Ryazanov, S.D., Fomin, S.V., Atopkin, D.M., Eliseikina M.G.
Oceanology 2026; 66(2): 299-308
Three ecotypes of killer whales are recognized in the northern Pacific Ocean: the R type, the T type, and the offshore type. It is believed that the diet of T-type killer whales, which are currently regarded as a distinct subspecies (or species), is based primarily on marine mammals; however, data on the contents of the gastrointestinal tract (GIT) of these animals remain scarce. A local population of Steller sea lions inhabits the Commander Islands, and its abundance has been declining for reasons that remain unclear. In 2021, a carcass of a T-type killer whale was found on the archipelago, and the first report of predation by a killer whale on a Steller sea lion in the Commander Islands was published. We carried out a detailed analysis of the GIT of this killer whale. The GIT contained hair of a true seal, most likely a bearded seal, but not a Steller sea lion, as well as beaks of large squids belonging to the family Ommastrephidae. The total mass of squids ingested by the killer whale was estimated to reach tens of kilograms. The resulting data refine and complement existing information on the feeding habits of T-type killer whales and demonstrate that, in addition to marine mammals, squids may constitute a substantial component of their diet.
