Differences in the Diet of Reproductively Isolated Ecotypes of Killer Whales (Orcinus orca Linnaeus, 1758) in the Seas of the Russian Far East

Abstract

A systematic analysis of the species composition of the prey of killer whale Orcinus orca Linnaeus, 1758 was carried out. The results of observations of killer whales hunting for different types of prey and the data from an analysis of the contents of their stomachs were summarized; the species affiliation of the prey was compared with the affiliation of predators to the R- or T-type based on a genetic analysis. It has been shown that killer whales of the Far Eastern seas of Russia have a pronounced foraging specialization, which correlates with the haplotype of the mitochondrial DNA control region. Killer whales with the NT1 and GAT haplotypes previously described for mammal-eating T-type killer whales from the northeast Pacific (also called Bigg’s killer whales) have been observed preying on marine mammals but not on fish. Killer whales with the SR haplotype, previously described for fish-eating R-type killer whales from the northeastern Pacific, preyed only on fish. Two new T-type killer whale haplotypes have been discovered; animals with these haplotypes have been observed preying on large baleen whales. The importance of traditions and social learning in the differentiation of ecological niches in cetaceans has been noted. The specialization to hunt certain prey transmitted from mother to calves allows killer whales of different ecotypes to avoid food competition and acquire morphological and behavioral adaptations that facilitate hunting for a particular type of prey.