Nomenclature

Two subspecies are commonly recognized: the Atlantic walrus, Odobenus rosmarus rosmarus (Linnaeus, 1758), and the Pacific walrus, Odobenus rosmarus divergens (Illiger, 1815). A third subspecies has been proposed, the Laptev Sea walrus, Odobenus rosmarus laptevi (Chapski, 1940), but this is not commonly recognized as such.

Appearance

The walrus is a very large and robust pinniped, with a cinnamon-brown skin, which becomes lighter with age. The skin is covered with short coarse hair. The walrus' most distinctive features are the large tusks (enlarged upper canine teeth). Of the Atlantic subspecies, the males measure 300 cm and weigh 1,200 kg. Females measure 250 cm and weigh 750 kg. At birth pups are 140 cm long and weigh 50 kg. The Pacific walrus is slightly larger: males are 360 cm long and weigh 1600 kg, female are 260 cm long and weigh 1250 kg and pups measure 140 cm and weigh 60 kg.

Distribution

Both the Atlantic and the Pacific walrus each inhabit two distinct areas:

1. East Greenland, Spitsbergen, Franz Josephland, Barents Sea and Kara Sea (Atlantic walrus)
2. East Canadian Arctic and West Greenland (Atlantic walrus)
3. Bering Sea and Chukchi Sea (Pacific walrus)
4. Laptev Sea (Pacific walrus)

Feeding

The walrus feeds mainly on benthic invertebrates, such as molluscs, echinoderms and crustaceans. They eat upto 45 kg per day.

Population dynamics and life history

Females become mature at ages 5 through 7, males at 5 through 10. 80% of the females calve every 2 years, 15% every 3 years and 5% less frequently. Gestation lasts 15 months, including a delay of implantation of 3-3½ months. Lactation lasts 1 to 2 years. Longevity is about 40 years. The mortality rate for the Pacific walrus is 5%. Trophic relations Potentially there is some competition with the bearded seal, Erignathus barbatus. There are no known predators. Interactions The current exploration for oil involves low flying aeroplanes, which have been shown to disturb the walrus. Population size From aerial surveys the following population estimates have been derived for the separate areas (see under Distribution): a few thousand about 10,000 over 3,000 over 140,000 An overall increase in population size has been noted recently.

Exploitation

Presently about 5% of the population of the Pacific walrus is taken annually (about 6,000 animals). The unretrieved kill is high: 30-50%of the animals killed. No harvest data are available for the other populations. The harvest of the walrus is regulated. Since 1972 there is only subsistence hunting allowed in Alaska for Eskimos, Indians and Aleutians, but no quota are set. In the Pacific region of the USSR, a quotum is set at 2,000 animals. In Canada the allowed kill is 7 animals per family per year, with a ban on export of hide and tusks. In Greenland, only Danish citizens are allowed to hunt the walrus in the Davis Strait and Baffin Bay. There has been no harvest in the Northeast Atlantic since 1952. In the Laptev Sea only natives and members of scientific expeditions are allowed to kill walruses. Threats to the population There have been investigations in the feasability of mollusk harvests in the Arctic. If mollusks would be exploited, this would mean harrassment and a reduction in food supply for the walrus. Arctic oil exploitation can create ecological problems and the traffic involved would disturb walruses.

References

Brenton, C. (1979)

Walrus. in: Mammals in the Seas, volume II: pinniped species summaries and report on sirenians. FAO Fisheries Series No. 5, Vol II, pp. 55-57

Fay, F.H. (1981)

Walrus, Odobenus rosmarus (Linnaeus, 1758). in: Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 1: The walrus, sea lions, fur seals and sea otter, pp. 1-23, Academic Press Inc., Ltd, London

King, J.E. (1983)

Seals of the world, 2nd edition. British Museum (Natural History), London and Oxford University Press, Oxford, 240pp.

Back to the Walrus Taxonomy Page

Back to the Main Page