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Walrus[1]
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Suborder: Caniformia
Superfamily: Pinnipedia
Family: Odobenidae
Allen, 1880
Genus: Odobenus
Brisson, 1762
Species: O. rosmarus
Binomial name
Odobenus rosmarus
(Linnaeus, 1758)
Subspecies

O. rosmarus rosmarus
O. rosmarus divergens
O. rosmarus laptevi (debated)

Distribution of walrus

The walrus (Odobenus rosmarus) is a large flippered marine mammal with a discontinuous circumpolar distribution in the Arctic Ocean and sub-Arctic seas of the Northern Hemisphere. The walrus is the only living species in the Odobenidae family and Odobenus genus. It is subdivided into three subspecies:[1] the Atlantic Walrus (O. rosmarus rosmarus) found in the Atlantic Ocean, the Pacific Walrus (O. rosmarus divergens) found in the Pacific Ocean, and O. rosmarus laptevi, found in the Laptev Sea.

The walrus is immediately recognized by its prominent tusks, whiskers and great bulk. Adult Pacific males can weigh up to 2,000 kilograms (4,400 lb) and, among pinnipeds, are exceeded in size only by the two species of elephant seals.[3] It resides primarily in shallow oceanic shelf habitat, spending a significant proportion of its life on sea ice in pursuit of its preferred diet of benthic bivalve mollusks. It is a relatively long-lived, social animal and is considered a keystone species in Arctic marine ecosystems.

The walrus has played a prominent role in the cultures of many indigenous Arctic peoples, who have hunted the walrus for its meat, fat, skin, tusks and bone. In the 19th and early 20th centuries, the walrus was the object of heavy commercial exploitation for blubber and ivory and its numbers declined rapidly. Its global population has since rebounded, though the Atlantic and Laptev populations remain fragmented and at historically depressed levels.

Contents

Etymology

The origin of walrus has variously been attributed to combinations of the Dutch words walvis ("whale") and ros ("horse")[4] or wal ("shore") and reus ("giant").[5] However, the most likely origin of the word is the Old Norse hrossvalr, meaning "horse-whale", which was passed in a juxtaposed form to Dutch and the North-German dialects as walros and Walross.[6]

The now archaic English word for walrus—morse—is widely supposed to have come from the Slavic.[7] Thus морж (morž) in Russian, mors in Polish, also mursu in Finnish, moršâ in Saami, later morse in French, morsa in Spanish, morsă in Romanian etc.

The compound Odobenus comes from odous (Greek for "tooth") and baino (Greek for "walk"), based on walrus observations using their tusks to pull themselves out of the water. The term divergens in Latin means "turning apart", referring to the tusks.

Taxonomy and evolution

The walrus is a mammal in the order Carnivora. It is the sole surviving member of the family Odobenidae, one of three lineages in the suborder Pinnipedia along with true seals (Phocidae), and eared seals (Otariidae). While there has been some debate as to whether all three lineages are monophyletic, i.e. descended from a single ancestor, or diphyletic, recent genetic evidence suggests that all three descended from a caniform ancestor most closely related to modern bears.[8] There remains uncertainty as to whether the odobenids diverged from the otariids before or after the phocids,[8] though the most recent molecular data synthesis suggests that phocids were the first to diverge.[9] What is known, however, is that Odobenidae was once a highly diverse and widespread family, including at least twenty species in the Imagotariinae, Dusignathinae and Odobeninae subfamilies.[10] The key distinguishing feature was the development of a squirt/suction feeding mechanism; tusks are a later feature specific to Odobeninae, of which the modern walrus is the last remaining (relict) species.

Two subspecies are commonly recognized: the Atlantic Walrus, O. r. rosmarus (Linnaeus, 1758) and the Pacific Walrus, O. r. divergens (Illiger, 1815). Fixed genetic differences between the Atlantic and Pacific subspecies indicate very restricted gene flow, but relatively recent separation, estimated at 500,000 and 785,000 years ago.[11] These dates coincide with the fossil-derived hypothesis that the walrus evolved from a tropical or sub-tropical ancestor that became isolated in the Atlantic Ocean and gradually adapted to colder conditions in the Arctic.[11] From there, it presumably re-colonized the North Pacific during high glaciation periods in the Pleistocene via the Central American Seaway.[9] An isolated population in the Laptev Sea is considered by some, including Russian biologists and the canonical Mammal Species of the World,[1] to be a third subspecies, O. r. laptevi (Chapskii, 1940), and is managed as such in Russia.[12] Where the subspecies separation is not accepted, whether to consider it a subpopulation of the Atlantic or Pacific subspecies remains under debate.[3][13]

Photo of several walruses, with prominently displayed white pairs of tusks
Young male Pacific Walruses on Cape Pierce in Alaska. Note the variation in the curvature and orientation of the tusks and the bumpy skin (bosses), typical of males.

Anatomy

Photo of walrus in ice-covered sea
Walrus using tusks to hang on breathing hole in the ice near St. Lawrence Island, Bering Sea
Drawing of walrus skeleton
Skeleton

While isolated Pacific males can weigh as much as 2,000 kg (4,400 lb), most weigh between 800 and 1,800 kg (1,800 and 4,000 lb). Females weigh about two-thirds as much, and the Atlantic subspecies weighs about 90% as much as the Pacific subspecies.[3] The Atlantic Walrus also tends to have relatively shorter tusks and somewhat more flattened snout. It is the second largest pinniped, after the elephant seals.

The walrus' body shape shares features with both sea lions (eared seals: Otariidae) and seals (true seals: Phocidae). As with otariids, it can turn its rear flippers forward and move on all fours; however, its swimming technique is more like that of true seals, relying less on flippers and more on sinuous whole body movements.[3] Also like phocids, it lacks external ears.

Tusks

The most prominent feature of the walrus is the long tusks. These are elongated canines, which are present in both sexes and can reach a length of 1 metre (3 ft 3 in) and weigh up to 5.4 kilograms (12 lb).[14] Tusks are slightly longer and thicker among males, who use them for fighting, dominance and display; the strongest males with the largest tusks typically dominate social groups. Tusks also form and maintain holes in the ice and haul out onto ice.[15] It was previously assumed that tusks were used to dig out prey from the seabed, but analyses of abrasion patterns on the tusks indicate that they are dragged through the sediment while the upper edge of the snout is used for digging.[16] The walrus has relatively few teeth other than the tusks, and typically has a dental formula of:

Dentition
1.1.3.0
0.1.3.0

Vibrissae

Surrounding the tusks is a broad mat of stiff bristles ('mystacial vibrissae'), giving the walrus a characteristic whiskered appearance. There can be 400 to 700 vibrissae in 13 to 15 rows reaching 30 centimetres (12 in) in length, though in the wild they are often worn to a much shorter length due to constant use in foraging.[17] The vibrissae are attached to muscles and are supplied with blood and nerves making them a highly sensitive organ capable of differentiating shapes 3 mm (0.12 in) thick and 2 mm (0.079 in) wide.[17]

Skin

Aside from the vibrissae, the walrus is sparsely covered with fur and appears bald. Its skin is highly wrinkled and thick, up to 10 cm (3.9 in) around the neck and shoulders of males. The blubber layer beneath is up to 15 cm (5.9 in) thick. Young walruses are deep brown and grow paler and more cinnamon-colored as they age. Old males, in particular, become nearly pink. Because skin blood vessels constrict in cold water, the walrus can appear almost white when swimming. As a secondary sexual characteristic, males also acquire significant nodules, called bosses, particularly around the neck and shoulders.[15]

The walrus has an air sac under its throat which acts like a flotation bubble and allows it to bob vertically in the water and sleep. The males possess a large baculum (penis bone), up to 63 cm (25 in) in length, the largest of any land mammal, both in absolute size and relative to body size.[3]

Life history

Photo of 5 walruses on rocky shore
Walruses fighting

Reproduction

Walruses live to about 20–30 years old in the wild.[18] The males reach sexual maturity as early as 7 years, but do not typically mate until fully developed around 15 years of age.[3] They rut from January through April, decreasing their food intake dramatically. The females begin ovulating as soon as 4–6 years old.[3] The females are polyestrous, coming into heat in late summer and also around February, yet the males are fertile only around February; the potential fertility of this second period is unknown. Breeding occurs from January to March, peaking in February. Males aggregate in the water around ice-bound groups of estrous females and engage in competitive vocal displays.[19] The females join them and copulate in the water.[15]

Gestation lasts 15 to 16 months. The first 3 to 4 months are spent with the blastula in suspended development before it implants itself in the placenta. This strategy of delayed implantation, common among pinnipeds, presumably evolved to optimize both the mating season and the birthing season, determined by ecological conditions that promote newborn survival.[20] Calves are born during the spring migration, from April to June. They weigh 45–75 kg (99–170 lb) at birth and are able to swim. The mothers nurse for over a year before weaning, but the young can spend up to 3 to 5 years with the mothers.[15] Because ovulation is suppressed until the calf is weaned, females give birth at most every two years, leaving the walrus with the lowest reproductive rate of any pinniped.[21]

Migration

The rest of the year (late summer and fall) the walrus tends to form massive aggregations of tens of thousands of individuals on rocky beaches or outcrops. The migration between the ice and the beach can be long distance and dramatic. In late spring and summer, for example, several hundred thousand Pacific Walruses migrate from the Bering sea into the Chukchi sea through the relatively narrow Bering Strait.[15]

Ecology

Range and habitat

Photo of hundreds of animals, lying on the ground
Walrus colony

The majority of the Pacific Walrus population summers north of the Bering Strait in the Chukchi Sea along the north shore of eastern Siberia, around Wrangel Island, in the Beaufort Sea along the north shore of Alaska, and in the waters between those locations. Smaller numbers of males summer in the Gulf of Anadyr on the south shore of Siberia's Chukchi Peninsula and in Bristol Bay off the south shore of southern Alaska west of the Alaska Peninsula. In the spring and fall they congregate throughout the Bering Strait, reaching from the west shores of Alaska to the Gulf of Anadyr. They winter in the Bering Sea along the eastern shore of Siberia south to the northern part of the Kamchatka Peninsula, and along Alaska's southern shore.[3] A 28,000 year old fossil walrus specimen was dredged out of San Francisco Bay, indicating that the Pacific Walrus ranged far south during the last ice age.[22]

The much smaller Atlantic population ranges from the Canadian Arctic, Greenland, Svalbard and the western portion of the Russian Arctic. There are eight presumed sub-populations based largely on geographical distribution and movement data, five to the west of Greenland and three to the east.[23] The Atlantic Walrus once ranged south to Cape Cod and occurred in large numbers in the Gulf of St. Lawrence. In April 2006, the Canadian Species at Risk Act listed the Northwest Atlantic Walrus population (Québec, New Brunswick, Nova Scotia, Newfoundland and Labrador) as being extirpated in Canada.[24]

The isolated Laptev population is confined year-round to the central and western regions of the Laptev Sea, the easternmost regions of the Kara Sea, and the westernmost regions of the East Siberian Sea. Current populations are estimated to be between 5,000 and 10,000 individuals.[25]

Their limited diving ability brings them to depend on shallow waters (and appropriate nearby ice coverage) to enable them to reach their preferred benthic prey.

Population

There were roughly 200,000 Pacific Walruses according to the most recent (1990) census-based estimate.[26][27]

The Atlantic Walrus was nearly eradicated by commercial harvest and has a much smaller population. Good estimates are difficult to obtain, but the total population is probably below 20,000.[28][29]

Diet

Photo of walrus head in profile showing one eye, nose, tusks, and "mustache"
Vibrissae of captive walrus (Japan)
Photo of two walruses in shallow water facing shore
Walruses leaving the water

Walruses prefer shallow shelf regions and forage primarily on the sea floor, often from sea ice platforms.[3] They are not particularly deep divers compared to other pinnipeds: the deepest recorded dives are around 80 metres (260 ft). They can remain submerged for as long as half an hour.[30]

The walrus has a diverse and opportunistic diet, feeding on more than 60 genera of marine organisms including shrimps, crabs, tube worms, soft corals, tunicates, sea cucumbers, various mollusks, and even parts of other pinnipeds.[31] However, it prefers benthic bivalve mollusks, especially clams, for which it forages by grazing along the sea bottom, searching and identifying prey with its sensitive vibrissae and clearing the murky bottoms with jets of water and active flipper movements.[32] The walrus sucks the meat out by sealing its powerful lips to the organism and withdrawing its tongue, piston-like, rapidly into its mouth, creating a vacuum. The walrus palate is uniquely vaulted, enabling effective suction.

Aside from the large numbers of organisms actually consumed by the walrus, its foraging has a large peripheral impact on benthic communities. It disturbs (bioturbates) the sea floor, releasing nutrients into the water column, encouraging mixing and movement of many organisms and increasing the patchiness of the benthos.[16]

Seal tissue has been observed in fairly significant proportion of walrus stomachs in the Pacific, but the importance of seals in the walrus diet is under debate.[33] There have been rare documented incidents of predation on seabirds, particularly the Brünnich's Guillemot Uria lomvia.[34]

Predation

Due to its great size, the walrus has only two natural predators: the orca and the polar bear. It does not, however, comprise a significant component of either predator's diet. The polar bear hunts the walrus by rushing at beached aggregations and consuming individuals that are crushed or wounded in the sudden exodus, typically younger or infirm animals.[35] However, even an injured walrus is a formidable opponent for a polar bear, and direct attacks are rare.

Relation to humans

Conservation

Siberian Yupik woman holding walrus tusks
Photo of section of tusk
Walrus tusk engraving made by Chukchi artisans depicting polar bears attacking walruses. On display in the Magadan Regional Museum, Magadan, Russia

In the 18th and 19th centuries, the walrus was heavily exploited by American and European sealers and whalers, leading to the near extirpation of the Atlantic population.[36] Commercial walrus harvesting is now outlawed throughout its range, although Chukchi, Yupik and Inuit peoples,[37] continue to kill small numbers towards the end of each summer.

Traditional hunters used all parts of the walrus.[38] The meat, often preserved, is an important winter nutrition source; the flippers are fermented and stored as a delicacy until spring; tusks and bone were historically used for tools as well as material for handicrafts; the oil was rendered for warmth and light; the tough hide made rope and house and boat coverings; the intestines and gut linings made waterproof parkas; etc. While some of these uses have faded with access to alternative technologies, walrus meat remains an important part of local diets,[39] and tusk carving and engraving remain a vital art form.

Walrus hunts are regulated by resource managers in Russia, the United States, Canada and Denmark and representatives of the respective hunting communities. An estimated 4-7,000 Pacific Walruses are harvested in Alaska and Russia, including a significant portion (approx. 42%) of struck and lost animals.[40] Several hundred are removed annually around Greenland.[41] The sustainability of these levels of harvest is difficult to determine given uncertain population estimates and parameters such as fecundity and mortality.

The effects of global climate change is another element of concern. The extent and thickness of the pack ice has reached unusually low levels in several recent years. The walrus relies on this ice while giving birth and aggregating in the reproductive period. Thinner pack ice over the Bering Sea has reduced the amount of resting habitat near optimal feeding grounds. This more widely separates lactating females from their calves, increasing nutritional stress for the young and lower reproductive rates.[42] Reduced coastal sea ice has also been implicated in the increase of stampeding deaths crowding the shorelines of the Chukchi Sea between eastern Russia and western Alaska.[43][44] However, there is insufficient climate data to make reliable predictions on population trends.

Currently, two of the three walrus subspecies are listed as "least-concern" by the IUCN, while the third is "data deficient".[2] The Pacific Walrus is not listed as "depleted" according to the Marine Mammal Protection Act nor as "threatened" or "endangered" under the Endangered Species Act. The Russian Atlantic and Laptev Sea populations are classified as Category 2 (decreasing) and Category 3 (rare) in the Russian Red Book.[25] Global trade in walrus ivory is restricted according to a CITES Appendix 3 listing.

Culture

Photo of 2 masks. In the center is the image of a face, surrounded by a ring, in turn surrounded by 8 white rectangular pieces
Walrus Ivory masks made by Yupik in Alaska

The walrus plays an important role in the religion and folklore of many Arctic peoples. Skin and bone are used in some ceremonies and the animal appears frequently in legends. For example, in a Chukchi version of the widespread myth of the Raven, in which Raven recovers the sun and the moon from an evil spirit by seducing his daughter, the angry father throws the daughter from a high cliff and, as she drops into the water, she turns into a walrus — possibly the original walrus. According to various legends, the tusks are formed either by the trails of mucus from the weeping girl or her long braids.[45] This myth is possibly related to the Chukchi myth of the old walrus-headed woman who rules the bottom of the sea, who is in turn linked to the Inuit goddess Sedna. Both in Chukotka and Alaska, the aurora borealis is believed to be a special world inhabited by those who died by violence, the changing rays representing deceased souls playing ball with a walrus head.[45][46]

Because of its distinctive appearance, great bulk and immediately recognizable whiskers and tusks, the walrus also appears in the popular cultures of peoples with little direct experience with the animal, particularly in English children's literature. Perhaps its best known appearance is in Lewis Carroll's whimsical poem The Walrus and the Carpenter that appears in his 1871 book Through the Looking-Glass. In the poem, the eponymous anti-heroes use trickery to consume a great number of oysters. Although Carroll accurately portrays the biological walrus's appetite for bivalve mollusks, oysters, primarily nearshore and intertidal inhabitants, in fact comprise an insignificant portion of its diet, even in captivity.[47]

Another appearance of the walrus in literature is in the story The White Seal in Rudyard Kipling's The Jungle Book, where it is the "old Sea Vitch—the big, ugly, bloated, pimpled, fat-necked, long-tusked walrus of the North Pacific, who has no manners except when he is asleep".[48]

References

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  43. ^ http://www.nytimes.com/2009/10/03/science/earth/03walrus.html?ref=todayspaper NY Times, Global warming could reverse a walrus comeback, 3 Oct 2009
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1911 encyclopedia

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From LoveToKnow 1911

WALRUS, or Morse (Odobaenus rosmarus), a large marine mammal allied to the seals, representing a family by itself. The former word is a modification of the Scandinavian vallross or hvalros (" whale-horse"), the latter an adaptation of the Russian name for the animal. A full-grown male walrus measures from 10 to 11 ft. from the nose to the end of the short tail, and is a heavy, bulky animal, especially thick about the shoulders. The head is rounded, the eyes are rather small, and there are no external ears. The muzzle is short and broad, with, on each side, a group of stiff, bristly whiskers, which become stouter and shorter in old animals. The tail scarcely projects beyond the skin. The fore-limbs are free only from the elbow; the foreflipper is broad, flat and webbed, the five digits being of nearly equal length, but the first slightly the longest. Each digit has a small flattened nail, situated on the inner surface at a considerable distance from the end. The hind-limbs are enclosed in the skin of the body, almost to the heel. The free portion when expanded is fan-shaped, the two outer toes (first and fifth) being the longest, especially the latter. Flaps of skin project considerably beyond the bones of the toes. The nails of the first and fifth toes are minute and flattened; those of the second, third and fourth elongated, sub-compressed and pointed. The soles of both fore and hind feet are bare, rough and warty. The surface of the skin generally is covered with short, adpressed hair of a light yellowish-brown colour, which, on the under parts of the body and base of the flippers, passes into dark reddish-brown or chestnut. In old animals the hair becomes more scanty, sometimes almost disappearing, and the skin shows evidence of the rough life and pugnacious habits of the animal in the scars with which it is usually covered. It is everywhere more or less wrinkled, especially over the shoulders, where it is thrown into deep and heavy folds.

One of the most striking characteristics of the walrus is the pair of tusks which descend almost directly downwards from the upper jaw, sometimes attaining a length of 20 in. or more. In the female they are as long or sometimes longer than in the male, but less massive. In the young of the first year they are not visible. These tusks correspond to the canine teeth of other mammals. All the other teeth, including the lower canines, are much alike - small, simple and one-rooted, and with crowns, rounded at first, but wearing to a flat or concave surface. Many of the teeth are lost early, or remain through life in a rudimentary state concealed beneath the gum. The tusks are formidable weapons of defence, but their principal use seems to be scraping and digging among sand and shingle for the molluscs and crustaceans on which the walrus feeds. They are said also to aid in climbing up the slippery rocks and ledges of ice on which so much of the animal's life is passed.

Walruses are more or less gregarious in their habits, being met with generally in companies or herds of various sizes. They are only found near the coast or on large masses of floating ice, and rarely far out in the open sea; and, though often moving from one part of their feeding-ground to another, have no regular migrations. Their young are born between April and June, The Atlantic Walrus (Odobaenus rosmarus). usually but one at a time, never more than two. Their strong affection for their young, and their sympathy for each other in danger, have been noticed by all who have had the opportunity of observing them in their haunts. When one is wounded the whole herd usually join in defence. Although harmless and inoffensive when not molested, they exhibit considerable fierceness when attacked, using their tusks with tremendous effect either on human enemies who come into too close quarters or on polar bears, the only other adversary they can meet with in their own natural territory. The voice, a loud roaring, which can be heard at a great distance, is described by Dr Kane as "something between the mooing of a cow and the deepest baying of a mastiff, very round and full, with its bark or detached notes repeated rather quickly seven or nine times in succession." The principal food of the walrus consists of bivalve molluscs, especially Mya truncata and Saxicava rugosa, two, species very abundant in the Arctic regions, which it digs up from the mud and sand in which they lie buried at the bottom of the sea by means of its tusks. It crushes and removes the shells by the aid of its grinding teeth and tongue, and swallows only the soft parts of the animal. It also feeds on other molluscs, sand-worms, starfishes and shrimps. Portions of various kinds of seaweed have been found in its stomach, but whether swallowed intentionally or not is doubtful.

The commercial products of the walrus are its oil, hide (used to manufacture harness and sole-leather and twisted into tillerropes) and tusks. The ivory of the latter is, however, inferior in quality to that of the elephant. Its flesh forms an important article of food to the Eskimo and Chukchi. Of the coast tribes of the last-named people the walrus formed the chief means of support.

Walruses are confined to the northern circumpolar regions, extending apparently as far north as explorers have penetrated. On the Atlantic coast of America the Atlantic species was met with in the 16th century as low as the southern coast of Nova Scotia, and in the last century was common in the Gulf of St Lawrence and on the shores of Labrador. It still inhabits the coast round Hudson's Bay, Davis Strait and Greenland, where, however, its numbers are decreasing. It is not found on the Arctic coast of America between the 97th and r 58th meridians. In Europe, occasional stragglers have reached the British Isles; and it was formerly abundant on the coasts of Finmark. It is rare in Iceland, but Spitzbergen, Novaia Zemblia and the western part of the north coast of Siberia are constant places of resort. The North Pacific, including both sides of Bering Strait, northern Kamchatka, Alaska and the Pribyloff Islands are also the haunts of numerous walruses, which are isolated from those of the North Atlantic by long stretches of coast in Siberia and North America where they do not occur. The Pacific walrus appears to be as large as, if not larger than, that of the Atlantic; its tusks are longer and more slender, and curved inwards; and the whiskers are smaller, and the muzzle relatively deeper and broader. These and certain other differences have led to its being considered specifically distinct, under the name of Odobaenus obesus. Its habits appear to be similar to those of the Atlantic form. Though formerly found in immense herds, it is becoming scarce, as the methods of destruction used by American whalers are more certain than those of the Chukchi, to whom the walrus long afforded the principal means of subsistence.

Fossil remains of walruses and closely allied animals have been found in the United States, and in England, Belgium and France, in deposits of late Tertiary age. (W. H. F.; R. L.*)


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Simple English

Walrus[1]
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Suborder: Caniformia
Superfamily: Pinnipedia
Family: Odobenidae
Allen, 1880
Genus: Odobenus
Brisson, 1762
Species: O. rosmarus
Binomial name
Odobenus rosmarus
(Linnaeus, 1758)
File:Odobenus rosmarus
Distribution of Walrus
Subspecies

O. rosmarus rosmarus
O. rosmarus divergens
O. rosmarus laptevi (debated)

A walrus is a marine mammal, the only species of the family Odobenidae, which is one of the three pinniped families. They live in the cold northern seas around North America and Europe.

Contents

Description

Walruses have lots of things similar to true seals and eared seals. Like true seals, they just have a hole for an ear - not ear flaps. Like eared seals, they can rotate their back flippers forward to walk on land. Like both true seals and eared seals, they are very good swimmers and divers. However, walruses do have some features that neither true seals nor eared seals have.

The most famous thing about walruses are their tusks (but even though they are called tusks, they are actually teeth growing out of their mouth, a bit like the narwhal). Walruses have very long teeth that grow out of their mouths. The tusks grow for about 15 years before they reach their full length, which is about 40 inches for males and 30 for females.

With most mammals, only the male grows tusks, but both the male and female walrus grow tusks because they are very important. They can use it to protect themselves from polar bears and killer whales, and use them when the eat: for instance, when they eat bigger prey such as seals and small whales, they first tear them apart with their tusks to make them easier to eat. Another important use of a walrus's tusks is to help itself haul out. Pushing its tusks into the ice, the walrus gets extra help hauling its enormous (really big) body out of the sea. This is probably how walruses got their family name Odobenidae, which comes from Greek words meaning "one that walks with teeth." They do not walk with their teeth, but it can look as if they do when they pull themselves out of the water. Their tusks can also be used to cut holes in the ice. They also sometimes sleep with their tusks anchored into the ice (probably so they will not slip around when walruses push each other for a nicer place to sleep). Of course, males also use their tusks to fight with other males. [3]

Walruses are very big, even compared to big male sea lions. When they are all grown up, they can weigh more than 3,000 pounds. The walruses that live in the Atlantic Ocean are a little smaller than the ones in the Pacific Ocean. Both kinds like to stay in the cold north. With all their blubber, which can be as much as six inches thick, they are very comfortable in icy water.

Changing Colors

Walruses can change colors depending on how warm they are. They are usually different kinds of brown, but as they get warmer, their skin can turn pink. This is because as they get warmer, blood rushes to the skin to try to cool it. The extra blood makes the skin look pink. When they are really cold, their skin can almost turn white. This is because as the skin gets very cold, the animal's body makes the blood go away from the skin. Without blood, the skin's color gets lighter.

References

  1. Wozencraft, W. C. (16 November 2005). Wilson, D. E., and Reeder, D. M. (eds). ed. Mammal Species of the World (3rd edition ed.). Johns Hopkins University Press. ISBN 0-8018-8221-4. http://www.bucknell.edu/msw3. 
  2. Seal Specialist Group (1996). Odobenus rosmarus. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 12 May 2006.
  3. Exploring Creation with Zoology 2 by Jeannie K. Fulbright, p. 48

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