Walruses (Odobenus rosmarus) are large semi-aquatic mammals that live in the cold Arctic seas of the Northern Hemisphere. There are six populations in the Arctic: four in the Atlantic Ocean, one in the Pacific Ocean, and one in the Laptev Sea. Two or three subspecies exist: Odobenus rosmarus rosmarus of the Atlantic, Odobenus r. divergens of the Pacific, and Odobenus r. laptevi of the Laptev Sea, considered by some to be a third subspecies. The Pacific walrus is slightly larger, with males weighing up to 2,045 kg (4,500 lb), but Atlantic males top out at 1,600 kg (3,500 lb). The walrus should not be confused with the elephant seal, another large pinniped, and despite the etymology of its name (variously attributed to combinations of the Dutch words for "whale" walvis and "horse" ros or "shore" wal and "giant" reus), it is not related to the whales. The most likely origin of the word is Old Norse hrossvalr "horse-whale", which was passed in a juxtaposed form to Dutch and the North-German dialects of the Hanseatic league as walros, Walross [Dansk Etymologisk Ordbog, Niels Age Nielsen, Gyldendal 1966].
Walruses are members of the order Carnivora and suborder (or
alternatively superfamily) Pinnipedia. . They are the only
members in the family Odobenidae. 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.
Closeup of a walrusWalruses divide their time between the water and beaches or ice floes, where they gather in large herds. They may spend several days at a time either on land or in the sea. Diving to depths of 90 m (300 ft), they sometimes stay under for as long as a half hour. They use their pectoral flippers to move along out of water and can stand on all fours with an awkward gait when on rough surfaces.
In the sea they sometimes catch fish, but generally graze along the sea bottom for clams which they suck from the shell. Pacific walruses feed on more than 60 genera of marine organisms including shrimp, crabs, tube worms, soft coral, tunicates, sea cucumbers, various mollusks, and even parts of other pinnipeds. Abrasion patterns of the tusks show that the tusks are dragged through the sediment but are not used to dig up prey and the upper edge of the snout is used instead. Walruses can also spit jets of water to look for clams. Clams and mollusks frequently form the large part of their diet. Large male walruses have been observed to attack seals if they cannot find any other food source.
Walruses have only two natural enemies: the orca and the polar bear. Polar bears hunt walruses by rushing at them, trying to get the herd to flee, then picking off calves or other stragglers. This is often a desperate action by the bear (done when it is either starved or ill), as the bear risks impalement by walrus tusks. A polar bear attack on a walrus herd was documented in the "Ice Worlds" episode of the critically acclaimed series, Planet Earth. In this case, a starving male bear was involved. Though the bear was successful in causing a frenzy within the walrus herd and separating a mid-sized female, it could not penetrate the thick walrus hide. Eventually all the walruses were able to escape into the ocean; the bear, however, met a tragic fate as it died from starvation and severe stab wounds.
Walruses use their long tusks (elongated canines) for fighting, dominance, and display and the males will spar with their tusks. They can also use them to form and maintain holes in the ice, or to anchor themselves with the ice.
Walruses have thick skin and it can get 5 cm (2 in) to 10 cm (4 in) thick around the neck and shoulders of males. The blubber of a male can be up to 6 in (15 cm) thick.
Walruses live around 50 years. The males reach sexual maturity around 10 years yet some as early as 7. They go into rut in January through April, increasing their food intake before the rut, yet then decreasing their food intake dramatically and eating only sporadically during the rut. The females can begin ovulating as soon as 4–6 years old. Interestingly the females are polyestrous, coming into heat in late summer and also around February, yet the males are only fertile around February so the animals are in practicality monoestrous. It is unclear why the females have this second season of potential fertility. By ten years old the females have reached maximum size and all are fertile by then. They breed in January to March with peak conception in February, and perhaps have a delayed implantation for a few months (4-5) with total gestation lasting 15–16 months. Walruses mate in the water and give birth on land or ice floes. The males show off in the water for the females who view them from pack ice. Males compete with each other aggressively for this display-space; the winners in these fights breed with large numbers of females. Older male walruses frequently bear large scars from these bloody but rarely fatal battles.
When a calf is born, it is over 1 m (3 ft) long and able to swim. The calves are born on the pack ice generally April to June and then generally nurse for 8–11 months before they begin eating fish on their own and can spend 3 to 5 years with the mothers.
About 200,000 Pacific walruses exist. Pacific walruses spend 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 in the Bering Strait, adjacent to the west shores of
Alaska, and in 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 Pacific walruses can have longer tusks and
About 15,000 Atlantic walruses exist: they live in the Canadian Arctic, in the waters of Greenland, of Svalbard and of the western portion of the Russian Arctic. 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, Atlantic Ocean) as being extirpated in Canada.
This Walrus Page is Copyright The Animal Web Guide © 2004 - 2009 Chuck Ayoub