1. Killer whales live in cohesive long-term social units called pods.
2. The size of a pod usually varies from fewer than 5 to about 30 individuals. Pod sizes may change with different geographic locations; off Alaska and Antarctica, groups of more than 100 animals have been seen.
3. Pods usually consist of males, females, and calves of varying ages. Females and juveniles generally remain in the center of the pod, while adult males swim at the wings.
4. A pod is not the smallest or largest social group in a killer whale community. Researchers have identified the most fundamental social units in a resident pod as maternal groups. A maternal group consists of a mother and her offspring (not including adult daughters with offspring of their own). One or more maternal groups may travel together in a subpod. Whales in a subpod are likely to be closely related; a subpod contains mothers and daughters, and probably sisters and cousins.
5. A clan is a social level above the pod level. Clans are made up of pods in an area with similar dialects and are thought to be related. These pods may have developed from one ancestral pod that grew and fragmented over time. Finally, the top level of the killer whale social structure is a community. A community is composed of several pods that have been seen to travel together. Pods from one community have not been observed traveling with those of another, even if their ranges overlap.
6. Sometimes smaller pods may join to form groups of 50 or more individuals (up to 500 in some cases) which are sometimes referred to as herds or aggregations.