THE DIET OF STRAP-TOOTHED WHALES (MESOPLODON LAYARDII)

The food habits of strap-toothed whales (Mesoplodon layardii) were exa mined in detail using stomach contents from 14 stranded whales found o n South African and New Zealand coasts. Although a few unidentified fi sh otoliths and crustacean remains were found in two of these stomachs , 24 species of oceanic squids (some of which occur at a great depth) accounted for 94.8% of counted prey items (n = 232). Histioteuthis sp. and Taonius pavo were the predominant prey species (25.0 and 17.2% by number, 21.4 and 19.9% by mass, respectively). The presence of sub-An tarctic squid species suggested a northward migration to South African waters in late summer/autumn. Prey sizes were compared between males with fully grown strap-teeth and. females/immature males without erupt ed teeth, using dorsal mantle lengths (DML) and weights of squids esti mated from beak measurements. Although females/immature males ate long er squids than males, there was no significant difference in the estim ated weights of squids eaten by the two groups. The presence of fully- erupted teeth in adult males, therefore,did not seem to influence the size of prey ingested, even though an adult male could only open its j aws about half as wide as a female. In general, the sizes of cephalopo ds eaten by strap-toothed whales were not significantly different from those eaten by smaller odontocetes, such as spotted dolphins and dwar f sperm whales, but were significantly smaller than those eaten by lar ger odontocetes, such as false killer, long-finned pilot, Cuvier's bea ked, and southern bottlenose whales.