Walrus

Walrus from Blane Peruns TheSea.Org
Credit: KerryInLondon



The walrus is a massive, tusked marine mammal with flippers that lives in various icy regions surrounding the North Pole. They are easily recognized by the massive tusks that serve to immediately differentiate them from the otherwise similar-looking seals that they often share their habitat with. Despite being known for their size, they are not the largest pinnipeds. That honor belongs to the lesser-known elephant seal. The walrus is a keystone species in the arctic regions, where it serves a number of important ecological functions.

The walrus shares many traits with its seal and sea lion cousins, although its swimming manner stems more from seals than sea lions due to the emphasis on whole-body movement rather than its flippers. The walrus tusk is its most defining feature, and males with the largest tusks are often the most important in their social group. The walrus is unique among carnivores for its widespread eyes as most carnivorous creatures have eyes placed squarely on the front of the head. These are designed to make targeting and focusing on prey easy for the carnivore, a task that the walrus does not have need of on the seafloor.

Walruses are shallow divers that forage off the seafloor. They prefer not to dive as deep as other pinnipeds are known to, but rarely have to because of the widely varied and opportunistic diet that walruses have adopted. Walruses will eat shrimp, tube worms, crabs, soft corals, sea cucumbers, tunicates, and various mollusks off the seafloor during their foraging trips that can last up to half an hour. The walrus is known to prefer clams, using t’s powerful lips to break open shells and eat the meat inside.

Walruses rarely live past thirty years of age, and typically begin mating at fifteen years. Females will begin heat twice a year, at the end of summer and around the month of February. Interestingly, males are only fertile during the February mating season, and not the second, later summer one. During heat, males compete over the mating rights to ice-bound females who, upon choosing a mate, will jump off the ice and join them in the water. Gestation lasts up to sixteen months, and walrus calves are born during the annual spring migration, between the months of April and June.

Atlantic Walrus

The Atlantic walrus is one of the sub-species of the walrus. It is considerably smaller in size than its Pacific counterpart. The population in the Atlantic is also much smaller, with less than 20,000 estimated individual Walruses in the entire area.

Walruses are Pinnipeds, just like their cousins, the sea lions, fur seals, and true seals. With the scientific name Odobenus rosmarus, this animal is the only surviving member of the Odobenidae family. The species is divided into three subspecies; Odobenus rosmarus, which is the subject of this article, OR rosmarus divergens, the Pacific walrus and OR Laptev, a subspecies which is still subject to debate and living in the Laptev Sea within the Arctic Ocean.

The Atlantic walrus has a large body with a thick layer of blubber which serves as a thermal insulator in the cold waters of the Atlantic. This subspecies is significantly smaller than the Pacific walrus, with males averaging 900 kg and females 560 kg. The tusks are also smaller than in the Pacific populations, and the snout is more flattened. The snout has up to 700 bristles or vibrissae that act as detectors. With these, walruses can detect prey of even 1-2 mm long and wide.
Walruses can turn their hind flippers forward in order to walk on land, just as sea lions. However, they swim more like true seals, as they rely less on their flippers and more on sinuous movements. Walruses use their tusks to dig and maintain holes in the ice which serves as escape routes, to drag their bodies into the ice, for male dominance display, and for defense.

This subspecies inhabits the Canadian Arctic, as well as the coastal regions of Greenland and Svalbard. There are also some populations on the western shore of the Arctic part of the Russian Federation.

These walruses are opportunistic, and they prefer to hunt benthic species such as mollusks, crustaceans. They will also feed on tube worms, sea cucumbers and occasionally on birds or small mammals such as seals. Walruses are preyed upon by orcas, sharks, and polar bears, although they are not the main food source for those species, especially due to their large size and ability to fight back with their long tusks.

Females are known to delay implantation for up to three to four months in order to ensure warmer temperatures for the calves at birth. Females mate with dominant males and give birth to calves after a gestation period of 15 to 16 months. The Atlantic walrus can live for up to 30 years.

Pacific Walrus

The Pacific walrus, or Odobenus rosmarus divergens, is a subspecies of the walrus, or Odobenus rosmarus – a large marine mammal and the sole member of the Odobenidae family. It is related to sea lions and seals. The animal can grow to weigh 2,000 kg and has tusks that can exceed one meter in length.

The Pacific walrus has a bulky body with a small, round head. Sexual dimorphism is present, with males being considerably larger than females. Males are known to reach 2,000 kg, although they usually average between 800 and 1,700 kg. They can grow to be 2.2 to 3.6 meters long, with females being two-thirds of the size and weight of males.

Both males and females have long tusks, with males growing tusks that can be 1 meter long and weigh more than five kg. The Tusks are used for male display and fighting and by both males and females to drag themselves from water unto ice platforms. Tusks are used to maintain holes in the ice and they can also be used as weapons for defense against other animals. Besides the two species of elephant seals, the walrus subspecies in the Pacific is the largest pinniped. They have a large amount of blubber to keep them warm in low temperatures. The tusks are surrounded by bristles or vibrissae which are 30 cm long and can number from 400 to 700.

Just as the name suggests, this walrus subspecies lives in the Pacific. Populations can be found just north from the Bering Strait to the Chukchi Sea in the Arctic Ocean. They can also be seen on the eastern coast of Siberia and in the Beaufort Sea.

Walruses are opportunistic feeders and can consume a wide range of animals, from tube worms, crabs and shrimp to sea cucumbers and mollusks. They have also been found to occasionally prey on smaller seals as well as birds.

Males reach sexual maturity at the age of seven, but they usually start to reproduce only when they develop fully, at 15 years of age. Bulls fight for females and mate with several of them. Gestation lasts for 15 to 16 months. The calves can weigh up to 75 kg when they are born and they will be weaned after two years. The Pacific walrus can live for 20 to 30 years.

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