Recent research has raised the possibility that Bigg's killer whales in the North Pacific may have attacked and preyed upon a different ecological group known as resident killer whales. The study, conducted by a team led by Professor Olga Filatova from South Denmark University, indicates that distinctive tooth marks found on the remains of resident killer whales suggest they could have been preyed upon by Bigg's killer whales, who share the same habitat. This discovery points to the hypothesis that resident killer whales may have developed their unusual social structure—characterized by large, matriarchal family units—as a strategy for avoiding predation.

The research highlights the classification of orcas globally, which is divided into three main ecological forms: the resident killer whales, notably found in the coastal waters of the North Pacific and known for their large family groups; the more fluid Bigg's killer whales; and other orca populations inhabiting various regions such as the North Pacific, North Atlantic, and Antarctica. Despite being classified as a single species, significant differences in diet, social structures, and communication styles among these populations have led to discussions about potential subspecies classifications. Notably, while resident killer whales primarily feed on fish and avoid attacking dolphins, Bigg's killer whales are more aggressive and hunt a wider array of marine mammals, supporting their reputation as apex predators.

The findings from this research, published in the journal Marine Mammal Science, underscore the complexity of orca behavior and social organization. The DNA testing of the two identified specimens from the Russian Bering Islands confirmed their identity as resident killer whales. Professor Filatova emphasizes the uniqueness of the matriarchal social structure of resident killer whales, which may not have many parallels in the animal kingdom, further illustrating the intricate dynamics within this species and their ecological interactions.