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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 18th, 19th, and 20th 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)

From time to time, Ferrebeeekeeper indulges in a theme week.  Last Halloween featured Greek Monster Week, which highlighted the mythical spawn of Echidna, the great serpent mother of classical mythology.  Other theme weeks have included Tree Week and Small Furry Animals Week (which described the groundhog, the pika, the hyrax, the rabbit, and the wombat).  In order to combat malaise in the world construction markets, Ferrebeekeeper now presents Builders Week, five posts dedicated to great builders and the edifices they have created.  To start off the week, this post is dedicated to the beaver, the most accomplished and tireless builder of the animal kingdom–save perhaps for corals, termites, and humans.  Not only is the busy building beaver a keystone species to ecosystems around the Northern hemisphere, the furry rodent holds a key place in American history.

Eurasian Beavers (Castor fiber) photo by zooadmin

There are two species of beaver, the North American beaver (Castor Canadensis) and the Eurasian beaver (Castor fiber).  Although similar in appearance and habit, the two species are not genetically compatible and, when mated, do not produce living offspring.  Like the other giant rodents (capybara, nutrias, etc) beavers are semi aquatic and spend nearly as much time in the water as on land. In order to get around on land and water, beavers have webbed clawed feet and a flat, hairless paddle-like tail.  Their ears and nostrils clamp shut under water and a special membrane snaps over their eyes.  In order to keep warm in harsh northern winters, beavers have a layer of subcutaneous fat as well as a dense coat which they waterproof with oily castoreum (produced from a scent gland).  To round out their special features, beavers possess formidable upper and lower incisors with which they gnaw down trees. Adult beavers can weigh up to 30 Kilograms (about 60 pounds) and attain lengths of 1.3 meters (about 4 feet).

North American Beaver (Castor canadensis)

Beavers are intelligent animals which form close family bonds. According to the website Beaver: Wetlands and Wildlife:

Wildlife rehabilitators find beavers to be gentle, reasoning beings who enjoy playing practical jokes…. Beavers mate for life during their third year. Both parents care for the kits (usually one to four) that are born in the spring. The youngsters normally stay with their parents for two years, and the yearlings become babysitters for the new litter. After weaning, their favorite foods include water lily tubers, apples and the leaves and green bark (cambium) from aspen and other fast-growing trees.

Above all, the beaver is a masterful builder capable of cutting down large trees and moving them into place to serve as the foundation of a dam.  Reinforced with mud, and “planted” with living green shoots (which grow into the structures and thus add stability), beaver dams curve backwards against the current and are capable of holding immense volumes of water. Not only do beavers fell trees and create timberworks and earthworks, the creatures also excavate canals to provide a quick escape into the artificial lakes produced by their dam building. Within these lakes the beavers build lodges as escape shelters and winter homes.

Cross-section of a Beaver Lodge (DEA Picture Library/De Agostini Picture Library)

Such lodges can only be entered through hidden underwater entrances.  Crafted in sprawling mounds from logs, branches, and mud, the structures contain rooms for dying off and rooms for habitation.  Before winter the beavers coat their lodges with mud which freezes into a hard coat which makes the structures impervious to bears and wolverines. Beavers harvest tender shoots from their favorite softwoods and embed them deep in the mud of the coldest deepest part of their lakes.  In winter when the top of the lake is frozen, the animals can dive down and retrieve food from their underwater refrigerator.

The Largest Known Beaver Dam Photographed from Space

Beavers are ambitious in their work. To date the largest beaver dam discovered was over 850 meters in length (2,790 feet)–more than twice the width of Hoover Dam. Located in the forests of Alberta in Canada the huge dam was spotted from space via Google Earth.

The flooded lands formed by these dams provide a habitat for waterfowl, turtles, frogs, and other aquatic creatures (as well as protected nurseries for salmon fry). Additionally the dams alleviate flooding, allow the water table to recharge, and act as filters which soak up nitrogen and chemicals.  Some writers have (poetically?) described beaver dams and related lakes as the kidneys of a watershed. Since beaver dams are depositional environments, they silt up into rich bottom land when abandoned by their builders. This process is vital to forests and rivers in North America and Europe, where soft quick growing trees have evolved to deal with beavers’ appetite and industry. However beavers have caused disastrous flooding and environmental mayhem when furriers introduced them to areas (like Tierra del Fuega) where trees do not coppice.

The Fur Trade

Furriers have a long dark history with the beaver. Eurasian beavers were over-harvested to the point of near extinction by medieval trappers for their lustrous coats.  When the New World was being conquered and colonized by European nations, the valuable fur of North American beavers was one of the first economic incentives for exploration.  Trappers, traders, and runners-of-the-woods traveled deep into North America for the pelts of all manner of creatures: but they sought beaver hides foremost.  The dense fur was ideal for making the fashionable flamboyant hats of the seventeenth and eighteenth centuries (additionally beavers were classified as fish by the Catholic church and their flesh had special allure for hungry devout French trappers during Friday fasts). Competition between French and English fur traders for the pelts from the territory between the Alleghany Mountains and the Mississippi combined with long brewing national conflict to start the French and Indian War which in turn determined the course of civilization in North America.

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