|  Resident
killer whales are matriarchal; that is, offspring travel with
their mother for their entire lives. This family unit is called
a matriline. Often several matrilines will be seen travelling
together regularly forming what is known as a pod. Typically
these matrilines are closely related.
Dr.
John Ford, the Aquarium’s first marine mammal research
scientist, did the first systematic research on killer whale
vocalizations. He showed that each resident pod uses a unique
dialect or set of calls. Some pods share certain calls and
are considered to be members of a common acoustic clan. Pods
from different clans share no calls at all, even though they
may live in the same general area and intermingle freely.
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| DNA
Analysis Gel
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Recent
genetic research performed by Dr. Lance Barrett-Lennard, Marine
Mammal Scientist at the Vancouver Aquarium Marine Science
Centre, has established that residents and transients are
genetically distinct populations that rarely if ever interbreed.
He and others have suggested that these two populations of
killer whales are sub-species on their way to becoming separate
species.
Despite
the fact that residents spend their entire lives in their
birth pods, they mate outside of them. Such opportunities
occur most often in the late summer when groups of resident
pods meet in aggregations known as superpods.
Dr.
Barrett-Lennard’s research has shown that not only do
residents mate outside their pods, they usually mate outside
their acoustic clans. Because vocal similarity and genetic
relatedness are strongly linked, this mating pattern is a
very effective way of preventing inbreeding. This behaviour
may in turn explain why killer whales are able to persist
in such small populations.
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