Killer Whales (1353 words)

Killer Whales
Killer whales are an important subject of mythology for many indigenous peoples,
especially the Native Americans of the Pacific Northwest. The whales have not
been hunted extensively by humans, although they have been hunted by some shore
whaling operations, and some individuals have been taken as aquarium show
animals from the waters around the Pacific Northwest and Iceland. Killer whales
are perceived by many near-shore fishermen to be in competition with human
fishing activity (Anheiser Busch 1). The killer whale, or Orcinus orca can be
found worldwide in all seas from both tropics to Arctic and Antarctic oceans.


They are one of the most well known whales because of the captivity of Shamu at
Sea World and the other studies that are widely publicized (2). The male killer
whale has an average length of 6.7 to 7.0 meters and can weigh between 4,000 to
5,000 kilograms (Knight 5). The female killer whales are smaller having a length
of 5.5 to 6.5 meters and weighing 2,500 to 3,000 kilograms. They have 10 to 12
pairs of large conical teeth in each jaw (Evans 12). Their coloration is very
striking. They have black on the back and sides and a white belly that extends
as a rear-pointing lobe up the flukes and less markedly near the head, and
around the throat (15). They are also white on the chin and underside of their
flippers with a distinctive, conspicuous white oval patch above and behind each
eye. This coloration varies depending on regional variations. Killer whales can
have indistinct gray saddles over their backs just behind their dorsal fin
(Evans 16). This is called countershading. Countershading enables the whales to
be camouflaged from their prey (Wolfe lecture). They have a stout torpedo-shaped
body with a conical-shaped head. Their flippers are large rounded and
paddle-shaped with a centrally-placed dorsal fin. The dorsal fin is
sickle-shaped in adult females, but very tall and erect in adult males. There
are some variations in morphology between regional populations but vocal
dialects vary more between pods than geographically. There is no exact known
population size. But the largest numbers are in the Antarctic where the
population is estimated at more than 160,000 (Wheelock Colege 1). Killer whales
may be solitary or live in groups of 2 to more than 50 animals. Food items
include squid, fish, skates, rays, sharks, sea turtles, sea birds, seals, sea
lions, walrus, dolphins, porpoises, and large whales such as fin whales,
humpback whales, right whales, minke whales, and gray whales. They are even
known to attack the sperm whale and blue whale. On the Atlantic coast of South
America, as well as on islands of the Indian Ocean, killer whales have been
observed lunging through the surf and coming right onto the beach in pursuit of
elephant seals and sea lions (Holt 17). After such an attack the whales have to
wriggle and slide back into depths adequate for swimming. In captivity, killer
whales eat about 45 kg of food per day but free ranging animals probably require
much more. Although these are obviously proficient and voracious hunters, killer
whales are not known to have ever attacked a human (Evans 123). At sea they are
usually seen in “pods” of 5-20, although up to 150 have been seen
together at one time. Large groups probably consist of several pods which have
temporarily aggregated. Pods themselves appear very stable for many years, with
little emigration or immigration (124). They are highly cooperative and the
group functions as a unit when hunting, making these delphinids extremely
efficient predators. Groups usually contain adults of both sexes but sometimes
females with young will form their own groups (125). Although much research has
focused on killer whale pods around Vancouver Island and on the mainland coast,
very little is known about the whales often found in the Queen Charlotte
Islands, known as “offshore” killer whales. This separate population
of killer whales appears to share similar behaviors and the fish-eating
lifestyle particular to resident whales but appear to maintain an offshore
distribution and are unique in their vocal dialects ? indicating they’re
unrelated to any transient or resident pod. Offshore whales tend to be seen in
large groups of 30 to 60, and are seldom seen in protected coastal waters. At
present, there are limited details concerning the offshore population’s range,
social organization or life history. However, we hope that it will be possible
to fill in many of these gaps in the future, and to determine if and how these
offshore whales might be related to the well-known inshore resident and
transient populations (Wheelock College 15). The reproductive habits of these
whales are poorly known. The males may mate with more than one female and mating
may occur throughout the year, although most calves seem to appear in autumn or
winter in shallow waters. The female gives birth to a single calf 16 or 17
months after mating. The calf is nursed for 14 to 18 months (Anheiser Busch 16).

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Calves are approximately 2.4 m long at birth and reach sexual maturity when
4.9-6.1 m in length. Groups of killer whales seem to be remarkably stable, with
males and females staying in their natal pods, or groups, for life.


Consequently, researchers believe that, to keep inbreeding to a minimum, mating
does not occur between members of the same pod as often as it does between
members of different pods (Holt 12). Like the complex social organizations in
which they live, killer whales also have very distinct and complex methods of
communicating. Vocal variations of resident, transient and offshore killer
whales have identified distinctive dialects that are used to recognize
particular groups of whales and relationships between groups and populations
(Knight 10). Killer whales use echolocation to gather information about their
surroundings. They send out high-frequency clicks that bounce off prey and other
objects and they interpret the returning echoes. Killer whales communicate by
means of rapid-fire click trains that sound like rasps and screams, although
when they are on the prowl for marine mammals, which have acute underwater
hearing, they can be silent for hours at a time. Other sounds such as squeaks,
squawks and screams are sounds used for social contact within and between groups
of whales. These sounds, which are specific to a single group of whales, make up
each group’s dialect (Holt 5). Killer Whales, like all animals, have their own
specific niche, or job in their ecosystem. They are top predators. Their job is
to weed out and hunt the sick or weak animals. This process allows a species to
thrive. If the sick and weak are allowed to live, then reproduce, they pass on
their sickness or weakness to their young, thus making the entire population
weaker. This demonstrates “Nature’s Multiple Choice Question: a)Move b)Adapt
c)Die.” These whales are believed by some scientists to have evolved from land
mammals (Wolfe Lecture). We do not use these whales for any purposes like food
or medicine, although they used to be hunted along with humpback whales and
Pseudo Orcas, or false Killer whales for oil and blubber. We do however, capture
these whales to perform in Marine Theme Parks, and in some, like Sea World, we
use them to educate the public (Killer Whale 8). Killer whales have no natural
enemies, their only enemy is man (Wolfe). I chose this animal because ever since
I was little, I have been fascinated with these whales. I remember my first time
going to Sea World when I was 7 years old. I saw this giant creature doing all
sorts of tricks and I was mesmerized. Back then you didn’t learn about the
whales, you just watched the tricks. Now, over the years, the shows have become
more and more focused on education. I wanted to learn more, which is why I chose
this mammal. Man doesn’t know enough about these whales. They are still
fascinating animal lovers, especially since the making of the movie “Free
Willy”. Millions of people visit parks like Sea World ever year, and learn
more about these beautiful creatures. We must continue to study them in their
natural environment and learn as much as we can.


Bibliography
Anheiser Busch. “Animal Resources.” http://www.SeaWorld.org/infobook.html.


1998. Evans, Peter. Whales ; Dolphins. Facts On File. New York, NY. 1987.


Holt, George. “Orca.” http://thewildones.org/SFC/Seana/george.html. 1998.


Knight, Tim. “Killer Whale Info and Pictures.” http://www.selu.com/~bio/wildlife/
mammal/whale/killerwhale01.html. 1997. Wheelock College, Boston. “WhaleNet.”
http://whale.wheelock.edu/. 1997. Wolfe. Oceanography class Lectures and
Handouts.

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