Walrus | Oceana
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Marine Mammals

Walrus

Odobenus rosmarus

Distribution

The Arctic Ocean and adjacent seas

Ecosystem/Habitat

Rests on beaches and the ice surface; Feeds on soft bottoms

Feeding Habits

Foraging predator

Conservation Status

Unknown

Taxonomy

Order Pinnipedia (seals, sea lions, and relatives), Family Odobenidae (walruses)

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The walrus is one of the most charismatic species of the Arctic Ocean and adjacent seas, noted for the very large size of the ivory tusks. Throughout evolutionary history, there have been many similar species, but the walrus is the only survivor in the family. True seals and eared seals are the walrus’s closest relatives; collectively all of these groups are known as pinnipeds. The walrus is one of the largest pinnipeds, with males reaching weights of as much as 4400 pounds (2000 kg).

The walrus’s tusks are actually greatly elongated canine teeth.  Both males and females have tusks, with the males’ being much longer.  The largest tusks can reach lengths over three feet (one meter) long.  They are used to fight to establish dominance hierarchies, to avoid predation, and to haul out on the ice surface to rest.  They may also be used to maintain breathing holes in the ice so this species can feed under the ice during the winter.  Walruses are foraging predators that feed on a variety of bottom invertebrates, including shellfish, worms, crabs, etc. and perhaps some fishes.  They may also scavenge carcasses of large marine mammals.  As they are very large, walruses have few natural predators, but polar bears and killer whales are known to occasionally attack them.

There are two subspecies of walruses, divided by geography.  One subspecies lives in the north Pacific Ocean and the Arctic above the Pacific; the other lives in the north Atlantic Ocean and the Arctic above the Atlantic.  The Pacific subspecies is somewhat larger than the Atlantic subspecies and also more migratory in nature.  While Atlantic walruses utilize ice-free beaches during the summer while they wait for sea ice to return, Pacific walruses follow the ice edge north during the summer and south during the winter.

Like in many pinnipeds, male walruses are territorial.  Interestingly, mating takes place in the water rather than on beaches or on the ice surface like in other species, so males have aquatic (rather than terrestrial) territories during mating season.  Dominant males mate with several females that live within their territory and defend their females from other males.

The conservation status of the walrus is currently unknown.  During the 18th and 19th centuries, commercial hunting resulted in substantial reductions in the overall number of walruses but subsequent protection throughout much of their range likely allowed the species’ numbers to rebound.  However, as their life cycle heavily depends on sea ice, global warming and associated ice loss continues to be a threat for this and other Arctic species.  

 

Additional Resources:

http://www.iucnredlist.org/details/15106/0

 

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