Walrus - Odobenus rosmarus

Taxonomy & Nomenclature

Scientific Name Odobenus rosmarus
Author (Linnaeus, 1758)
Taxonomic Rank Species
Taxonomic # 180639
Common Names English: Walrus
French: morse
Current Standing valid
Taxonomic Parents Kingdom: Animalia
  Phylum: Chordata
    Subphylum: Vertebrata
      Class: Mammalia
        Subclass: Theria
          Infraclass: Eutheria
            Order: Carnivora
              Suborder: Caniformia
                Family: Odobenidae
                  Genus: Odobenus
Taxonomic Children Subspecies: Odobenus rosmarus divergens
Subspecies: Odobenus rosmarus laptevi
Subspecies: Odobenus rosmarus rosmarus
Synonyms (since 1950)
Taxonomic data is courtesy of the Integrated Taxonomic Information System (ITIS)
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Physical Description / Field Identification

Walruses are very large, heavy-set pinnipeds. Males are longer and heavier than females. Adults have a short coarse pelage that becomes sparser in older males than in older females. The skin is thick, rough, and heavily marked with creases and folds. Older males have many lumps or nodules on the neck and chest, giving them a warty appearance, and most become virtually hairless. The neck, chest, and shoulders are massive, and the body tapers towards the hind flippers. The head, and especially the muzzle, are short, but very wide. The “bloodshot” eyes are small, somewhat protruding, and set far apart. The end of the muzzle is flattened and has large, fleshy, forward-facing mystacial pads sprouting several hundred short, stiff, whitish vibrissae. The nostrils are located on top of the muzzle. Walruses have no ear pinnae.

The foreflippers are relatively short and squarish resembling otariid foreflippers, with longer first digits and shorter subsequent digits, each with a very weakly developed claw. The hindflippers are phocid-like, with longer first and fifth digits, and strong expandable webbing between the digits, each with a small claw. The tail is attached to the body by a web of skin.

Walrus coloration varies with age and activity. Most walruses are yellowish brown. When walruses enter the cold water of their Arctic world, their coloration fades to a pale grayish ghostly hue, due to reduced blood flow to the skin, known as peripheral vaso-constriction. Conversely, when they come out of the water, vaso-dilation causes blood and color to return to the skin, and can, under warm conditions, cause the animals to appear pink to reddish, giving them the appearance of having a sunburn. Calves are darker with slate gray fur.

Males reach about 3.6 m and 880-1560 kg, females about 3 m and 580-1039 kg. Newborns are 1-1.4 m and weigh 33-85 kg.

The dental formula is: I 1/0, C 1/1, PC 3/3. Walruses are unique among pinnipeds, as the upper canine teeth develop into tusks that grow throughout life. The tusks are longer (up to 1 m) and thicker, with more grooves and fracture lines in males than in females, and one or both tusks can be partially, or entirely, broken off in adults of both sexes. Tusks also tend to be less curved and more divergent at the tips in males, and reach their greatest length in male Pacific walruses. Walrus calves are born without tusks, but they generally become visible below the lips at age 3-4 in the Pacific population.

Three subspecific populations are recognized: Atlantic, O. r. rosmarus, from the eastern Canadian Arctic, and Greenland east to Novaya Zemlya; Pacific, O. r. divergens, in the Bering Sea and adjacent Arctic Ocean, and; O. r. laptevi, from the Laptev sea, north of Siberia.

Can be Confused With

Walruses are unmistakable on land or ice and in most sightings at sea. At sea they should not be confused with any other species if more than the back is seen during a surface period.

Distribution

Arctic and Subarctic with a discontinuous circumpolar distribution. The Pacific subspecies is found in the Bering, and Chukchi Seas to the East Siberian Sea in the West and the Western Beaufort Sea in the East. The Atlantic subspecies occurs in numerous subpopulations from the Eastern Canadian Arctic to the Kara Sea. The Laptev walrus may not be distinct from the Pacific population, but is isolated in the Laptev Sea north of central Russia. All three subspecies of walrus are found in relatively shallow continental shelf areas, and rarely occur in deeper waters. They regularly haul-out on sea ice, sandy beaches, and rocky shores, to rest, molt and nurse their young.

Ecology and Behavior

Calves are born from mid-April to mid-June on sea ice. Courtship and mating has been little studied, because walruses mate in the harsh winter environment of the Arctic. It is believed that walruses are polygynous and that males may form a type of lek; they seem to establish small aquatic territories adjacent to females hauled-out on ice floes, where they vigorously vocalize and display. There is also some intense male-male fighting at this time.

Males have an unusual adaptation for producing a bell like sound when they are in the water. A pair of elastic pharyngeal pouches in the neck can be inflated with air and serve as resonance chambers for producing this unique sound. They also visibly enlarge the neck and provide floatation when a walrus is resting in the water. Walruses can walk and climb on land by using all four flippers to move the body in the manner of a sea lion or fur seal (family Otariidae). In the water they primarily rely on side-to-side sculling strokes of the rear flippers for swimming in the manner of a “true seal” (family Phocidae).

In the Pacific, walrus migration follows the seasonal advance and retreat of the sea ice. However, some walruses, particularly males, summer far from the sea ice, such as on Round Island, Alaska, using land based haul-out sites. Walruses also haul-out on shore, away from ice in years of reduced pack ice. Walruses are among the most gregarious of pinnipeds. Ashore and on sea ice they are regularly found in tightly huddled masses, often laying on top of each other; at sea they are often seen in large herds. Tusks are used for hauling-out, and holding onto ice floes, not for digging up food, as previously thought.

Feeding and Prey

Walruses feed on a wide variety of prey, chiefly benthic invertebrates. Some of the favorite foods are clams, worms, snails, shrimp, and slow-moving fish. Some “rogues” regularly prey on seals and small whales.

Threats and Status

All three walrus populations were severely depleted by episodic commercial hunting that was heaviest from the 18th through the mid 20th centuries. Native people of the Arctic have depended on walruses for food, hides, ivory, bones and more since first contact, and subsistence harvests continue today in many parts of the species’ range. Conflicts with fisheries are low, however industrial development, dispersal of pollutants, and human disturbance along with global warming all have the potential to have significant impacts on walrus populations in the future if they increase in intensity.

Links

References

Fay, F.H. 1982. Ecology and biology of the Pacific walrus, Odobenus rosmarus divergens Illiger. North American Fauna 74:1-279.

Fay, F.H. 1985. Odobenus rosmarus. Mammalian Species 238:1-7.

Fay, F.H., L.L. Eberhardt, B.P. Kelly, J.J. Burns and L.T. Quakenbush. 1997. Status of the Pacific walrus population, 1950-1989. Marine Mammal Science 13(4):537-565.

Kastelein, R. 2002. Walrus Odobenus rosmarus. Pp. 1294-1300 in W. F. Perrin, B. Wursig, and J. G. M. Thiewissen, eds. Encyclopedia of Marine Mammals. Academic Press.

Richard, P.R. and R.R. Campbell. 1988. Status of the Atlantic walrus, Odobenus rosmarus rosmarus in Canada. Canadian Field-Naturalist 102(2):337-350.

ITIS TSN180639
Status - ESA, U.S. FWS -
    -
Status - Red List, IUCN -
    VU (Global or one of the sub regions)
#records (spatial)3,373
#records (non-spatial)0
#datasets10
Year1971 - 2013
Latitude44.09 - 76.82
Longitude-171.96 - 14.65
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