Introduction
The position of the killer whale (Orcinus orca) at the top of the marine trophic pyramid is unquestioned. It consumes a remarkable variety of organisms, ranging in size from small schooling fish to blue whales (Balaenoptera musculus) and as taxonomically diverse as seabirds (ducks and alcids; Bloch and Lockyer 1988), marine reptiles (leatherback turtles, Dermochelys coriacea; Caldwell and Caldwell 1969), elasmobranchs (Fertl et al. 1996; Visser 1999a), and terrestrial mammals as they swim across coastal channels (e.g., cervids; Dahlheim and Heyning 1999). If killer whales have any natural predators, these would be other killer whales, as there is some evidence to suggest “cannibalism” (Shevchenko 1975; but see Pitman and Ensor 2003).