The Last Saber-Toothed Seal

Walrus (Odobenus rosmarus) in Nunavut,Canada (photo by Mark Carwardine)

Today we feature one of everyone’s favorite animals–the great toothwalkers of the northern oceans, the mighty walruses (Odobenus rosmarus).  Adult Pacific male walruses can weigh more than 2,000 kg (4,400 pounds) and grow to lengths exceeding 13 feet.  The huge pinnipeds live in vast colonies ringed around the Arctic Ocean.  Females separate themselves from the fractious males in order to protect their calves from the squabbling and dueling of the bulls.  The tusks (which can grow to 1 m (3 ft 3 in) in length) are also used by both genders to leverage their great weight out of the water—hence the name “toothwalker.” The word walrus comes from the Old Norse word “hrossvalr” which means horsewhale.

(photo by Max Smith)

The distinctive face of the walrus is a mass of large coarse bristles properly known as vibrissae.  Like the barbells of a catfish, these vibrissae are extremely sensitive tactile organs which help the walrus find shellfish on the dark and turbid ocean bottom.  Walruses are capable of diving deep to find the invertebrates they like to eat.  Scientists have recorded dives of 113 meters (371 feet) which lasted for about 25 minutes.  Once the walruses have located a food source to their liking, they dislodge their prey with jets of water and then suction up the creatures.  Apparently they are most partial to bivalve mollusks, snails, sea cucumbers, and crabs, but in extreme circumstances they can hunt large fish or even smaller seals.

Walruses can sleep in the water, their heads supported by an inflatable pouch which allows them to bob comfortably in the choppy near-freezing water.  Additionally they change color with the temperature—their surface skin can be pink, as blood rushes near to the surface when they are hot, or they can turn grey brown when cold.

Walrus colony. Source (U.S. Fish and Wildlife Service)

All pinnipeds, including walruses, are in the order Carnivora where they seem to most closely share a common ancestor with bears back in the Oligocene. Walruses are the only species in the only genus of the family Odobenidae.  Once the Odobenidae were a sprawling family with at least twenty species spread across three several subfamilies (the Imagotariinae, Dusignathinae and Odobeninae), but something went wrong and walruses are all that’s left of the saber-toothed seals.

Polar bear attacking walruses (from the BBC's series "Planet Earth")

Walruses’ only natural predators are polar bears and killer whales, but even the world’s largest land predator and the most formidable ocean predator find adult walruses intimidating.  Except in extraordinary circumstances the huge predators only hunt calves or weakened walruses. Predictably, humans are the walruses’ main problem.  In the 18^th, 19^th, and 20^th century immense numbers of walruses were killed for blubber, skin, meat, and ivory.  Today this commercial exploitation has ended and worldwide populations have rebounded somewhat–though certain geographic areas remain depopulated.

Perhaps because they move ponderously on land and because their whiskers suggest comic uncles, some people underestimate walruses. I have been fortunate enough to see a young adult walrus in captivity (he was orphaned as a pup and would have died if not taken in by an aquarium) and it is a mistake to underestimate these animals.  The walrus (whose name was Ayveq) was as large as a midsized truck, yet he could move with shark-like speed but ballet-like grace in the water.  Bull walruses come into maturity at the age of 7, but they don’t usually get to mate with cows until they are 15 or so and have bested many competitors in savage sword duels with their tusks. Ayveq had access to a harem of walrus cows from a much younger age, and his comic attempts to understand himself and his relation to the females was a source of much surprised astonishment among aquarium-goers.  As a peripheral point, I neglected to mention that male walruses have a uniquely large baculum which can measure up to 63 cm (25 inches)—larger than that of any other land mammal.  The apparatus supported by this bone is similarly oversized.

A tame picture of Ayveq the Walrus (he liked to mush his face against the glass)

Ayveq could produce a remarkable series of shrieks, grunts, whistles, bellows—apparently communication is important in the teaming masses of walrus colonies. Whether drinking herring through a straw, mugging for a crowd, or using his back flippers to amuse himself, Ayveq was always remarkable. His death saddened me considerably and I could not write about walruses without mentioning his extravagant personality.  Knowing Ayveq also left me convinced that walruses might be perverts but they are also highly intelligent and gregarious beings.  This conviction is born out by the painstaking work of biologists and zoologists who are just beginning to recognize how complicated walrus society is.  It is no wonder, that so many poets, artists, and musicians have referenced the remarkable tusked creatures.

The Walrus and the Carpenter from Alice in Wonderland (Walt Disney)

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