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Walrus

Gives birth every 2 years


Order: Carnivora

Family: Odobenidae

Genus & Species: Odobenus rosmarus

APPEARANCE

The walrus, with the wizened and slightly comical face of an elderly man with two long, protruding tusks, is easily the most recognizable of all the pinnipeds. There are two subspecies of walrus, the Pacific and Atlantic walruses, and they differ slightly in size and appearance. The Pacific walrus is the larger of the two. The bulls (males) average at 11-11 ft (3.3-3.45 m) in length and weigh 2000 lbs (889 kg). When carrying maximum blubber, however, the bulls can attain lengths of 13 3/4 ft (4.12 m) and weigh 3700 lbs (1644 kg). The cows (females) are smaller than the bulls, averaging at 9 ft (2.7 m) in length and weighing 1750 lbs (777 kg).

The Atlantic walrus, on the other hand, is slightly smaller. The bulls average at 10 ft (3 m) in length and weigh 1650 lbs (733 kg). When carrying maximum blubber, the bulls can attain lengths of 12 ft (3.6 m) and can weigh up to 2800 lbs (1244 kg). Again, the cows are smaller, averaging at 8 ft (2.4 m) in length and weighing 1250 lbs (555 kg). Both subspecies reach a maximum height of 5 ft (1.5 m).

Walruses are heavily built, with the body fat often accounting for 1/3 of the total weight. The main feature of the head is the squarish snout, which is covered with 400-700 whiskers arranged in 13-15 rows. The eyes are small and the ears are internal. Protruding from the top jaw of the mouth is the walrus's most distinguishing feature: the tusks. The tusks are elongated upper canines and are present in both sexes, although the males' tusks are longer than the females'. The Pacific walrus has longer tusks than the Atlantic. The tusks average at 3 ft (90 cm) for the bulls and 2 ft (60 cm) for the cows. They serve a wide variety of functions, from killing prey to helping them push their massive bulk onto an ice floe.

The short, thick neck of the walrus ends with the massive body. The body is cushioned by up to 6 inches (15 cm) of fat and is protected by a tough, wrinkled skin. The skin is generally pink or red in colour, and gets lighter with age. The colour is caused by the blood vessels beneath the skin when the walrus enters cold water, the skin becomes a pale colour due to a restriction of the blood flow. The face and body are further covered in short hairs that are reddish-brown or pink on bulls and brown on cows.

The body tapers off into four flippers which allow the walrus to swim. The flippers are smooth and hairless on the top side the bottom side is covered with bumps that grip to the ice. The foreflippers are stronger than the hindeflippers and are roughly 1/4 the length of the body; the hindeflippers are 6 inches shorter than the foreflippers.

Walruses have special air sacs below their throats that allow them to bob vertically in the water while sleeping. They are excellent swimmers, but do just as well on land, being able to walk on all fours as fast as a running man.

Walruses communicate with knocks, bells, whistles, and clacks. They have a life span of 40 years.

HABITAT

The Pacific walrus can be found off Alaska and the Chukchi Sea in Russia. The Alaskan herd migrates south in the autumn to the Bering Sea and Bristol Bay, and moves northward in the spring. The Atlantic walrus can be found in small pockets from northern Canada to Greenland, migrating south in the winter to avoid the encroaching ice.

Walruses spend their days in the waters near the shore or resting on ice floes. If no ice floes are readily available or stable enough to support their weight, they may lie on the shore in family groups of 100 or more.

Walruses are avid swimmers and can dive to depths of 250 ft (75 m) for up to 10 minutes.

FOOD

The two subspecies, although found in two different oceans, eat basically the same foods, including clams, muscles, cockles, crabs, shrimp, segmented worms, sea cucumbers, fish, and octopi. Bulls occasionally attack and kill bearded and ringed seals with their tusks, devouring their flesh. They have also been known to feed on whale carcasses.

Walruses find their prey by rooting around in the ocean floor and feeling with their whiskers. When they come across prey, such as a clam, they dislodge it from the bottom by squirting powerful jets of water at it. They then suck up the soft foot of the clam and leave the shell. They may from time to time swallow gizzard stones to help them digest food.

Walruses typically hunt in shallower water 180 ft (54 m) or less and can consume up to 4000 clams in one feeding.

ENEMIES

The walrus has only three enemies: polar bears, killer whales, and man. For hundreds of years, the Eskimos of northern Canada hunted walruses for food, clothing, toys, baby pacifiers, etc, not letting a single piece of the walrus go to waste. Because of this "waste not, want not" attitude, and because they caught walruses with fishing lines, the walrus population was not greatly threatened. With the advent of the gun, however, Eskimos and walrus hunters were able to kill far greater numbers and make quite a profit on them, selling the ivory tusks on the black market. The thick neck was even sought after to make buffering cloths. These hunters almost brought about the walruses extinction. Today, the walrus is an endangered species, with 250 000 Pacific walruses and even fewer Atlantic walruses left today. They could become extinct at any moment, due to their slow breeding habits and the continued hunting of them by the Eskimos.

BREEDING

Female walruses reach sexual maturity at 6-7 years of age; males reach sexual maturity at 7 years of age but do not mate until fully developed at 15 years. Competition between bulls for a cow is usually severe, with tusk fights breaking out. The winner of such fights will then proceed to mate with several females. The breeding season is from January - March, and the gestation period lasts for 15 months. 3-4 of those months are spent with the blastula in suspended development before finally implanting itself in the placenta. When the calf is finally born the next April, May, or June, the breeding season has already passed. Therefore, the female only births one calf every two years.

The calf is 50 inches (125 cm) long at birth. At two weeks of age it can swim, at 6 months it can eat solid food, and at two years it leaves its mother and joins a herd of young walruses.

RELATIVES

There are no other members in this family. The Pacific walrus is O. r. divergens, and the Atlantic walrus is O. r. rosmarus. A third population of walruses found in Russia is thought to be an intermediate between these two subspecies.

RESOURCES CITED

1. Funk & Wagnall's Wildlife Encyclopedia "Walrus" vol 21 pg 2492-2496. BPC Pub Ltd, NY, 1974
2. "Walrus" Wildlife Fact File. IM Pub Inc. USA
3. www.mnh.si.edu/arctic.html/walrus.html
4. www.pbs.org/kratts/world/oceans/walrus/
5. www.seaworld.org/animal_bytes/walrusab.html
6. tqjunior.advanced.org/3500/walrus.html
7. www.r7.fws.gov/mmm/walrus/biology.html

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