WHAT IS AN ORCA?
Residents - Social Structure
Orcas are very social animals. They live in small nuclear and extended families
that we call pods, clans and communities. At the social heart is the orca
mother. She and her children (the maternal group), even her adult sons, stay
together throughout life. If a mother is alive and she has no surviving sons,
she too may be found swimming with her daughter and grandchildren. Adult
daughters who have their own offspring may separate from their mother to
some extent in order to take care of their children's needs, but will usually
be found travelling nearby.
Female orcas may start reproducing as early as 11 years of age, but the average
is closer to 13. Young maturing orca females may become "babysitters" in
preparation for the later responsibility of mothering. Although babysitting
(alloparenting) occurs between other individuals of the maternal group -
e.g. male members or grannies also babysit - it may be a first indicator
that a young female will soon have her own offspring. In her lifetime, a
female may expect to have 4 to 6 offspring and will stop reproducing after
about forty years of age, although there are exceptions to this ( A23 had
a new calf in 1992 when she was estimated at 45 years old ). The gestation
period is about 17 months and we believe that births often occur
in the Fall or Spring.
On average males begin to mature around 12 - 14 years. This period is marked
by rapid growth in the dorsal fin, which up to this point has resembled a
female fin.As the dorsal fin grows it begins to straighten out and lose its
earlier curve. This growth is called "sprouting". Young males of this age
are also often seen in the company of older males. When growth of the dorsal
fin and body stabilize around twenty years of age, this individual is now
considered socially mature and his sexual advances may be taken more seriously
by female orcas.
Beyond the central maternal groups, the pods are extended families of closely
related mothers that are daughters, sisters or cousins, and their children.
A pod can be defined as those orcas that are usually seen travelling together.
For Resident orcas of the Pacific Northwest a pod may number from around
5 to 50 individuals. Pod continuity extends across generations. As individual
lives are long and changes to pod composition are slow, development of new
pods can take a long time, possibly many generations. Because resident orcas
are such social animals, it is not unusual to see large numbers of maternal
groups and pods come together and share the same area.
Orca "clans" are defined in terms of the acoustic traditions of pods within
an orca community. Pods which share common calls belong to the same clan.
Separate clans are composed of pods which do not share calls. In the Northern
Resident Community, there are 3 clans: A, G and R. There is just one clan
in the Southern Resident Community. Pods from separate clans commonly socialize
with each other within the community, even though they do not share calls.
In Washington and British Columbia the Resident orca pods form two distinct
Communities: Southern and Northern. These two communities total about 300
individuals (just over 200 in the Northern Resident and over 90 in the Southern
Resident group). The Northern Resident Community has 16 pods, whereas the
Southern Resident group has three main pods. All these pods are comprised
of a collection of different maternal groups. The whole community is a support
system for each individual, everyone is there for each other. Overt violence
or aggressive behaviour between individuals, even among males, has never
been observed. Instead, orca society is marked by co-operation, co-ordination,
communication, trust and acceptance.
GEOGRAPHIC RANGE OF PACIFIC NORTHWEST RESIDENT COMMUNITIES:
These two communities, despite their close geographic proximity, have never
been observed to mix with each other. Nobody understands why this is so.
Roughly, the Southern Residents' summer range is the waters surrounding Puget
Sound, San Juan Islands, Southern Vancouver Island, the Gulf islands and
the Sunshine Coast of B.C. The Northern Residents' summer range is from Campbell
River on the east coast, and just north of Tofino on the west coast of Vancouver
Island, to just north of the Alaska- B.C. border (north of Prince Rupert).
Typically, these groups are seen from May to December within these ranges.
We do not know where they spend their time in winter, though it is not likely
to be far distant. Nor do we know the dynamics of "off-shore" orca populations
which have begun to be documented in this study area. Since the early 1990s,
more than 200 of these orcas have been identified, but their social organization,
geographic range, and other specifics are largely unknown.