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Last updated on April 20, 2014 at 17:20 EDT

Walrus

Walruses are large semi-aquatic mammals that live in the cold Arctic seas of the Northern Hemisphere. There are 6 populations in the arctic and 2 or 3 subspecies exist. The Pacific walrus is slightly larger, with males weighing up to 4,180 lb (1,900 kg), but Atlantic males top out at 3,500 lb (1,600 kg). The walrus should not be confused with the elephant seal.

Walruses are members of the order Carnivora and suborder (or alternatively super family) Pinnipedia. They are the only members in the family Odobenidae.

Lifestyle and feeding

Walruses spend about half their time in the water and half their time 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 300 ft (90 m), 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, tubeworms, 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 three natural enemies that are humans, 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. Walruses have been known to kill polar bears.

The walruses use their long tusks (elongated canines) for fighting, dominance, and display. 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.

Physical description and life cycle

Walruses have thick skin and it can get to 2 inches (5cm) thick around the neck and shoulders of males. The 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 thru April, increasing their food intake before the rut. They then decrease their food intake dramatically and eating only sporadically during the rut. The females can begin ovulating as soon as 4 to 6 years old. Interestingly the females are polyestrous, coming into heat in late summer and also around February. 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. 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 3 feet (1 m) long and able to swim. The calves are born on the pack ice generally April to June. They generally nurse for 8 to 11 months before they begin eating fish on their own and can spend 3 to 5 years with the mothers.

Pacific

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. They also stay around Wrangel Island, in the Beaufort Sea along the north shore of Alaska, and in the waters between those locations. Smaller numbers of males spend the 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 spend the 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 smaller noses.

Atlantic

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.

Traditional hunting

Alaska Natives slaughter about 3,000 walruses annually. Humans use ivory from the tusks for carving. The natives call the penis bone of male an oosik and use it in making knives. Federal laws in both the USA and in Canada protect walruses and set quotas on the yearly harvest. Only under rare circumstances may non-native hunters gain permission to kill a walrus legally. The law prohibits the export of raw tusks from Alaska, but walrus-ivory products may come on the market if first sculpted into scrimshaw by a native craftsman.

Medical problems

Eye problems for the walrus are common and they sometimes experience intestinal disease. They sometimes get tusk infections, and in captivity are prone to ingesting foreign objects. Also various common fungal and bacterial sometimes cause minor infections. Trampling and tusk injuries occur during interactions and sometimes females are harassed and show bruises and laceration.

Walrus