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.
Only females leave the maternal group to form their own maternal groups, although they probably stay in the same subpod with their mother and other sisters or cousins. When the subpod reaches a certain size, it may form a new pod around the dominant female. Another way to investigate the relationships among orca pods in a community is to listen to them. Orca dialects were discovered by John Ford in the late 1970s. Working off Vancouver Island, Ford discovered that no two orca pods sound exactly alike.