The northern community ranges from northern Vancouver Island to Alaska, while the southern community lives off southern Vancouver Island and in Puget Sound, Washington. 80 whales in 30 pods. With pointed dorsal fins, they also look slightly different from the other orcas, and they travel in smaller groups of only 2 to 7 individuals per pod, while resident pods have 5 to 50 individuals. Their diet is also distinctive. Transients eat mainly marine mammals, including seals, sea lions and, occasionally, dolphins and whales.
Residents eat fish such as salmon.
The photo-identification method has been the lifework of the late Michael Bigg and his associates, Graeme Ellis, Ian MacAskie, John Ford and Ken Balcomb, although many others have contributed to the study. Thousands of photographs showing two or more orcas close to each other have verified field sightings. Analyzing such associations, some two dozen researchers engaged in the study have determined that the social order of the resident orcas apparently revolves around the female adults. The smallest resident whale unit is a maternal group that is composed of a mother and her offspring. Male offspring stay with their mothers.