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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Whales; New York: Alan R. Liss, Inc. 1986 Martin, Dr. Anthony R.; The
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