The Atlantic Walrus
Walrus eating a tasty meal of seal
The walrus is one of the largest members of the Pinnipeds (the group which contains all types of seals and walrus), and is the largest member of this group to live in the Arctic. Two distinct subspecies are recognised: Atlantic and Pacific walrus. The Atlantic walrus is the slightly smaller of the two, with males reaching weights around of 1200 to 1500 kg and lengths of close to 3 m. Females are smaller than males, weighing up to around 600 - 700 kg and reaching lengths of 2.5 m (Born et al. 1995). A male Pacific walrus can weigh up to 1700 kg and be nearly 4 m long.
Walrus are a cinnamon-brown colour overall. After a long period in cold water, they may appear almost white, as blood vessels to the skin constrict to conserve body heat. In warmer weather animals can appear pink as blood vessels dilate and circulation increases to shed excess heat. A walrus' skin is very tough, and may be between 2 to 4 cm thick. It is thickest on the neck and shoulders of adult males, where it protects the animal against tusk jabs or bites from other males during fights for dominance. Under the skin lies a layer of insulating blubber, which can be up to 10 cm thick in places (Wiig et al. 2000). Both male and female walrus have long ivory tusks, which are modified upper canine teeth. Male walrus tusks tend to be longer and thicker than those of females. Another distinguishing feature of walrus is the presence of many stout vibrissae or whiskers on the snout. A walrus can have from 400 to 700 of these arranged in from 13 to 15 rows. The vibrissae are attached to muscles and are supplied with blood and nerves, and are used mainly to feel for food in bottom sediments.
Walrus are long-lived animals with a low reproductive rate. A walrus can live to be 40 years old. Females reach sexual maturity at from 4-10 years old, males at 6-10 years, although males likely cannot compete successfully for females until they are older, about 15 years of age. Mating takes place in the water, usually from January to April, and pregnancy lasts 15- 16 months. Females can only therefore give birth a maximum of once every two years, though it is more commonly 3 years between calves. This means that the walrus pregnancy rate is much lower than that of other pinnipeds.
Walrus calves are born on land or on the pack ice between late April and early June. The calf is nursed solely on milk for the first 6 months or so, before beginning to eat solid foods. Nursing mostly takes place in the water, but also sometimes on land or ice. The nursing period typically lasts for 2 years, with weaning occurring gradually over a period of time.
Distribution and stock definition
The walrus (Odobenus rosmarus) has a disjunct circumpolar distribution, with two subspecies recognised. Pacific walrus (O. r. divergens) inhabit the Bering, Chukchi, and Laptev seas, while Atlantic walrus (O. r. rosmarus L.) inhabit coastal areas of north-eastern Canada, Greenland and Svalbard. It has been proposed that the walrus in the Laptev Sea are a third subspecies, but this is questionable (Born et al. 1995).
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