to the animals and monitor the brain wave patterns in response to the amplitude modulation rate. We measured the audiogram of a stranded beaked whale and showed that its best hearing was the same as its published echolocation return frequencies at 40 to 50 kHz. We continued the measurement of hearing during echolocation on the false killer whale, demonstrating the ability of the whale to change hearing during echolocation. We completed comparative measurements of hearing during echolocation on the bottlenose dolphin and the harbor porpoise. Both demonstrated control of hearing in a manner similar to the false killer whale. We then examined whether or not there were additional automatic gain control mechanisms in the hearing of the false killer whale during echolocation. We also tested the comparative hearing pathways of the bottlenose dolphin and the false killer whale.