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Pinnipednesday - Odobenus rosmarus Edition

We're on the home stretch with this series, folks!

The Walrus (Odobenus rosmarus) are the third largest pinnipeds in the world, after both the Northern and Southern Elephant Seals, and can be found in the arctic and subarctic waters of the Northern Hemisphere. They are the only extant species in the Odobenus genus. They are distinguished primarily by their long tusks, which are elongated tusks used to dig and maintain air holes in the ice, as well as in dominance displays by the adult males.


The size and weight of Walruses depends primarily on the subspecies. There are currently three recognized subspecies:

  • Odobenus rosmarus rosmarus (northern Atlantic Ocean)
  • Odobenus rosmarus divergens (northern Pacific Ocean)
  • Odobenus rosmarus laptevi (Arctic Ocean, specifically the Laptev Sea)

The largest Walruses are typically O. r. divergens, the Pacific Walruses. Some of the adult males have weighed in at 4,4000 pounds (2,000 kg), but most of the more typical males only get up to 3,700 pounds (1,700 kg). Atlantic Walruses have about 10-20% less body mass than Pacific Walruses. Walruses can grow up to almost 12 feet (3.6 meters) in body length. Adult females are smaller than the males.


Compared to other pinnipeds, the Walrus appears to have bare skin instead of a fur coat. This is generally true, although they are covered with sparse hair, with their most apparent hair being their vibrissae. Their skin, however, is remarkable, and makes up about 20% of their entire body mass. The layer of blubber beneath the skin's surface can be up to 6 inches (15 cm) thick. And yes, like everyone has heard, the males do have the largest penis bone both relative to their body size, and in absolute size. Walruses have a diverse diet, and will feed on mollusks, shrimp, sea cucumbers, and soft corals. They tend to graze along the sea floor, and don't typically dive very deep for their food.


The mating season of Walruses typically takes place from January to April, with the males gathering with the females on the pack ice and asserting dominance over each other with threat displays - sometimes actual fights. Copulation actually takes place in the water, and though Walruses practice delayed implantation like most other pinnipeds, the total gestation period can be up to 16 months. Since females do not ovulate until their pups are weaned, they will only give birth once every two years, instead of annually. Pups are completely weaned after a year, but can stay with their mothers for up to five years.


Walruses are formidable animals, and as such only have two major predators, which are orcas and polar bears. In both predators' cases, adult Walruses are more trouble than they're worth, and it is usually the young Walruses that are taken, if at all. Walruses have also been a traditional staple for the indigenous peoples of the Arctic, but they were heavily hunted by European and American commercial hunters during the 18th and 19th centuries. This nearly led to the Atlantic subspecies, O. r. rosmarus, being completely extirpated. Today, hunting is regulated and Walruses are threatened more by climate change.


Source for all images used in this post.

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