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spyhop_deeckeResident and transient forms of killer whales exhibit striking differences in their diet. While residents feed exclusively on Pacific salmon (Oncorhynchus spp.), transients only feed on warm-blooded prey – marine mammals in most cases, with the occasional seabird on the menu. In addition, dietary preference varies between different transient populations that choose to feed on different marine mammal species.

By following groups of transients, using acoustic monitoring to record their every kill, attack, and harassment of marine mammals, we are able to acquire a better understanding of the diet composition of the different killer whale populations off the coast of Alaska and British Columbia. This, in turn, will allow us to determine the impact of killer whale predation on marine mammal populations, and to delineate the role of killer whales in the North Pacific ecosystem with greater accuracy.

The following table demonstrates what studies of the dietary preference of transient populations in various locations have revealed so far:

Transient type Principal diet % of Steller attacks observed Research team

British Columbia West Coast Transients Harbor seals. Steller sea lions make up only a small proportion (7%) of the diet. Grey and minke whales are occasionally killed 7% John Ford
Graeme Ellis
Lance Barrett-Lennard, Volker Deecke

Southeast Alaska West Coast Transients Harbor seals, despite a greater preference (17% of recorded kills) for Steller sea lions 17% Jan Straley, Dena Matkin and Volker Deecke

Prince William Sound AT1 Harbor seals and Dall’s porpoises none observed Craig Matkin

Gulf of Alaska Gulf of Alaska Steller sea lions 79% Craig Matkin and Lori Mazzucca

Aleutian Islands ? Minke, grey and humpback whales and
northern fur seals
none observed Lance Barrett-Lennard and Craig Matkin



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