The basic unit of killer whale
social structure is the matriline. This means that the
most common and most consistent grouping of killer
whales consists of a mother and her growing offspring.
Killer whales mature slowly and it
is not unusual for young whales to stay with their
mothers for more than a decade. Long after the babies
stop nursing, they presumably benefit by staying with
their mothers because of the protection that she can
provide and because of the need to learn the hunting
lifestyle by observing and gradually acquiring their
mother's skills. Thus, when one encounters a group of
whales in the wild, it is most likely to consist of an
adult female accompanied by two or three of her
offspring -- spaced out over a range of ages.
Among the "Resident" whales in the
North Eastern Pacific, matrilineal cohesion is extreme.
In this ecotype of orca, both male and female offspring
remain with their mothers long into adulthood such that
large pods form that consist of a grandmother, a number
of her adult male and female offspring, and new calves
that are born to her daughters.
It is not yet clear how and when
killer whale males and female court and mate with each
other. But it is suspected that this occurs on occasions
when different family pods cross paths and briefly
intermingle in big gatherings called "super pods".