Killer Whales
The scientific order of all types of whales is
Cetacea. This large order is
broken down into three further groups as well:
the toothed whales or Odontoceti,
which includes killer whales, dolphins,
porpoises, beluga whales, and sperm
whales, the baleen whales or Mysticeti,
which include blue whales, humpback
whales, gray whales, and right whales,
and the Archaeoceti order, which are all
now extinct. The genus of these
species is Orcinus orca. Family. The killer
whale is the largest in its
family of delphinid. Bottlenose dolphins, common
dolphins, and Pacific
white-sided dolphins are included in this group as well.
The scientific
name for this family is Delphinidae. Fossil Record. Modern forms
of both
odontocetes and mysticetes can be seen in the fossil record of five to
seven
million years ago. Scientists believe that early whales arose
about
fifty-five to sixty-five million years ago from, now extinct, ancient
land
mammals that happened to venture back into the sea. Habitat And
Distribution:
Distribution. Killer whales can be found in all oceans of
the world. They are
the most numerous in the Arctic Ocean and the Antarctic.
However, their
distribution is limited by seasonal pack ice. Habitat. The
main living
environment for killer whales is open oceans but they can also be
found in
coastal waters as well. Migration. Killer whales are very important
in the
oceans because they cause much of the migration of many fish and other
prey. The
movements of the killer whale to and from certain areas cause the
other prey to
move as well. Population. The worldwide population of killer
whales is unknown,
however they are not endangered whatsoever. Specific
populations in a few areas
have been estimated in recent years and some areas
of the Antarctic alone have
about 180,000 killer whales. The population can
be distinguished because killer
whales travel in pods, or groups. The
resident pods can vary from as few as five
to as many as fifty whales. The
transient pod size varies from one and seven
individuals. Physical
Characteristics: Size. Male killer whales average about
twenty-two to
twenty-seven feet and usually weigh between 8,000 and 12,000
pounds. The
largest male ever recorded was thirty-two feet and weighed about
21,000
pounds. As a male approaches adulthood, it acquires the typical
male
characteristics: it gains weight, and its pectoral flippers, dorsal fin,
and
flukes grow larger than those of females. Female killer whales average
about
seventeen to twenty-four feet and usually weigh between 3,000 and 8,000
pounds.
The largest female recorded was twenty-eight feet and weight
about 15,000
pounds. Body Shape. The killer whale has a sleek, streamlined
body. Its physical
characteristics are adapted for life in an aquatic
environment. Coloration.
Killer whales are easily recognized by their
distinct coloration. The dorsal
surface and pectoral flippers are black,
except for the area below and behind
the dorsal fin. The ventral surface,
lower jaw, and undersides of the tail
flukes are mostly white and the
undersides of the tail fluke are lined with
black. A white "eyespot" is
located just above and slightly behind
each eye and a gray saddle is located
behind the dorsal fin. The distinctive
coloration of killer whales is a type
of disruptive coloration, a camouflage in
which the color pattern of an
animal contradicts the animal's body shape. By the
flickering, filtered
sunlight of the sea, other animals may not recognize a
killer whale as a
potential predator. Thus, making it easy for the killer whale
to get to its
prey. Body Parts. A killer whale has distinct pectoral flippers,
or
forelimbs. They have the major skeletal elements of the forelimb's of
land
mammals, but they are foreshortened and modified. They are rounded
and
paddle-like and are used mainly to steer and, with the help of the
flukes, to
stop. The flukes are the lobe of the tail on a killer whale. They
are flattened
pads of tough, dense, fibrous connective tissue, completely
without bone. A
large male killer whale may have tail flukes measuring up to
nine feet from tip
to tip. All traces of hind limbs have disappeared except
for two reduced, rod-
shaped pelvic bones, which are buried deep in the body
muscle. These reduced
hind limbs are not connected to the vertebral column
however. The dorsal fin,
like the flukes, is made of dense, fibrous
connective tissue with no bones. It
acts as a keel, stabilizing a killer
whale as it swims. The arteries in this fin
help to maintain body
temperature. In males, the dorsal fin is tall and
triangular and in females
it may by slightly curved back. It both males and
females, the dorsal fin may
lean to the right or left, being classified as
irregularly shaped. A killer
whale has a distinct snout-like projection. The
teeth are conical and
interlocking and are designed for grasping and tearing,
rather than chewing.
An individual may have between ten and fourteen teeth on
each side of the
jaw. (About 40 to 58 teeth total.) They are about three inches
long and one
inch in diameter. The eyes of a killer whale are similar to the
eyes of a
cow: big, on each side of the head, and just behind and above the
mouth. The
ears are located just behind the eyes and are small with
inconspicious
openings, with no external ear flaps. A single blowhole is located
on the
dorsal surface of the head and is covered by a muscular flap. This
flap
provides a water-tight seal. This is the only way a killer whale can
breath,
through the blowhole. It is usually in a closed, relax position and
can be
opened when the killer whale contracts the muscular flap. Senses:
Hearing.
Killer whales have developed acute senses of hearing over the
years. They have
responded to tones within the frequency range of about 0.5
to 100 kHz. (The
average range for humans is about 0.02 to 17 kHz.) Most
sound reception, or
hearing, probably takes places through the lower jaw. A
killer whale may also
receive sound through soft tissue and bone surrounding
the ear. Eyesight. Killer
whales also have acute eyesight both in and out of
the water. Glands at the
inner corners of the eye sockets secrete and oily,
jellylike mucus that
lubricates the eyes, washes away foreign particles, and
helps streamline the
eyes as the whale swims. This tearlike film also
protects the eyes from
infective organisms. Touch. Features of the brain
indicate that a killer whales
sense of touch is well-developed. Their skin is
also sensitive to the touch as
scientists have discovered. Taste. There is
very little information about the
sense of taste in a killer whale. It has
been found that they do have taste
buds, but they haven't been well studied.
Smell. Olfactory lobes of the brain
and olfactory nerves are absent in all
toothed whales which indicates that they
have no sense of smell at all. They
rely fully on hearing and their eyesight to
seek prey. Adaptations For The
Environment: Swimming. Swimming speed and
duration are closely tied:
high-speed swimming may last only seconds while
low-speed swimming may last
indefinitely. Killer whales are among the fastest
swimming marine mammals and
can swim speeds of up to 30 mph, but they usually
cruise at much slower
speeds, between two and six mph. Diving. Killer whales
generally dive to
depths of about 100 to 200 feet. The deepest dive under
experimental
conditions is to about 900 feet. When diving, killer whales usually
surface
about every four to five minutes. At the surface they take two to
five
breaths at five to ten second intervals before another dive.
Respiration. A
killer whale breaths through a single blowhole on the dorsal
surface of its
head. The whale holds its breath while below water and at the
surface contracts
its blowhole to breath. Behavior: Social Structure. Killer
whales live in groups
called pods. They are long-term social units that
usually consists of males,
females, and calves of varying ages. Several
smaller pods may join occasionally
to form larger groups of 50 or more
individuals called hers or aggregations.
There is only an occasional
exchange of members between pods, especially during
breeding season. Social
Behavior. Living in a pod creates a strong social bond
between the
individuals. Behavioral studies show that certain animals like
associating
with one another than they do with others. Individual Behavior.
Killer
whale behavior includes spyhopping, hanging vertically in the water with
its
head partially above water, breaching, jumping clear of the water and
landing
on the back or side, lobtailing, slapping the tail flukes on the surface
of
the water, and pec-slapping, slapping a pectoral flipper on the surface
of
the water. Diet And Eating Habits: Food Preferences And Resources. Killer
whales
are the top predators in the ocean and are the most active predators
as well. In
all regions, their diet differs but in the Antarctic, killer
whales eat about
67% fishes, 27% marine mammals, and 6% squids. And in
the Bering Sea, near
Alaska, they eat about 65% fishes, 20% squids, and
15% marine mammals. They also
eat other marine mammals and seabirds. Killer
whales prey on both mysticete and
Odontocete whales, seals, sea lions,
walruses, and occasionally sea otters and
penguins. Food intake. Adult killer
whales eat approximately 3% to 4% of their
body weight in food per day and
fully weaned calves can eat up to 10% of their
body weight per day. Methods
Of Collecting Food. Killer whales often hunt in
pods for their food. They
work together to encircle and herd prey into small
areas before attacking.
They may slide out onto sand bars or ice floes to pursue
their prey, as well.
They surface under ice floes to know prey into the water,
too. Reproduction:
Sexual Maturity. Studies of killer whales in marine
zoological parks suggest
that females become sexually mature when they reach
about fifteen to sixteen
feet, at about six to ten years. Males become sexually
mature when they reach
about eighteen to twenty feet, at about ten to thirteen
years. Mating
Activity. Females become estrus several times during the year.
Breeding
may occur in any season, but is most common in the summertime. In
the
North Atlantic, mating seems to peak in October and November, but in
the western
North Pacific, mating seems to peak between May and July.
Communication: Why Is
It Important? Killer whales probably rely on sound
production and reception to
navigate, communicate, and hunt in dark or murky
waters. Under these conditions,
sight is of little use and communication
becomes much more important. Sound
Production. Killer whales produce
clicks and sounds that resemble moans, trills,
grunts, squeak, and creaking
doors. They also produce whistles. They make these
sounds at any time and at
all depths. The sounds vary in volume, wavelength,
frequency, and pattern.
Each individual sound that a killer whale makes is
termed a call. Calls that
sound the same way time after time are stereotyped
calls. All the stereotyped
calls in a killer whale's repertoire make up a
vocalization system called a
dialect. Pods that associate with one another share
certain
calls.
Bibliography
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Books, 1972
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Whales;
New York: Alan R. Liss, Inc. 1986 Martin, Dr. Anthony R.; The
Illustrated
Encyclopedia of Whales and Dolphins; New York: Portland House,
1990
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