CUMMINGS ET AL.: SOUND FROM BRYDE AND FINBACK WHALES 



son and Friedl (1982), working off Hawaii, recorded 

 them only from the end of August to late April. Nor- 

 throp et al. (1968), in the North Pacific, noted them 

 from October to March. Finally, in recordings from 

 finbacks in March 1985 (Gulf of California) typical 

 20-Hz short pulses were the predominant sound 

 (Thompson et al. 6 ). Like the well-known songs of 

 humpback whales, these sounds are probably a 

 manifestation of social or other behavior which oc- 

 curs seasonally. According to Watkins (1981) they 

 "perhaps were a courtship or reproductive display". 

 Watkins and others apparently have not noted our 

 frequently recorded 68-34 Hz long moans. 



There have been many technical advances in bio- 

 acoustic signal acquisition and processing. Long- 

 term recordings can be used for obtaining informa- 

 tion about certain behaviors, presence or absence of 

 animals, or perhaps distribution of a given species, 

 without the presence of an observer (Cummings et 

 al. 1983). Great gains are being made in the field of 

 sighal processing wherein computer- and optically 

 aided automatic acoustic pattern recognition is possi- 

 ble for a number of sounds with recognizable 

 physical criteria. However, regardless of technical ad- 

 vances, the use of such tools is severely limited 

 without first knowing the behavioral significance of 

 the animal sound production. In reality, the two are 

 mutually dependent. An analogous situation would 

 be the use of the most refined instrumentation 

 available for listening in on a conversation carried 

 out in a foreign language that is unfamiliar to the 

 observer. Although extremely difficult to fulfill, the 

 need for related behavioral information on finback 

 whales is paramount. 



For these and other reasons, descriptions of sounds 

 from identified sources should be given in detail 

 along with adequate description of the recording in- 

 struments. Recording procedures and analyses can 

 greatly affect the apparent variability of sounds. 

 Moreover, one must be careful to consider the large 

 variety of sounds that is apparent in any species of 

 marine mammal (including the finback whale, as 

 shown in this report) and the relatively limited 

 number of recorded sounds of any species. 



ACKNOWLEDGMENT 



The authors thank R. S. Gales for assisting in the 

 field observations; D. R. Nelson for assisting in the 



"Thompson, P. 0., L. T. Findley, and 0. Vidal. Finback whale 

 underwater sounds recorded near Guaymas, Mexico. Manuscr. in 

 prep. Paul 0. Thompson, 4256 Sierra Vista, San Diego, CA 92103. 



diving and other field work; R. Ludwig and crew for 

 operating the ship; W. A. Watkins and W. E. Schevill 

 for comments on the research; and M. Richardson, 

 R. Hawley, and T Rydlinski for producing the 

 finished manuscript. This work was supported by 

 funds for Independent Research (Naval Ocean 

 Systems Center) and by the Office of Naval Research 

 (R. C. Tipper and B. Zahuranec) by means of con- 

 tracts with the San Diego Society of Natural History 

 and Scripps Institution of Oceanography. 



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