Killer Whale
Orcinus orca
Killer Whale
Behaviour
Killer Whale
Biology
Killer Whale Breeding
Behaviour
There is no
evidence that northern and southern residents interbreed even
though their ranges overlap and they share many ecological and
behavioural similarities (Baird & Stacey 1988, Stevens et al.
1989, Hoelzel and Dover 1991, Ford et al. 1998). Killer whale
males
and females are sexually mature when they are about 15 years
old. Gestation period is 15-17 months. Females breed about
every 5 years. Calving can occur at any time but mostly over
the winter. There is not a great deal of data on calf
mortality but the records suggest that about half of calves
die in their first six months of life. Average life expectancy
is about 29 years for females and 17 years for males (Olesiuk
et al. 1990).
Killer Whale
Social Organization
Clans are
thought to exist among resident type killer whales in southern
Alaska (Yurk et al. 2002). Killer whales live in stable
matrilines that associate half the time with other whales in
pods. Yurk et al. (2002) believe that pods are closely related
because they share a unique repertoire of discrete calls.
Seven discrete call types have been recorded from killer
whales in southern Alaska. They believe that the similar
acoustics of these whales reflects a common ancestry within
groups, which they presume are cultural and hence meet the
definition of clans.
Transient killer whales off southern Vancouver Island
exhibited strong, long-term associations between individuals
(Baird and Whitehead 2001). These ‘pods’ consist of various
ages of both sexes but typically contain an adult female and
one or two offspring. The mother and offspring maintain a bond
into adulthood. Some males disperse from the pod to spend some
of their time alone but occasionally joining groups that
contain potentially reproductive females. Females that
disperse from the pod appear to be gregarious but remain
socially mobile. Resident killer whales do not disperse from
their groups (Baird and Whitehead 2001).
Genetic comparisons between resident and transient whales show
highly significant differentiation at both nuclear and
mitochondrial loci that suggest not much genetic dispersal
between the two groups of whales (Hoelzel et al. 1998).
Killer Whale
Feeding behaviour
It is well established that transient
killer whales eat mostly on marine mammals whereas residents
and probably offshore killer whales eat mostly fish (Morton
1990, Jones 2005). Off
the north end of Vancouver Island, whales enter Johnstone
Strait for the period of July to October coinciding with the
time of salmon migration (Nichols and Shackleton 1996). Whales
coincide with areas used by sockeye and chinook salmon runs.
Twenty-two species of fish and one species of squid have been
found in the diet of resident killer whales with a clear
preference for salmon, especially chinook (Ford et al. 1998).
Transient killer whales preyed only on pinnipeds, cetaceans,
and seabirds, especially harbour seals (Phoca vitulina).
In Prince William Sound, Alaska, the dietary preference was
the same; the respective diets of resident and transient pods
were nearly exclusively salmon and marine mammals (Scheel et
al. 2001).
Transient killer whales are most efficient in terms of energy
intake when they forage in groups of three individuals (Baird
and Whitehead 2001). They travel quietly, rarely vocalizing,
and spending little time on the surface. They approach areas
where seals gather underwater and snatch their prey unawares.
They chase down and crashland on porpoises or kill them
underwater. Transients will also take large whales by tearing
at the flukes, flippers, and lips and attempting to drown
calves by holding them underwater. Seabirds and seaducks are
snatched them from the surface and probably caught underwater.
Resident killer whales eat fish by catching them during
underwater chases.
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