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WALRUS
Odobenus rosmarus
(Linnaeus, 1758)

Order Carnivora, Family Odobenidae. Three subspecies are recognized: Atlantic walrus,
Odobenus rosmarus rosmarus; Pacific walrus, Odobenus rosmarus divergens; and
Laptev Sea walrus, Odobenus rosmarus laptevi.

DERIVATION: Odous or odonto means "tooth"; baino (Greek) means "I walk," referring
to the fact that tusks are something used to help the walrus move about.
Rossmaal or rossmaar (Norwegian) is derived from the
Scandinavian word.

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The walrus is a large pinniped; seals and sea lions are also pinnipeds. The walrus lives on the edge of the Arctic ice sheet and is often hunted by polar bears and killer whales (orcas). The predators however may be the ones injured as walruses fight back, and sometimes, they even cause serious injury to their attackers. Its ivory tusks are used for a number of things, including protection when attacked by polar bears, killer whales, or human hunters in kayaks. It is the only living pinniped with external tusks.

They are very slow and clumsy on land, but in the water they are fast and strong. They can dive up to 300 feet to obtain their favorite food from the sea bottom: clams. Their diet also consists of snails, mussels and 40 other kinds of invertebrates. If very hungry, they will eat seals. They are primarily bottom feeders and may dive for up to ten minutes. This practice means that they require access to shallow banks and coastal areas. They feel their way along the bottom with their sensitive whiskers and apparently suck clams from their shells. As many as 3000 to 6000 tiny clam siphons can be ingested in a single feeding session. The idea that tusks are used for digging clams and other food is almost certainly wrong because of the patterns of wear on their tusks and facial bristles. In addition, observation of captive walruses feeding discounts this notion.

Their fore flippers do not have exposed nails which enables the animal to hunker along on land or ice and to clamber onto rocky ledges. Their hind flippers can be rotated forward to allow an ungainly form of walking on land.

Its head is small relative to its bulky torso. Its broadly flattened muzzle has stiff, colorless whiskers (vibrissae) and paired vertical nostrils immediately above its bristles. Its often-bloodshot eyes are set high on the sides of its head.

Walrus skin is very thick and the male's wrinkled, heavily scarred hide is covered by cinnamon brown hair. In adult males, their massive neck and shoulders are covered with wartlike nodules. A female has more hair throughout her life. Males shed most of their hair in June and July; it is replaced in July and August. Shedding in females is less well defined. Molting in walruses is more prolonged than in most other sparsely-haired pinnipeds. Calves have short, gray to gray-brown hair and their flippers become black within two weeks after birth.

Because of air sacs in their throat, they can sleep with their heads held up in the water. These sacs act like a life preserver. A thick layer of fat insulates the walrus in the cold Arctic waters. Their nostrils are closed in the resting state.

They are usually found in herds, especially when onshore. Walruses are very gregarious and often found in groups of many hundreds. During the nonbreeding season, males and males are sometimes segregated, but on certain traditional summer and fall haulout grounds, both sexes and various ages are represented. The compact huddling of walruses when they are hauled out does not automatically mean that their social associations are totally amicable. An individual may compete for a more favorable spot and use their tusks and body size to win or maintain social status. They congregate in harems with the large bulls assembling numerous cows into groups. The bull defends his group against competitors and mates with cows in the group. Aircraft can cause stampedes into the water by all the walruses at a haul out site, which may result in the calves being crushed.

It is believed that copulation occurs underwater and that attachment of the fertilized egg to the uterine wall is delayed for four to five months. Pups are born approximately 15 months after conception. Sexual maturity is attained in Pacific females at around eight years. Males are capable of mating successfully by the age of ten, but they seem socially incapable of competing for mates under natural conditions until they are approximately 15. Birth takes place between mid-April and mid-June but usually in May . Females in their prime give birth in alternate years.

Calves may nurse for as much as two to two and a half years. A nursing mother sometimes assumes an upright posture in the water. A pup may hang upside down, with its rump and hind flippers exposed as it nurses. Walruses nurse on land or ice, but aquatic nursing appears to be more common in walruses than in other pinnipeds. No other pinniped gives such a consistently prolonged period of lactation and maternal care to their pups.

A pup often rides on its mother's back, especially when fleeing from danger. A mother will use her fore flippers to grasp her pup and dive with it when threatened. The solicitude displayed for their young has surprised many hunters. An Alaskan mammalogist observed a mother walrus use her tusks to break apart a large piece of ice to free her pup who had fallen into a crevice.

They can live to the age of at least 40. Because of their low rate of reproduction, compared with other pinnipeds, they have a relatively high survival rate. Mercury and organochlorine pesticides levels in walrus tissue in tissue from northern Baffin Bay are low compared to levels found in most other pinnipeds.

Two subspecies of walruses are recognized within the one living species: the Pacific walrus, O.rosmarus divergens , and the Atlantic walrus, O. rosmarus rosmarus . They are geographically isolated and have slight differences in cranial morphology and tusk characteristics. Some Soviet investigators recognize another subspecies found along the north coast of Asia, particularly in the Laptev Sea , O. rosmarus laptevi.

The Pacific walrus population is believed to have doubled between about 1960 and 1980 and reached a maximum population of more than 200,000. By 1978, the reproductive rate was declining as the population approached its environmental carrying capacity. The combined annual kill of walruses in Alaska and the former Soviet Union at least doubled during the early 1980s and it is now believed that the population is declining.

The North Atlantic populations did not make a similar recovery. There may only be from 1500 to 2000 walruses in the northeastern Atlantic today. Protection from commercial hunting since the early 1950s has lead to recolonizing the waters around Svalbard . The walrus population in Greenland's Thule district may be stable but the population off central west Greenland remains depleted.

Native people in all of the polar regions continue to hunt them with high-powered rifles and motorboats. Many shot walruses are not recovered and those that are recovered are used only for their ivory. Human occupation, whether it is Native villages, industrial sites or military installations, appear to endanger the terrestrial hauling out of the animals and some traditional grounds are no longer available to the walrus.

 

Lewis Carroll memorialized the walrus in:

The Walrus and the Carpenter from Through the Looking-Glass and What Alice Found There (1872)

" The time has come," the Walrus said,
To talk of many things:
Of shoes - and ships - and sealing wax
Of cabbages - and kings -
And why the sea is boiling hot -
And whether pigs have wings."

By Maris Sidenstecker I