Social Organization & Mating
Whales make their home wherever they happen to be in their aquatic enviornment, unlike most terrestrial mammals which have dens or nests and preferred feeding areas. For killer whales, home is family. Resident killer whale pods are MATRIARCHAL, meaning that sons and daughters stay with their mother throughout their lives, even after they have offspring of their own. The bonds between siblings usually remain strong even after the mother has died. A matriarch and all of her descendents are referred to as a MATRILINE. A POD is a larger unit that is made up of one or more matrilines that travel together at least half the time and that probably stem from a deceased matriarch. A CLAN is a group of pods that share similar calls or dialects.
The social system of Biggs (transient) killer whales is more fluid than that of residents. Although many Biggs (transients) stay with their mothers for life, some leave their mother's group and join up with other Biggs (transients). Because they are so different from residents in this respect, most researchers don’t refer to transient social groups as “pods”.
Determining Mating Patterns with Genetics
How do resident killer whales avoid inbreeding if sons and daughters stay with their mother all their life? Dr. Lance Barrett-Lennard, senior marine mammal scientist at the Vancouver Aquarium Marine Science Centre, recently completed a long-term study that helped to answer this and other questions that have long eluded killer whale researchers. By analyzing DNA from tiny skin samples taken from more than 300 killer whales in B.C. and Alaska, Lance could determine two things: paternities (who the fathers are) and how communities of killer whales are related to one another. His study showed that resident killer whales not only avoid mating with pod-mates, but that they have a complex mating system that prevents breeding between other close relatives and closely resembles traditional marriage systems in some indigenous human populations.
- Paternity tests showed that mating never occurs within matrilines, rarely if ever occurs within pods and usually occurs between the members of different clans. Clan-based marriage systems were also the rule for coastal First Nations peoples in British Columbia, and also existed in Australian aboriginal groups and in various indigenous societies in China and Africa.
- There is a clear link between the calls that killer whales make and who they mate with. Killer whales tend to mate with partners that don't sound like themselves. This makes sense, because Lance also showed that the more similar the dialects of two groups, the more related they are.
- Biggs (transient) and resident killer whales represent distinct lineages with little or no exchange of individuals or interbreeding. The differences are so great that they have likely been isolated genetically for many thousands of years.
- Northern and southern resident killer whales are more closely related but haven't interbred for hundreds of generations.
Photo: John Ford
Genealogy Studies of killer whales along the coasts of Washington and British Columbia have been taking place for approximately 40 years. Due to the long duration of these studies every resident killer whale along the British Columbia and Washington coast has been photographed and identified as belonging to a specific matriline.
Comprises all pods that meet up and intermingle or travel together from time to time; pods from different communities have never been seen to mingle or travel together.
A set of one or more pods that share a related dialect; pods within a clan descended from a common ancestral group and are therefore more closely related to each other than to pods from other clans.
One or more matrilines that usually travel together; term relevant only to resident whales.
The basic social unit of resident killer whales, composed of a mature female and her immediate descendants; descendants may include mature males and mature daughters and their offspring.
DNA analysis gel
Each row is a "microsatellite" DNA from a different individual, except for the mult-bank rows at the edges that contain reference DNA.
Photo: Lance Barrett-Lennard Arrow (B16) traveling with Uncle Slingsby (B10).