Resident killer whales are typically encountered in groups of 10 to 25 or more individuals. They feed on fish, are highly vocal, and have regular seasonal patterns of habitat use.

Transient killer whales are silent predators of marine mammals, including seals, seal lions, and other cetaceans. They travel in groups of two to five individuals and their movements tend to be more erratic.

Little is known about the recently discovered offshore population, except that they often travel in groups of 30 to 60 individuals and spend most of their time over the continental shelf.

Resident killer whales are matriarchal; that is, offspring travel with their mother for their entire lives. This family unit is called a matriline. Often several matrilines will be seen travelling together regularly forming what is known as a pod. Typically these matrilines are closely related.

Dr. John Ford, the Aquarium’s first marine mammal research scientist, did the first systematic research on killer whale vocalizations. He showed that each resident pod uses a unique dialect or set of calls. Some pods share certain calls and are considered to be members of a common acoustic clan. Pods from different clans share no calls at all, even though they may live in the same general area and intermingle freely.

Recent genetic research performed by Dr. Lance Barrett-Lennard, Marine Mammal Scientist at the Vancouver Aquarium Marine Science Centre, has established that residents and transients are genetically distinct populations that rarely if ever interbreed. He and others have suggested that these two populations of killer whales are sub-species on their way to becoming separate species.

Despite the fact that residents spend their entire lives in their birth pods, they mate outside of them. Such opportunities occur most often in the late summer when groups of resident pods meet in aggregations known as superpods.

Dr. Barrett-Lennard’s research has shown that not only do residents mate outside their pods, they usually mate outside their acoustic clans. Because vocal similarity and genetic relatedness are strongly linked, this mating pattern is a very effective way of preventing inbreeding. This behaviour may in turn explain why killer whales are able to persist in such small populations.