The walrus, Odobensus rosmarus, is a close relative of seals,
but has two separate hind legs while those of seals are fused. Males reach
4 m in length and weigh up to 1200 kg, while females rarely exceed half
this weight. Walrus are best known for their unique tusks, the only ones
of their kind among marine mammals. They are actually two elongated canine
teeth. Their name, Odobensus, means "tooth walker", referring
to their behaviour of dragging themselves along the ice using their tusks.
The species name, rosmarus, is derived from the Norwegian word
for "whale horse".
In summer, walrus herds often bask on small islands or ice floes, and at such times they turn pink as their blood vessels dilate to aid in heat dissipation. During the winter breeding season, animals move to areas of open water and females form small bands of approximately twelve individuals. When feeding, walruses dive up to 100 m in search of clams, their primary food.
Walrus calves are born in May and usually stay with their mothers for two years. Thus, females breed only every second or third year. Males reach sexual maturity much later in life than females because they need to reach a larger size before they can compete in battles for access to females. Dominance among males is established by physical combat during the breeding season, and the duels are fought with their tusks. The victor gains control of a harem, which contains up to 100 breeding females.