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Orca or Killer Whale
Killer whales pose little or no threat to humans.
Among the best studied populations have been the
pods that range along the west coast of North America, from Washington state to
British Columbia, as well as additional groups in the northern Gulf of Alaska.
Killer whales form stable, long term social groups, and give evidence of
elaborate communication capabilities. They generally travel in groups with fewer
than 20 individuals. Occasionally, larger herds of 100 or more whales may result
from the temporary association of several pods.
Like all odontocetes (toothed whales), killer whales have teeth, one blowhole
opening, and are capable of echolocation. Killer whales typically belong to one
of two types of social groups. Extended family groups that live relatively
near-shore and move somewhat seasonally over well-defined ranges of 60 miles or
so are known as "resident" pods. Less well understood groups of solitary or
small pods of whales which appear periodically over hundreds of miles, and
travel further offshore are referred to as "transient" whales.
Adult male and female killer whales are markedly different in size, with males
growing to 30 feet, and females rarely attaining lengths greater than 22 feet.
One of the most distinguishing characteristics of adult males and females is the
length of the dorsal fin. Male killer whale dorsal fins can reach nearly 7 feet
in height, while female dorsal fins are less than three feet high.
Killer whales can live fifty years or more, reaching maturity in their early
teenage years. The groups, or pods, which killer whales form are based on
complex social patterns which are not well understood. Females appear to provide
continuity to the groups across years, and mature females are frequently
observed with mothers with calves, perhaps providing assistance in calf rearing.
The social groups seem to be based on a dominant male in the company of a small
number of females with whom he mates. These associations last over many years.
At one time, killer whales were taken in large numbers to be kept captive for
public display. Concerns about the effect on pod stability resulting from
removing animals has led to a tendency to protect these groups from capture.
Although killer whales are found in many parts of the world, the full extent of
their behavior and life history remains to be learned. What does seem to be true
is that, although killer whales are intelligent, socially complex, and competent
predators, they pose little or no threat to humans, and are an important part of
the marine ecosystem.
WHAT IS ECHOLOCATION?
Certain marine mammal species have the ability to produce very high frequency
sounds, which can be transmitted over long distances. The sound strikes objects
in the water, such as fish, land formations or ocean flora. The "echo" from the
sound returns to the transmitting animal, and provides information about the
nature of the object. This capability is referred to as "echolocation," since
the animals are able to locate objects in the water on the basis of the
returning echo. Only toothed whales (odontocetes) have been found to possess
echolocating capabilities.
Echolocation sounds are produced in air sacs attached to the respiratory tract,
and are directed through fatty deposits in the forehead (the "melon"). The
sounds are produced in pulses, so that as the echo from each pulse returns, the
animal is able to compare it with the outgoing pulses. The difference between
the two provides the animal with information about the distance to the object,
the size of the object, its shape, and even the material from which it is made.
To the human ear, the echolocation pulses sound like a series of rapid clicks,
because we can only hear a portion of the frequencies which are contained in the
pulsed sounds.
Echolocating abilities are not well understood, but it seems clear that it is a
highly adaptive mechanism for quickly scanning the environment to find out what
may be beyond the limits of visibility beneath the water's surface.
For general information on killer whales, refer to the following:
Center for Whale Research
For scientific information related to killer whales, refer to:
Dalhousie University Killer Whale Research
The Latest news on Killer Whales
For more information, contact us at:
Pacific Whale Foundation
101 North Kihei Road
Kihei, HI 96768
1-800-942-5311
808-879-8860
www.pacificwhale.org
Copyright 1999 Pacific Whale Foundation
May be duplicated only in its entirety for classroom use.
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