Walrus

Scientific Classification

Common Name

walrus

Kingdom

Animalia

Phylum

Chordata

Class

Mammalia

Order

Pinnipedia

Family

Odobenidae

Genus Species

Odobenus rosmarus

Fast Facts

Description

Walruses are very distinctive having a large, robust, fusiform body that is usually reddish-brown in color. On their head region, walruses lack external ear flaps, have hundreds of short, vibrissae (whiskers), and both males and females possess large tusks. Like other pinnipeds, the fore and hind limbs of a walrus are modified into flippers. Although hair is present on the rest of the body, it is absent on the flippers. The foreflippers are short and square in shape with tiny claws on all digits, and the hind flippers are triangular in shape with larger claws on the three middle digits. On land, walruses are capable of rotating their hind flippers under their pelvic girdle to walk on all fours in a similar manner to sea lions.

Male: Adult males are slightly larger than females with longer and stouter tusks.

Size

The Pacific subspecies is larger than the Atlantic. Newborn calves are about 95 to 123 cm (3 to 4 ft) long.

Male: 2.7 to 3.6 m (9 to 12 ft)

Female: 2.3 to 3.1 m (7.5 to 10 ft)

Weight

Newborn claves weigh about 45 to 75 kg (99 to 156 lbs.)

Male: About 800 to 1,700 kg (1,764 to 3,748 lbs.)

Female: About 400 to 1,250 kg (882 to 2,756 lbs.)

Diet

Mainly bivalve mollusks such as clams; also other benthic invertebrates such as marine worms, snails, sea cucumbers, squids, and crabs. May occasionally prey upon fish such as polar cod and scavenge on seal carcasses. There are rare cases of very large, male walruses that habitually prey upon seals, especially ringed and bearded seals.

Gestation

15 to 16 months, including a period of delayed implantation

Estral Period

December through March

Nursing Duration

2 or more years (wean)

Sexual Maturity

Male: 8 to 10 years; successful reproduction probably not until about 15 years

Female: 5 to 6 years; successful reproduction at about 10 years

Life Span

Up to 40 years

Range

Arctic Sea, both Pacific and Atlantic (Bering, Laptev and Chukchi seas)

Habitat

In relatively shallow water, generally not more than 80 m (262 ft) deep. Hauls out on ice floes, pack ice and small rocky islands when ice is not present.

Population

Global: About 250,000

Regional: Pacific walrus population about 200,000

Status 

IUCN: Not listed
CITES: Appendix III
USFWS: Not listed

Fun Facts

1. Walruses spend about two-thirds of their lives in the water. Highly social in nature, huge herds of walruses haul out (leave the water to get on land) on sea ice to rest and bear their young. Most walruses live where the air temperature is about -15° to 5°C (5° to 41°F).
2. A thick layer of blubber insulates the walrus. Blubber may be up to 15 cm (6 in.) thick. During the winter, blubber may account for one-third of a walrus's total body mass. Blubber also streamlines the body and functions as an excess energy reserve.
3. To locate food, walruses use their vibrissae (whiskers). A walrus has about 400 to 700 vibrissae on its snout. Vibrissae are attached to muscles and are supplied with blood and nerves. A walrus moves its snout through bottom sediment to find food. Abrasion patterns of the tusks show that they are dragged through the sediment, but are not used to dig up prey. Walruses may also take in mouthfuls of water and squirt powerful jets at the sea floor, excavating burrowing invertebrates such as clams and may consume 3,000 to 6,000 clams within a single feeding.
4. The primary functions of the walruses' prominent tusks seem to be aiding in hauling out on ice and rocky shores and in establishing social dominance.
5. For more information about walrus, explore the Walrus InfoBook.

Ecology and Conservation

As for other marine mammals, the U.S. Marine Mammal Protection Act of 1972 protects walrus populations.

Bibliography

Byrum, J. Pinnipeds From Pole to Pole: Seals, Sea Lions and Walruses. SeaWorld Education Department Publication. San Diego. SeaWorld, Inc. 2000.

Jefferson, T.J. Leatherwood, S. and M.A. Webber. FAO Species Identification Guide. Marine Mammals of the World. Rome. FAO, 1993.

Nowak, Ronald M. (ed.). Walker's Mammals of the World. Vol. II. Baltimore: Johns Hopkins University Press, 1991.

Parker, S. (ed.). Grizmek's Encyclopedia of Mammals. Vol. IV. New York: McGraw-Hill Publishing Co., 1990.

Reeves, R. R., Stewart, B.S., Clapman, P.J., and J.A. Powell (Peter Folkens illustrator). National Audubon Society: Guide to Marine Mammals of the World. New York: Random House, 2002.

Reeves, R.R., Stewart, B.S. and S. Stephen. The Sierra Club Handbook of Seals and Sirenians. San Francisco: Sierra Club Books, 1992.

Riedman, M. The Pinnipeds: Seals, Sea Lions and Walruses. Berkeley and Los Angeles. University of California Press. 1990.

http://animaldiversity.ummz.umich.edu