UNDERWATER HEARING OF MARINE MAMMALS 



Behavioral underwater audiograms have been made for the bottlenose dolphin, Tursiops 

 truncatus (ref 28), the harbor porpoise, Phocoena phocoena (ref 29), the killer whale, Orcinus 

 orca (ref 30), the white whale, Delphinapterus leucas (ref 3 1 ), and the Amazon river dolphin, 

 Inia goeffrensis (ref 32). Audiograms for the bottlenosed dolphin, the killer whale, the har- 

 bor porpoise and the white whale are shown in figures 7 and 8. 



Underwater audiograms also have been made for four species of pinnipeds: the Cali- 

 fornia sea lion, Zalophus californianus (ref 33), the harp seal, Pagophilus groenlandicus (ref 

 34), the ringed seal, Pusa hispida (ref 35), and the harbor seal, Phoca vitulina (ref 36). 

 Figure 9 shows the underwater audiograms for these four species. 



Electrophysiological audiograms have been made for both cetaceans and pinnipeds. 

 Bullock et al (ref 1 2) tested anesthetized animals, including the striped dolphin, Stenella 

 coeruleoalba. the spotted dolphin, Stenella attenuata, the rough-toothed dolphin, Steno 

 bredanensis, and the Pacific bottlenosed dolphin, Tursiops gilli. Interspecific sensitivities 

 were similar and resembled the behavioral audiogram for Tursiops truncatus (ref 28). Evoked 

 potentials were used to determine an audiogram for an unrestrained, alert grey seal, Hali- 

 choerus grypus (ref 37). 



Figures 7 through 9 show underwater audiograms for eight species of marine mammals. 

 The data shown in these figures indicate that the marine mammals tested were relatively insensi- 

 tive at low frequencies. Most underwater threshold experiments have been conducted in small 

 tanks that introduced serious measurenent problems because of the sound field in the tank 

 (ref 38). Consequently, the low freque jy thresholds for marine mammals have not been 

 documented adequately. 



" Naval Ordance Test Station TP 4178, Aud tory Thresholds in the Bottlenose Porpoise, Tursiops truncatus, 

 by CS Johnson, p 22, 1966. 



~ Andersen, S, Auditory Sensitivity in the h :■ bor Porpoise, Phocoena phocoena, In: Investigations on 

 Cetacea, Vol 2, G Pilleri, ed, p 255-258, 1970. 



Hall, JD and CS Johnson, Auditory Threshold of a Killer Whale, Orcinus Orca, J Acous Soc Amer, 41(1), 

 p 515-517, 1971. 



-^ Hubb Sea Work Research Institute Technical Report 78-109, Auditory Thresholds of Two Beluga Whales 

 (Delphinapterus leucas), by MJ White, JC Norris. DK Ljunblad, KS Baron and GN DeSciara. p 13. 1978. 



"3 



Jacobs, DW and JD Hall, Thresholds of a Freshwater Dolphin, Inia geoffrensis, J Acous Soc Amer, 51(1), 

 p 530-533, 1972. 



Schusterman, RJ, RF Balliet and J Nixon. Underwater Audiogram of the California Sea Lion by Condi- 

 tioned Vocalization Techniques, J Exp Anal Beh. 17, p 339-350, 1972. 



Terhune, JM and K Ronald, The Harp Se-dl, Pagophilus groenlandicus. III, The Underwater Audiogram, 

 Can J Zool, 50, p 565-569, 1975. 



■^ Terhune, JM and K Ronald, Underwater Hearing Sensitivity of Two Ringed Seals (Pusa hispida). Can J 

 Zool, 53, p 227-231, 1975. 



■^^.Mohl, B, Auditory Sensitivity of the Common Seal in Air and Water, J Aud Res, 8, p 27-38, i968. 



37 



Ridgway, SH and PL Joyce, Studies on Seal Brain by Radiotelemetry, In: Biology of the Seal, K Ronaid 



and AW Mansfield, eds, p 81-91, 1975. 



38 



Parvulescu, A, The Acoustics of Small Tanks. In: Marine Bioacoustics, WN Tauolga, ed, p 7-13, Pergam- 



mon Press, 1967. 



H-16 



