The social structure of killer whales is very distinct. When focusing on resident killer whales specifically, it is important to note that the basic social unit is called a matriline. This is a group of killer whales which are connected by maternal descent. This core group is highly stable with bonds that are extremely strong. Individuals are rarely seen apart for more than a few hours. Studies conducted have shown that individuals have not been seen to permanently leave any of these observed resident matrilines. Matrilines may consist from 1 to 4 generations of related whales. Pods are the next social structure - which consist of related matrilines that travel and hunt together. Pods are less stable and it is not unusual that a matriline will break away from the pod for an extended period of time. Beyonds pods, are clans. Clans are made up of pods with similar vocal dialects, and may be related. Pods may have developed from one ancestral pod which fragmented over time. Pods from different clans are frequently seen traveling together. The last social level is a community. Whales do not share common maternal links or vocal similarities, but simply share a geographic range.
Similar to resident killer whales, the matriline is basic social unit in transient whales. However they are typically smaller in size, and juvenile and adult offspring can disperse for long periods of time or even permanently. Consistency in grouping patterns is not common. Associations are more dynamic in transient killer whales as well.