How Big Is a Walrus? Weight of Bulls, Cows and Calves

How much does a walrus weigh?

Walrus weights vary with sex, subspecies, age and season. Males are much heavier than females, which weigh about two-thirds as much on average, and Pacific walruses are about 10–20% heavier than Atlantic walruses.

Adult walruses measure about 2.2–3.6 m (7–12 ft) from nose to tail. Bulls reach the top of that range, while cows are usually up to about 3 m (10 ft) long.

The Alaska Department of Fish and Game describes Pacific bulls as up to about 12 feet long and up to 2 tons in weight, while adult females can weigh more than a ton. Some Atlantic females weigh as little as about 400 kg (880 lb).

Bulls versus cows

The difference between the sexes, called sexual dimorphism, is clear at a glance. Adult bulls are bigger and bulkier, with a broader muzzle, longer and thicker tusks, and a massive neck and chest. Their skin is up to about 10 cm (4 in) thick on the neck and shoulders and covered in rounded lumps called bosses, which help protect them during fights.

Size matters for males because they compete for females during the winter breeding season. Bigger bulls with bigger tusks usually win, so males keep growing for longer. Females reach full size at about 10–12 years old, while males do not reach full size until about 15–16 years. The same contest explains the tusks, as described in What are walrus tusks for?

Blubber, skin and seasonal weight

A large part of a walrus’s weight is fat and skin. The blubber layer can be up to about 15 cm (6 in) thick. It insulates the walrus in water that is often near freezing, helps it float, and stores energy for lean times.

That stored energy matters because walrus weights change through the year. Breeding males eat very little during the winter mating season and lose weight, then make it up later. Pregnant and nursing females need extra food, and walruses that spend long periods resting on land between feeding trips also burn fat. As a result, the same walrus can weigh considerably more at one time of year than at another.

How big are walrus calves?

Walrus calves are already large at birth, about 45–75 kg (100–165 lb) and roughly 1–1.4 m (3.3–4.6 ft) long. A calf can swim almost immediately and nurses for more than a year.

Calves grow steadily on their mother’s milk and later on clams and other seafloor prey. According to the Alaska Department of Fish and Game, young Pacific walruses weigh about 340 kg (750 lb) by the time they become independent at around two years old.

The biggest walrus on record

The walrus has produced some famous size claims. Early 20th-century reports describe bulls whose skins alone weighed about 450–500 kg (1,000–1,100 lb), and because skin makes up roughly a fifth of a walrus’s weight, those animals were estimated at 2,300 kg (5,000 lb) or more.

A 2015 review of marine megafauna sizes by McClain and colleagues found these old records hard to verify. The heaviest reliably measured walrus in their data was a male of about 1,883 kg (4,151 lb) and 3.8 m (12.5 ft) long, and the longest reliable measurement was about 3.95 m (13 ft). Bulls of around 2,000 kg (4,400 lb) are therefore the realistic upper limit.

How does a walrus compare with other big animals?

Among pinnipeds, only the elephant seals are bigger. Male southern elephant seals can reach about 3,700 kg (8,200 lb) and 5.8 m (19 ft), and male northern elephant seals usually weigh 1,500–2,300 kg (3,300–5,100 lb), as described in How big is an elephant seal?

A big walrus bull can outweigh two or three adult male polar bears. The polar bear is the walrus’s main predator on the ice, but it usually goes after calves rather than healthy adults. For the giants of the oceans and land, see the largest animals in the world.

Why are walruses so big?

A large body helps in the Arctic in several ways. Big animals lose heat more slowly, because they have less skin surface for their volume. A thick store of blubber lets walruses survive periods when they feed little, such as during the breeding season or long stays on shore. Size also protects adults from predators, and in males it decides who wins the competition for mates.