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ORCA--KILLER WHALE
Orcinus orca
meaning of Latin name: a kind of whale
DESCRIPTION:
Orcas are the largest member of the dolphin family. Their
familiar black and white coloration is actually a strategy
of camouflage. From above, their dark back blends in with
the darker water below them, while from below, their whiter
bellies blend in with the sunlit water above. Male orcas reach
30 feet (9.5 m) in length, weigh over eight tons, and have
a dorsal (back) fin up to six feet (1.8 m) tall. Females grow
to 22 feet (7 m), weigh about four tons, and have a three-foot
dorsal fin. Orcas have 50 teeth, which are conical-shaped
and three inches long.
RANGE/HABITAT:
Orcas are found in all the oceans of the world and favor coastal
temperate or cool waters. However, they also range into polar
ice areas. Some orca populations remain local and travel along
predictable routes. Others are transient and move over great
distances.
BEHAVIOR: Orcas are very social. Most pods, or groups,
consist of 5-50 individuals. Studies have shown that each
pod has its own distinctive dialect or accent, and through
this dialect, members of the same pod can recognize each other.
Three distinctive sub-groups of orcas have been described,
residents, transients, and offshores. Residents live in pods
of between 5-50 individuals consisting of two or three older
females and their descendants (children, grandchildren, etc.),
living together throughout their lives. This is called a matriarchal
society. Residents move in more predictable areas than transients,
primarily eat fish, and tend to be more vocal. Transients
live in smaller pods consisting of one to seven individuals,
travel longer and in unpredictable patterns, and primarily
eat marine mammals. Transient will eat any marine mammal including
whales, dolphins, propoises, sea otters, and pinnipeds as
well as sharks and sea birds. By hunting in groups, transient
orcas are able to hunt animals much larger than themselves
and have been known to kill blue whales. Transients are also
distinct from residents because their dorsal fins are more
pointed and they are less vocal. Offshores, as the name suggests,
are pelagic and as a result are rarely observed. They are
known to live in large pods of over 70 and feed primarily
on fish and squid.
Orcas do not migrate in the same sense as baleen whales, but
have seasonal movements, which are tied into prey movement
and environmental changes.
People often wonder why orcas are also called killer whales.
Mariners and whalers observed transient orcas eating other
whales. Thus they were named "whale killer." The
name has since been reversed to "killer whale."
There are no confirmed records of orcas ever killing a person
in the wild.
Capture of orcas for display has become controversial and
more restricted. Warner Brothers' hit film "Free Willy"
prompted people from around the world to demand that Keiko
(the film's star) be moved to a better home and eventually
returned to the wild. Never before has a captive orca been
returned to the ocean. Keiko has many obstacles to overcome
before he can survive in the wild. However, people remain
optimistic about his future.
MATING AND BREEDING: Mating and birth take place mainly
in autumn and winter. During breeding season, pods exchange
members. Gestation (pregnancy) lasts 16-17 months. At birth,
orcas are about six to seven feet long and weigh almost 400
pounds (180 kg). When they are born, their "white"
patches are creamy white to yellow, changing to white at about
one year of age. They nurse for two years.
STATUS: Orcas are not endangered, with at least 180,000
individuals in the antarctic waters alone. However,a resident
orca population in the Pacific Northwest has suffered a 20%
decline in population over a five-year period, prompting the
Canadian government to list them as threatened. Concerned
scientists and conservation groups are also asking the United
States government to list this population on the Endangered
Species List.
One reason for the decline may be starvation, due to a decrease
in their favored prey (salmon). It is also possible that whale
watching boats interfere with their hunting. Another possible
cause may be the effect of pollution such as polychlorinated
biphenyls (PCBs). These chemicals were once used in many industrial
processes but were banned in the United States in the 1970s
when they were found to be dangerous. Despite the ban on their
use in the United States, they are still used in other countries,
and there are still high levels of the chemicals found in
the environment. They get filtered up by bottom-dwelling organisms,
which are then eaten by fish, which are then eaten by other
animals, such as orcas. The chemicals concentrate themselves
in the blubber of these mammals and weaken their immune and
reproductive systems. As resident orcas eat more bottom-dwelling
fish instead of salmon, they accumulate more PCBs. Recently,
transient orcas have been classified as the "most polluted"
animal on earth with PCB levels nearly 500 times that found
in humans. The United Nations is discussing a worldwide ban
of these persistent pollutants.
May be reprinted for scientific and educational purposes
Revised 2/02
Learn more about the following:
Humpback
Whale
Blue Whale
Gray Whale
Beluga Whale
Dolphins
and Porpoises
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Orca/Killer
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