Orcas are probably the most socially bonded of all mammals on our entire planet. Resident orcas spend their entire lives within their immediate family group. At the centre of the family is the orca mother, who by her endurance and longevity provides continuity and stability to her matriline. Succeeding daughters carry on the family traditions and claim their own matrilines only after her death. Even a mother's adult sons stay with the family throughout their lives. Closely related matrilines form a larger social group called a "pod". The pods which share a common acoustic heritage form a "clan". The clans which share a common geographic range form a "community". Less is understood about the transient population's social structure. Although there seem to be close social groups which have cohesion, there are times when individuals do disperse from the natal group. However, within the transient community on the North American west coast, different groups, from diverse areas, have been known to travel together for a time, thus demonstrating a strong social sense at the community level also.