English

Noun

walruses

1. Plural 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: and, among pinnipeds, are exceeded in size only by the two species of elephant seals. 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.

Etymology

The origins of the word "walrus" has variously been attributed to combinations of the Dutch words walvis ("whale") and ros ("horse") or wal ("shore") and reus ("giant"). 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 of the Hanseatic League as walros and Walross.

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

The compound Odobenus comes from odous (Greek for "tooth") and baino (Greek for "walk"), based on observations of walruses using their tusks to pull themselves out of the water. 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 members 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. There remains uncertainty as to whether the odobenids diverged from the otariids before or after the phocids, What is known, however, is that Odobenidae was once a highly diverse and widespread family, including at least twenty known species in the Imagotariinae, Dusignathinae and Odobeninae subfamilies. 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 of the Walrus are commonly recognized: the Atlantic Walrus, O. r. rosmarus (Illiger, 1815) and the Pacific Walrus, O. r. divergens (Linnaeus, 1758). Fixed genetic differences between the Atlantic and Pacific subspecies indicate very restricted gene flow, but relatively recent separation, estimated to have occurred 500,000 and 785,000 years ago. 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. Where the subspecies separation is not accepted, there remains debate as to whether it should be considered a subpopulation of the Atlantic or Pacific subspecies. the majority of the Pacific Walrus population spends the summer 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 the Chukchi Peninsula of Siberia 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 to the south in the Bering Sea along the eastern shore of Siberia south to the northern part of the Kamchatka Peninsula, and along the southern shore of Alaska.

The Atlantic Walrus, which was nearly decimated by commercial harvest, is much smaller. Good estimates are difficult to obtain, but the total number is probably below 20,000. It ranges from the Canadian Arctic, Greenland, Svalbard and the western portion of the Russian Arctic. There are eight presumed sub-populations of the Atlantic Walrus based largely on geographical distribution and movement data, five to the west and three to the east of Greenland. The Atlantic Walrus once enjoyed a range that extended 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.

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.

Description

While isolated Pacific males can weigh as much as , most weigh between and . Females weigh about two thirds as much as males, and the Atlantic subspecies is about 90% as massive as the Pacific subspecies. These are slightly longer and thicker among males, who use them for fighting, dominance and display; the strongest males with the largest tusks typically dominating social groups. Tusks are also used to form and maintain holes in the ice and haul out onto ice. It was previously assumed that tusks were used to dig out prey items 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. The Walrus has relatively few teeth other than the great canine tusks, and typically has a dental formula of:

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 in length, though in the wild they are often worn to a much shorter length due to constant use in foraging. The vibrissae are attached to muscles and are supplied with blood and nerves making the vibrissal array a highly sensitive organ capable of differentiating shapes thick and wide. The females join them and copulation occurs in the water. The calves are born during the spring migration from April to June. They weigh to 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.

In the non-reproductive season (late summer and fall) the Walrus tends to migrate away from the ice and form massive aggregations of tens of thousands of individuals on rocky beaches or outcrops. The nature of the migration between the reproductive period and the summer period can be a rather 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.

The Walrus has a highly 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. However, it displays great preference for benthic bivalve mollusks, especially species of 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. The Walrus sucks the meat out by sealing the organism in the powerful lips and drawing the tongue, piston-like, rapidly into the mouth, creating a vacuum. The Walrus palate is uniquely vaulted, allowing for extremely effective suction to be generated by the tongue.

Aside from the large numbers of organisms actually consumed by the Walrus, it has a large peripheral impact on the benthic communities while foraging. 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. There have been rare documented incidents of predation on seabirds, particularly the Brünnich's Guillemot Uria lomvia.

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 those individuals that are crushed or wounded in the sudden mass exodus, typically younger or infirm animals. However, even an injured Walrus is a formidable opponent for a Polar Bear, and direct attacks are rare.

Exploitation and status

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. Commercial harvest of the Walrus is now outlawed throughout its range, though a traditional subsistence hunt continues among Chukchi, Yupik and Inuit peoples. The Walrus hunt occurs towards the end of the summer. Traditionally, all parts of the walrus was used. The meat, often preserved, is an important source of nutrition through the winter; 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 is used for rope and house and boat coverings; the intestines and gut linings are used for making waterproof parkas; etc. While some of these uses have faded with access to alternative technologies, walrus meat remains an important part of local diets, and tusk carving and engraving remain a vital art form among many communities.

Walrus hunts are regulated by resource managers in Russia, the U.S., Canada and Denmark and representatives of the respective Walrus hunting communities. An estimated four to seven thousand Pacific Walruses are harvested in Alaska and Russia, including a significant portion (approx. 42%) of struck and lost animals. Several hundred are removed annually around Greenland. The sustainability of these levels of harvest are difficult to determine since there is considerable uncertainty in the population estimates themselves and in the population parameters such as fecundity and mortality.

The effects of global climate change on the Walrus populations is another element of concern. In particular, there have been well-documented reductions on the extent and thickness of the pack ice which the Walrus relies on as a substrate for giving birth and aggregating in the reproductive period. It is hypothesized that thinner pack ice over the Bering Sea has reduced the amount of suitable resting habitat near optimal feeding grounds. This causes greater separation of lactating females from their calves leading to nutritional stress for the young or lower reproductive rates for the females. However, there is as yet little data to make reliable predictions on the impacts of changing climate conditions on total population trends.

Currently, two of the three Walrus subspecies are listed as "least-concern" by the IUCN, while the third is "data deficient". Global trade in Walrus ivory is restricted according to a CITES Appendix 3 listing.

Folklore and culture

The Walrus plays an important role in the religion and folklore of many Arctic peoples. The skin and bones are used in some ceremonies and the animal itself 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 versions, the tusks are formed either by the trails of mucus from the weeping girl or her long braids. 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.

Because of its distinctive appearance and immediately recognizable whiskers and tusks, the Walrus also appears in the popular cultures of peoples with little immediate experience with the animal, most often in children's literature. Perhaps its best known appearance is in Lewis Carroll's whimsical poem The Walrus and the Carpenter that appears in his book Through the Looking-Glass (1871). 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 do not naturally occur within the Arctic and sub-Arctic range of the Walrus.

The Walrus from Lewis Carroll's poem was the inspriation for The Beatles song I Am the Walrus, written by John Lennon. Lennon referred to the song, and the Walrus, in two other songs, Glass Onion and God. Paul McCartney is dressed as a Walrus on the cover of The Beatles' album on which I am the Walrus appears, Magical Mystery Tour, while Lennon himself appeared in Walrus drag in the film of the song that appears in the Magical Mystery Tour movie. At the time the song appeared, and years before Lennon himself explained that the Carroll poem was the genesis of the song, there was speculation on what the Walrus symbolized in The Beatles song. During the "Paul is Dead" imbroglio, journalist John Neary, the author of the cover story "The Magical McCartney Mystery" in LIFE Magazine's November 7, 1969 issue, incorrectly claimed that the "black walrus was a folk symbol of death."

Other examples of appearance of the animal in the popular culture include The Jungle Book story by Rudyard Kipling, 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" who tells the white seal Kotick where to seek advice for his mission.

See also

portalpar Mammals

• Arctic ecology
• Imagotaria downsi

References

• Marine Mammal Medicine, Leslie Dierauf and Frances Gulland, CRC Press 2001, ISBN 0-8493-0839-9
• Annales des sciences naturelles. Zoologie et biologie animale. Paris, Masson. ser.10:t.7
• Tagging and tracking Atlantic walrus (BBC Walrus tracker).