Observed foraging behaviour of killer whales (Orcinus orca) in the northwest Atlantic

Killer whales (Orcinus orca) in the northwest Atlantic have been observed feeding on a variety of prey types with >35 cases of confirmed consumption and >55 other interactions since 1866. They have been documented harassing, attacking, and eating minke (Balaenoptera acutorostrata) and humpback whales (Megaptera novaeangliae), dolphins, porpoises, seals, tuna, birds, and other prey. However, it remains unknown whether killer whales are prey specialists in this region. It is likely that distribution, movement, and residency patterns of killer whales are linked to those of their prey. Some killer whales appear to remain year-round in Newfoundland and Labrador (NL) and have been sighted during the spring within pack ice, potentially feeding on breeding seals. Killer whales in southern areas, such as the Gulf of Maine, are sighted less frequently and have historically been in association with Bluefin Tuna (Thunnus thynnus). A majority of successful and confirmed attacks involve minke whales in NL during the summer months, suggesting that minke whales may be one of the most important prey for killer whales in this region. Killer whales are apex predators and so detailing their foraging behaviour in the northwest Atlantic is critical for assessing their influence in this marine ecosystem.