BIOLOGIYA MORYA, 2023, Vol. 49, No. 6, pp. 417-428

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

© 2023 O. A. Filatova^{1, 2}, I. D. Fedutin^{1, 2}, O. A. Belonovich³¹, E. V. Volkova⁴, T. V. Ivkovich⁵, M. E. Ismail^{1, 6}, I. G. Meschersky⁷, O. V. Titova⁷, S. V. Fomin⁸, O. V. Shpak⁹

¹Biological Faculty of the Lomonosov Moscow State University, Moscow 119234, Russia;
²Department of Biology, University of Southern Denmark, 5230, Odense, Denmark;
³FSBI "National Park Commander Islands named after S.V. Marakov", Kamchatka Territory, Nikolskoye community 684500, Russia;
⁴FSBI "Kronotsky State Natural Biosphere Reserve", Kamchatka Territory, Yelizovo 684000, Russia;
⁵KIT School, St. Petersburg 191123, Russia;
⁶Faculty of Science, Port-Said University, 42526, Egypt;
⁷A.N. Severtsov Institute of Ecology and Evolution RAS, Moscow 119071, Russia;
⁸Kamchatka Branch of Pacific Geographical Institute FEB RAS, Petropavlovsk-Kamchatsky 683000, Russia;
⁹Independent researcher, Kharkiv, Ukraine

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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 nutritional specialization, which correlates with the haplotype of the mitochondrial DNA control region. Killer whales with the NT1 and GAT haplotypes previously described for carnivorous 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 piscivorous 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.

Key words: cetaceans, killer whale, Orcinus orca, nutrition, ecology, ecological niche, ecological diversification, ecotypes.