Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 406-417. 



Hearing and acoustic orientation in marine animals* 



By Donald R. Griffin 

 Biological Laboratories, Harvard University, Cambridge, Mass. 



Summary — The evidence that underwater sound is important in the behaviour of fishes and cetaceans 

 is reviewed, with emphasis on the possible occurrence of acoustic orientation. Both these groups of 

 marine animals have now been shown to have excellent hearing. At least one fish has a minimum 

 auditory threshold of the same order of magnitude as the typical human threshold at 2000-4000 

 c.p.s. (about 10"i® watt/cm^ energy flux). Porpoises can hear sounds of moderate intensity at fre- 

 quencies well above 100 kc. A series of recordings which may have resulted from a deep sea fish 

 engaged in echo-sounding are analyzed and discussed, and the possible role of echolocation in marine 

 animals is compared with the available evidence of its nature and occurrence in bats and other 

 animals relying on airbourne sound. In this connection the possible usefulness of continuous sounds 

 and standing wave patterns is discussed with reference to the observed fact that a low frequency 

 sound in a small tank undergoes marked fluctuations in intensity over distances that are a small 

 fraction of its wave-length in water. 



In recent years it has become widely recognized that a variety of sounds are pro- 

 duced by animals living in the ocean. The chief cause of this increased awareness 

 has been the use of improved devices for listening to sounds in water. It had been 

 known since the time of Aristotle that some fish produce sounds (for recent pre-war 

 studies see Tower, 1908; Burkenroad, 1931; Dijkgraaf, 1932; and Hardenberg, 

 1934). But the unaided human ear is at a great disadvantage in hstening to underwater 

 sounds, and hence only those of considerable intensity can be heard without devices 

 to provide us with a sensitivity to sound waves in water that approaches our sensi- 

 tivity for sounds arriving through the air. Such devices have been developed primarily 

 for miUtary purposes, and it was during the second World War that sounds of fish 

 and other marine animals first aroused serious concern when they interfered with 

 underwater hstening operations. Surveys were therefore undertaken to determine 

 the sources and seasonal occurrence of the more intense of these biological noises 

 (LoYE and Proudfoot, 1946; Dobrin, 1947; Knudsen, Alford, and Emling, 

 1948). Since the war such surveys have continued on a broader basis with greater 

 attention to their biological significance (Johnson, Everest, and Young, 1947; 

 Johnson, 1948; Fish, Kelsey, and Mobray, 1952). 



As a result of these studies it is now clear that sounds of considerably greater inten- 

 sity than the ambient background noise level of the ocean are commonly produced 

 by three major groups of animals: (1) many species of fish, (2) several species of 

 marine mammals — certainly some of the smaller whales and porpoises and perhaps 

 some of the larger whales as well, and (3) the snapping shrimps of the genera Crangon 

 and Synalpheus among the Crustacea. Too little is known about the significance of 

 the " snap " of these shrimps to warrant any discussion of it, and indeed the one 

 serious study to date has led to the conclusion that the noise may well be incidental 

 to some other function of these animals' highly modified claws (Johnson, Everest, 



* Contribution No. 789 from the Woods Hole Oceanographic Institution. 



406 



