Walrus - Four Brothers
The walrus (Odobenus rosmarus) is circumpolar in its range but they are found in geographically separate areas. The only living species in the Odobenidae family and Odobenus genus, the walrus is divided into three subspecies; the Atlantic (O. rosmarus rosmarus) which inhabits the coastal regions of northeastern Canada and Greenland, the Pacific Walrus (O. rosmarus divergens) found in the Bering and Chukchi Seas, and O. rosmarus Laptevi, which lives in the Laptev Sea. The walrus is immediately recognized by its prominent tusks, whiskers and great bulk. Adult Pacific males can weigh up to 3,700 lb (1,700 kilograms). They are long-lived, social animal and considered a keystone species. Walruses are cinnamon brown in color. They are able to turn their hind flippers forward to aid in movement on land. Their front flippers are large and each has five digits. Males have special air sacs that are used to make a bell-like sound. The origin of 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 an inverted form to Dutch and the North-German dialects as walros and Walross. 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. The walrus has played a prominent role in the cultures of many Arctic peoples, who have depended on them for meat, fat, skin, tusks and bone. In the 19th and early 20th centuries, the object of heavy commercial exploitation for blubber and ivory, walrus numbers declined rapidly. The global population has since rebounded, though the Atlantic and Laptev populations remain fragmented and at historically depressed levels. There were roughly 200,000 Pacific Walruses according to the most recent (1990) census-based estimate. 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. Tusks and dentition 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 3 ft (1 meter) and weigh up to 12 lb (5.4 kilograms). 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. 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. While the dentition of walruses is highly variable, they generally have relatively few teeth other than the tusks. The maximal number of teeth is 38 with dentition formula, but over half of the teeth are rudimentary and occur with less than 50% frequency, such that a typical dentition includes only 18 teeth 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.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. 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. Males also acquire significant nodules, called bosses, particularly around the neck and shoulders. The walrus has an air sac under the throat which acts like a floatation bubble and allows it to bob vertically in the water and sleep. 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. 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. 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. 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 (Quebec, 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. Diet Due to heir limited diving ability (and appropriate nearby ice cover) walrus prefer shallow shelf regions and forage primarily on the sea floor, often from sea ice platforms.The deepest recorded dives are around 80 metres (260 ft). They can remain submerged for as long as half an hour. The walrus has a diverse and opportunistic diet, feeding on more than 60 genera of marine organisms including shrimp, crabs, tube worms, soft corals, tunicates, sea cucumbers, various mollusks, and even parts of other pinnipeds (seals). 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.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 the sea floor, releasing nutrients into the water column, encouraging mixing and movement of many organisms and increasing the patchiness of the benthos. 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.There have been rare documented incidents of predation on seabirds, particularly the Brunnich's Guillemot. Predation Due to its great size, the walrus has only two natural predators: the orca and 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.However, even an injured walrus is a formidable opponent for a polar bear, and direct attacks are rare. Relation to humans Conservation 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 walrus harvesting is now outlawed throughout its range, although Chukchi, Yupik and Inuit peoples, continue to kill small numbers towards the end of each summer. Traditional hunters used all parts of the walrus. 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,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. Several hundred are removed annually around Greenland. 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 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. 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.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". 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. Global trade in walrus ivory is restricted according to a CITES Appendix 3 listing. Culture 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 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. 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, 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. 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". Walruses also appear in the songs I AmTthe Walrus and Glass Onion by The Beatles. Diet Walrus staples include clams, mussels and other bottom dwelling (or benthic) organisms that they locate through their whiskers. They are also known to eat carcasses of young seals when food is scarce. Behavior Walruses are very social animals and congregate in large numbers. They haul out in herds and males and females form separate herds during the non-breeding season. They establish dominance through threat displays involving tusks, bodies and aggression. The largest walruses are the most aggressive. Walruses spend two thirds of their lives in the water. Most walrus groups migrate north in the summer and south in the winter, and females haul out on the ice to give birth. Due to its great size, the walrus has only two natural predators: the orca (or killer whale) and the polar bear. Reproduction Mating Season: December to March Gestation:15-16 months Offspring: Generally 1 calf, though twins have been recorded. Calves are ashen gray to brown in color and weigh in from about 99-165 lbs at birth. They turn reddish brown within a few weeks and grow rapidly on their mothers’ milk. Females with young calves gather in ‘nursery herds’ to help one another raise their young. Calves are weaned from their mother at about two years of age. Climate Change and Other Threats Historically, walruses were hunted commercially for their ivory tusks, oil and hides. Today they are hunted to a lesser degree. The biggest threat facing walruses today is climate change. Walruses feed on the ocean floor in the relatively shallow waters of the continental shelf, where the sea ice itself sustains a rich food web. Algae grow in long trailing strands at the edge of the ice and in the nearby waters. These algae are eaten by tiny animals called zooplankton, which in turn feed larger animals. At every step along the way, particles of food and nutrients “rain” down onto the ocean floor, sustaining the massive beds of mollusks on which walruses feast. Females with leave their young in safety on the sea ice while they forage, then haul out to nurse their calves. The accelerating retreat of sea ice puts the newborns’ safe haven farther away from the mothers’ food—meaning long, exhausting swims for the mothers, and more time alone for the calves.