Cuvier’s beaked whales (Ziphius cavirostris) are distributed world-wide and are the most common cetacean to strand coincident with navy sonars. They are known for their extreme diving capabilities but diet information, fundamental to understanding foraging at depth, is limited from most regions. We report on 11,441 prey items from stomach contents of 16 stranded or by-caught specimens collected from 1976-2016 across the North Pacific. Overall diet included cephalopods, fish and crustaceans, but was dominated by cephalopods. Thirty-seven cephalopod species representing 16 families contributed 98.0% by number and 87.7% by mass. The Gonatidae (26.4% by number; 40.4% by mass), Octopoteuthidae (27.0% by number; 20.2% by mass) and Cranchiidae (27.2% by number; 10.7% by mass) families were dominant. Of these, the species Gonatopsis borealis represented 36.0% of the prey by mass and 13.2% by number with prey size (dorsal mantle length) ranging between 73 and 346 mm. Taonius borealis contributed 21.3% by number and 8.7% by mass with prey sizes between 107 and 443 mm. The majority of prey items (7,997) were from an adult male stranded in California which contained 20 species from 10 families of cephalopods and fishes. Regional variation was suggested by a higher incidence of crustaceans from whales in the western Pacific and fishes in the eastern Pacific, primarily represented by the giant grenadier. World-wide the most important cephalopod families in the diet of Cuvier’s beaked whales are Cranchiidae, Gonatidae, Histioteuthidae, Octopoteuthidae, Ommastrephidae, Onychoteuthidae, Pholidoteuthidae and Mastigoteuthidae, with Cranchiidae comprising important prey in all locations. While Gonatidae, Octopoteuthidae and Cranchiidae are the dominant prey in the North Pacific, Histioteuthidae and Cranchiidae are most important in the North Atlantic. Knowledge of diet composition can be used to understand how whales utilize their habitat, in calculating nutritional requirements, and may also help to define the locations of important foraging grounds.
Citation:
West, K., W. Walker, R. Baird, J. Mead, P. Collins. 2017. Diet of Cuvier’s beaked whales (Ziphius cavirostris) in the North Pacific and a comparison with their diet world-wide. Abstract (Proceedings) 22nd Biennial on the Biology of Marine Mammals, Halifax, Nova Scotia, October 22-27, 2017.