Fact: Transients eat only marine mammals and birds.
Fact: Transients do not associate with resident (fish eating)
killer whales
The transient killer whales are a genetically separate
community of killer whales that live some of their lives
in British Columbia. We are very lucky in southern BC,
as we get the opportunity to view both types (residents
and transients) on our whale watching excursions from
Victoria - though often not on the same trip! The transient
killer whale community is currently considered a distinct
eco-type of killer whale that specializes on eating
warm-blooded prey. Their diet includes all other marine
mammals (excluding other killer whales) and occasionally
birds.
The name “transient” can be a little confusing,
as it sounds as if they are just passing through British
Columbia, however we now know that this is not the case.
Due to on-going scientific research conducted in British
Columbia, Washington, California and Alaska, we know
that the transients are not “passing through”
as their name implies, but that they have a very large
range, which extends from southern California to the
Aleutian Islands. As of 2000, there were 219 catalogued
transients killer whales (pers. comm. Graeme Ellis),
however the real population number is probably higher
than this.
Although the residents and transients are both killer
whales, they are quite different from each other. The
residents live in their maternal family units and are
often seen interacting in relatively large groups. The
largest groups (>90) occur when the entire community
comes together, in what is called a superpod. Superpods
are seen a few times each summer by Prince of Whales
passengers. It is truly an awesome experience.
Transient killer whales have a much more fluid social
structure, and do not appear to have the life long family
bonds that the residents do. Transient killer whales
are typically seen in groups of three to eight individuals.
However, it is not uncommon to find a single male transient
apparently swimming alone. |
There is much to be learned about the dynamics of transient
killer whale society. The list of what we do not know
is certainly longer than the list of what we do know.
One aspect of their biology that appears to be almost
certain is that transient killer whales do not eat fish.
They appear to have a diet that is made up of warm-blooded
prey including marine mammals, birds and the occasional
terrestrial mammal such as deer or moose.
In southern British Columbia, some of their preferred
meals include harbour seals, Dall's porpoise and harbour
porpoise. When viewing transients from a Prince of Whales
vessel, we do sometimes observe transient hunting behaviours,
which can include circling seal haul out sites or chasing
a porpoise. Though we may see these behaviours, we rarely
see a kill (rarely, but not never).
At Prince of Whales, we recognize and respect that
residents and transients are very different types of
killer whales with different ecological requirements.
To minimize the human impact on these marine mammals,
we employ different operating procedures for observing
these animals in their natural habitats.
OFFSHORE KILLER WHALES
In British Columbia, there is a third eco-type of killer
whale, known as the "offshore" killer whales.
The offshore killer whale community has an overlapping
range with both the residents and transients. They are
believed to range from California to Alaska, mostly
in offshore regions (hence their name), and it appears
that they primarily travel in large numbers, with 250
individuals catalogued as of 2004 (pers. comm., Graeme
Ellis). We do not see this type of killer whale very
often in the inland waters of southern British Columbia;
however, once in a while we are fortunate to catch a
glimpse of them. Offshores are thought to be slightly
smaller fish eating killer whales that do not associate
with either our resident or transient killer whales.
Personal Communications
Graeme Ellis, Fisheries and Oceans Canada, Pacific Biological
Station, Nanaimo, British Columbia, Canada. |
