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African Journal of Marine Science

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Food and feeding of sperm whales physeter macrocephalus off the west coast of South Africa

PB Best

Abstract


The stomach contents of 1 268 sperm whales Physeter macrocephalus processed at the Donkergat whaling station, South Africa, were examined during the 1962 and 1963 whaling seasons. Results were compared with
Clarkefs analysis of cephalopod beaks collected in 1963 (Clarke 1980). There was no significant difference in the incidence of food in the stomachs between whales taken in the morning (07:15.11:15), at midday (11:15.15:15) or in the afternoon (after 15:15). The incidence of food remains was less in medium-sized (12.2.13.7 m) and large (.14 m) males than in small (.11.9 m) males and females, and their stomachs more frequently contained the beaks of cephalopod species from the Antarctic or subAntarctic. These phenomena were related to a winter migration of medium-sized and large males into the whaling ground from south of the Subtropical Convergence. Medium-sized and large males fed more frequently on larger species of endemic cephalopods than females or
small males, whereas males in general ate larger individuals of a cephalopod species than females. Because larger and older individuals within a cephalopod species are frequently distributed deeper than other individuals, males may feed lower in the water column than females. Evidence from catch positions and the incidence of non-cephalopod prey items suggests that some males within the West Coast whaling ground moved into the continental slope water (200.1 000 m deep), where they dived to the sea floor and took benthic organisms such as rajids, crabs, Lophius sp. and Allocyttus sp. Females stayed farther offshore, where both sexes fed mesopelagically, consuming mesopelagic-bathypelagic cephalopods, Ruvettus sp., mysids and ceratids. Some of the differences
in distribution and feeding behaviour between males and females may reflect adaptations to the social organization of the species.



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