Letters

MARINE MAMMAL SCIENCE, 19(1):607-608 (July 2003) 0 2003 by the Society for Marine Mammalogy

WHEN ATTACKING THEIR PREY SPERM WHALES ARE UPSIDE DOWN

In a carefully balanced account Fristrup and Harbison (2002) have recently discussed two hypotheses to explain the feeding strategy of sperm whales. In their Abstract they summarize: “The first hypothesis postulates that sperm whales locate their prey visually, either silhouetted against the midwater ‘sky’ or by searching for bioluminescence pro- duced by the movements of their prey. The second hypothesis postulates that sperm whales create a zone of stimulated bioluminescence around the mouth which attracts squid and other visual predators . . .. If sperm whales search for silhouetted prey, they should be orientated upside-down to improve visual coverage and to facilitate the transi- tion from search to prey capture . . ..” The authors discuss the possibility of this upside- down approach at some length but they offer no evidence to support it. In their text they include a paper by Clarke et al. (1988) among other authors who have published on food and feeding in the sperm whale, but they do not mention that in Clarke at ul. (1988), pp. 106-109 and figure 14, there is definite evidence that the sperm whale is upside down when attacking its prey. We here summarize that evidence and discuss its signifi- cance, believing that this will lend more perspective to Fristrup and Harbison’s account.

The evidence arose from an observation, unpublished until 1988, made when, during the Antarctic whaling season 1947-1948, the first author was serving as Whale Fishery Inspector on board F1. E Southern Harvester where he also conducted a research program for the Discovery Investigations of the British Colonial Office.

On 7 January 1948 in position 63”31’S, 78’16’E he found a very large nototheniid fish in the stomach of whale SH440, a male sperm whale 14.6 m long. This fish, later identified as Dkrostichus mwsoni Norman 1937, is now preserved in the British Museum (Natural History). It measured 1.23 rn and weighed 30 kg. According to Andriashev (1 968) large individuals of Dissostzchza are believed to be bathypelagic in habit. On the back of the first author’s specimen there were three, possibly four, wounds caused by the sperm whale’s teeth. They could not have been caused by the small, slightly projecting and recurved teeth sometimes found on the edges of tooth-sockets in the sperm whale’s upper jaw. By the time the first author had measured the distance between the tooth wounds, whale SH440 had been cleared from the deck, but a week later he measured the distances between adjacent and opposite teeth of another sperm whale of about the same size, 15.4 m, and between one-half and two-thirds of the way up the lower jaw. The dis- tances between the wounds and the teeth agreed neatly. So unless the fish was swimming on its back, which is most unlikely, sperm whale SH440 was upside down when it seized the fish.

Over the years there have accumulated other indications, reviewed by Clarke et uf. (1988), that the sperm whale turns over to attack its prey. About 330 B.C. Aristotle said, in his Historia Animafium, Book 3 , that sharks, dolphins, and whales roll over when seiz- ing their prey because in these animals the mouth is ventral (Budker 1971, p. 96). In the days of open boat whaling Bennett (1840, 11, p. 176) said a sperm whale was always upside-down when it attacked to bite a whaleboat. Caldwell et al. (1966, p. 691) searched

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the narratives of nineteenth century whaling and found that sperm whales usually, though not invariably, turned over when about to bite a whaleboat. The behavior extends to in- traspecific fighting in sperm whales (Clarke and Palita, 1988) because Hopkins (n.d.) watched a fight between rival bulls and saw how one, charging the other, turned over when about a hundred feet away.

The first author’s observation aboard the Soutbwn Harvester in 1948 goes far to answer Scamrnon’s rhetorical question (1874, p. 83) “when the creature [sperm whale] essays to grasp a large object on the water, it instantly rolls over to bite, but does it necessarily follow that the same attitude must be maintained when obtaining its food in the abyss beneath?” However, we cannot know all that goes on in the dark of the sea, and the sperm whale may sometimes use other stratagems to capture its prey like those discussed in the second hypothesis of Fristrup and Harbison (2002).

LITERATURE CITED

ANDRIASHEV, A. P. 1968. The problem of the life community associated with the Antarc- tic fast ice. Pages 147-155 in SCAR Symposium on Antarctic Oceanography, Santia- go, Chile, 13-16 September 1966. Scott Polar Research Institute, Cambridge.

BENNETT, F. D. 1840. Narrative of a whaling voyage round the globe, from the year 1833 to 1836. London, Richard Bentley. 2 vols: pp xvi, 402; viii, 395.

BUDKER, P. 1971. The life of sharks. Columbus University Press, New York, NY. CALDWELL, D. K., M. C. CALDWELL AND D. W. RICE. 1966. Behavior of the Sperm Whale,

Physeter catodon L. Pages 677-717 in K. S. Norris, ed. Whales, dolphins and por- poises. University of California Press, Berkeley and Los Angeles, CA.

CLARKE, R., AND 0. PALIZA. 1988. Instraspecific fighting in sperm whales. Report of the International Whaling Commission 38:235-241,

CLARKE, R., 0. PALIZA AND A. AGUAYO L. 1988. Sperm whales of the Southeast Pacific. Part IV. Fatness, food and feeding. Investigations on Cetacea, Berne, 21:53-195.

FRISTRUP, K. M., AND G. R. HARBISON. 2002. How do sperm whales catch squids? Ma- rine Mammal Science 18:42-54.

HOPKINS, W. J. n.d. She blows! And sparm at that! London, Constable & Co. Limited. (The American edition was dated 1922).

SCAMMON, C. M. 1874. The marine mammals of the north-western coast of North Arneri- ca, described and illustrated: Together with an account of the American whale fish- ery. San Francisco: John H. Carrnany and Company. G. P. Putman’s Sons, New York, NY.

ROBERT CLARKE AND OBLA PALIZA, Apartado 40, Pisco, Peru; e-mail: robertclarke007@ hotrnail.com.

MARINE MAMMAL SCIENCE, 19(1):608-612 (July 2003) 0 2003 by the Society for Marine Mammalogy

DIGITAL PHOTOGRAPHY IMPROVES EFFICIENCY OF INDIVIDUAL DOLPHIN IDENTIFICATION: A REPLY TO MIZROCH

We agree with Dr. Mizroch that the absolute resolution of film is higher than that of digital images. One need look no farther than the camera specifications published by Ni- kon, Canon, Kodak, and others to confirm this fact. However, the purpose of our note was not to examine the absolute resolution of the two media. In fact, we opted not to