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A mother resident killer whale is the leader of her family; her children usually stay with her all their lives. When her daughters have children of their own, those kids stay with the group too. A group made up of a mother, her children, her grandchildren, and maybe even her great-grandchildren, is called a matriline. When the oldest mother dies, her daughters begin to travel together less frequently. Eventually, they might form matrilines of their own.
Pods are made up of matrilines that hang out together a lot. Scientists think that sometime in the past, the matrilines all shared a common maternal ancestor. It could be that they used to be one big matriline until the oldest mother died.
Pods that share a similar set of calls, or dialect, make up a clan. Each group of whales makes a different set of sounds, which is likely passed down from mother to children. Therefore, the more related the whales are, the more similar they sound.
This is probably how killer whales can tell who’s family when various pods get together. Even though residents stay with their mothers all the time, they manage to avoid inbreeding. One theory is that they choose mates based on how different they sound.
You can find out more about killer whale dialects in the Sounds All Around section.
Transient killer whales live in much smaller groups than residents, probably because it’s easier to hunt that way. A small group can sneak up on an unsuspecting seal or porpoise more easily than a whole matriline.
Transients sometimes leave their family group to join up with other transient killer whales. Sometimes they stay away from their families for the rest of their lives, but sometimes they go back to their moms after a few years. As a result, it’s harder for us to organize the transients into families.
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