Resident orcas

Resident orcas are fish-specialists, named so because they tend to have small home ranges around areas of large fish populations. Residents are found on both sides of the North Pacific; the Northern and Southern communities almost exclusively eat salmon, while Residents in Alaska appear to be more generalist in their fish preference, eating multiple fish species including salmon, mackerel, halibut and cod. Research by the Far East Russia Orca Project (FEROP) has shown that fish-eating orcas off the coasts of Russia and Japan prefer salmon and mackerel. Resident orcas live in family groups within larger communities, divided by matrilines and pods, and offspring live with their mother for their entire lives. These communities are genetically and acoustically distinct from each other, and each has unique traits specific to their group, like the beach-rubbing behaviour of the Northern Residents.

Bigg's orcas

Another North Pacific ecotype is Bigg’s, or transient, orcas. These are mammal-eating orcas, and like Residents, different communities of Bigg’s orcas specialize on different prey – from harbour seals to minke whales to gray whale calves. They live in small groups and travel frequently over large home ranges, from Southern California up to the Arctic Circle. Also very family-oriented, Bigg’s orcas live in smaller groups but form close associations with their relatives, and some offspring stay with their mother for life. Transient orcas have been recorded by FEROP in the Western North Pacific, and populations on both sides of the Pacific carry high loads of contaminants. As top predators, these mammal-eating orcas accumulate pollutants that are transferred through the food web and end up stored in the blubber of these whales.

Offshore

The third ecotype found in the North Pacific, little is known about the elusive Offshore orcas, as they live far from land – mainly over the outer continental shelf - and are rarely encountered. Their large range stretches from Southern California to the Bering Sea, and their social structure and prey preferences are still unknown. They are usually seen in large groups with more than 50 individuals, and have been seen preying on both fish and sharks. The teeth of Offshore orcas are often worn down, indicating that they’re eating things with rough skin (like sharks). They are the smallest of the three North Pacific ecotypes, and are more closely related to Residents than to Bigg’s orcas, though all three ecotypes are genetically distinct.