As demonstrated by several literature reports on 

 killer whale predatory activities (Martinez and 

 Klinghammer 1970; Steiner et al. 1979; Tarpy 1979; 

 Smith et al. 1981), their hunting techniques are 

 characterized by highly developed group coordina- 

 tion. It appears that those attacks involving imma- 

 ture killer whales, in some cases calves (Baldridge 

 1972; Cummings et al. 1972), are part of a complex 

 learning behavior in which individuals increase and 

 strengthen their individual and group hunting capa- 

 bilities (described for pinniped hunting by L6pez and 

 L6pez 1985). 



Furthermore, Jonsgard (1968) concluded that, 

 under "normal" conditions, it is very difficult for 

 killer whales to kill baleen whales and other large 

 cetaceans that are in good health. He based his con- 

 clusions on the absence of such reports during many 

 years of Norwegian whaling in the northeastern 

 North Atlantic. Several authors have provided evi- 

 dence, in some cases circumstantial, to support 

 Jonsgard's hypothesis, and it is not surprising that 

 most of these observations have to deal with those 

 relatively more accessible coastal species of baleen 

 whales. For example, Andrews (1914) indicated that 

 many gray whales taken commercially were found 

 to survive killer whale attacks, as evidenced by 

 damaged tongues, flippers, and other parts of the 

 body. Rice and Wolman (1971) reported that 57 

 (18%) of 316 gray whales collected in California 

 under scientific permit, showed evidence of having 

 been attacked by killer whales (e.g., tooth marks on 

 flukes and flippers), and concluded that this indi- 

 cates a fairly high frequency of unsuccessful attacks. 

 Morejohn (1968) observed an unsuccessful attack by 

 seven killer whales on three gray whales, including 

 a female with a calf. Cummings et al. (1972) de- 

 scribed the unsuccessful attack of five killer whales 

 on two southern right whales, ending after 25 min- 

 utes with no signs of blood or other evidence of 

 physical harm. As pointed out by Jonsgard (1968), 

 the attack on a minke whale reported by Hancock 

 (1965), was on an animal "trapped" by low tide in 

 a small and shallow bay and was therefore an easy 

 prey. The blue whale wounded off Baja California, 

 Mexico, (Tarpy 1979) was immature and was at- 

 tacked by about 30 killer whales (including several 

 mature males). Our observation on the apparently 

 unsuccessful attack on fin whales provides additional 

 evidence to support Jonsgard's (1968) conclusion. 



Observations on at least three species of cetaceans 

 known to be preyed upon by killer whales, gray 

 whales, humpback whales, and white whales, Del- 

 phinapterus leucas, show that they sometimes re- 

 main completely motionless in the presence of killer 



whales (Kellogg 1940; Hubbs 1965; Tomilin 1967; 

 Baldridge 1972), probably in order to avoid detec- 

 tion. After a series of underwater sound playback 

 experiments, Cummings and Thompson (1971) con- 

 cluded that gray whales recognize the voice of killer 

 whales, that they can easily localize the sounds 

 underwater, and that they flee killer whale vocaliza- 

 tions. Such avoidance, according to these research- 

 ers, involves several behaviors, e.g., sound local- 

 ization, silence, and reduced exposure (including 

 invisible and non-audible blows), that appear to func- 

 tion as protective mechanisms. Similar underwater 

 acoustical experiments carried out by Fish and 

 Vania (1971) with white whales showed similar pro- 

 tective responses in the presence of killer whales 

 sounds. 



As noted previously, while the three killer whales 

 were harassing the pair of fin whales, at least six 

 high whistling sounds were audible. These killer 

 whale sounds possibly correspond to the "whistles" 

 (tonal vocalizations) or "screams" (pulsed vocaliza- 

 tions) recorded during cooperative feeding behavior 

 by Steiner et al. (1979). We apparently detected the 

 killer whales visually before the pair of fin whales 

 were aware of them, and possibly the killer whales 

 were silent before the attack in order to avoid 

 detection. 



Acknowledgments 



We thank G. Rojo for his help in the field. M. E. 

 Hatziolos (U.S. Agency for International Develop- 

 ment, Washington, D.C.) made available to us much 

 of the literature on killer whale attacks, and E. 

 Pfeiler (Department of Biology, University of 

 Puerto Rico, Mayagiiez), B. Wiirsig (Moss Landing 

 Marine Laboratories, Moss Landing, CA), and L. T. 

 Findley (ITESM-Campus Guaymas) criticized the 

 manuscript and offered suggestions for its improve- 

 ment. 



Literature Cited 



Andrews, R. C. 



1914. Monographs of the Pacific Cetacea. I. The California 

 gray whale {Rhachianectes glaucus Cope). Mem. Am. Mus. 

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 Baldridge. A. 



1972. Killer whales attack and eat a gray whale. J. Mammal. 

 53:898-900. 

 Cummings, W. C, and P. 0. Thompson. 



1971. Gray whales. Eschrichtius robustus, avoid the under- 

 water sounds of killer whales, Orcinus orca. Fish. Bull., 

 U.S. 69:525-530. 



Cummings, W. C, J. F. Fish, and P. 0. Thompson. 



1972. Sound production and other behavior of southern right 



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