Odobenus rosmarus
The last member of a family that once held many, and the strangest face in the Arctic.
There are three living families of pinniped. The true seals, family Phocidae, hold eighteen species in this archive. The eared seals, family Otariidae, hold fifteen sea lions and fur seals. The walrus is the third family, Odobenidae, and it is the only living member of it. Everything else in that family is a fossil.
You can see why it does not fit either of the others. Like a true seal, it has no external ear flaps at all, only small openings on the sides of the head. But like an eared seal, it can rotate its hind flippers forward underneath the pelvis and walk on all fours, and it moves fast in short bursts when it wants to. A true seal cannot do that. It humps along on its belly because its hind flippers trail permanently behind. So the walrus takes one trait from each side and belongs to neither.
It is a serious animal by size. Pacific males reach up to 3.6 m and roughly 880 to 1,557 kg, which makes this the third largest pinniped on Earth, behind only the two elephant seals. The heaviest reliably measured walrus was a 3.8 m male weighing 1,883 kg. Older claims of 2,000 to 2,300 kg animals were re-examined in a 2015 review and found to be unverifiable.
A walrus hunts in the dark. It feeds on the muddy floor of shallow Arctic seas, often under ice, where there is little light and the food is buried out of sight. It finds its meals almost entirely by touch.
The tool is the moustache. Those 400 to 700 bristles, arranged in 13 to 15 neat rows on a thick fleshy muzzle pad, are not decorative hairs. Each sits in a follicle wrapped in muscle and packed with nerves and blood vessels, and the animal steers them actively rather than letting them trail. In experiments, walruses using only their whiskers could tell apart shapes just 3 millimetres thick and 2 millimetres wide. That is tactile discrimination comparable to a human fingertip, mounted on the front of an animal weighing a tonne.
For a sense of how much nerve tissue this takes, look at the bearded seal, another Arctic bottom feeder built for the same job. Each of its individual whisker follicles averages 1,314 myelinated nerve fibres, among the highest counts recorded in any mammal. A walrus sweeping its muzzle across the seabed is running a dense sensory array over the mud, feeling for the outline of buried clams.
Once the whiskers find a clam, the walrus has to get it out of the sediment and out of its shell. It does neither the way most people assume.
To excavate, it blows. A walrus directs jets of water out of its mouth at the seafloor and fans with its front flippers, blasting the mud away. This has been filmed and measured, and it can clear sediment to a depth of around 30 cm, leaving long furrows across the seabed. To extract, it sucks. The walrus clamps its lips around the exposed clam and pulls its thick, piston like tongue sharply backwards, generating a vacuum that yanks the animal clean out of its shell. Measured suction pressures reach about minus 88 kilopascals in air and minus 119 underwater. Captive walruses at a German zoo once used this to suck a 2.3 kg metal plug out of the floor of their pool. The empty shells drop back to the bottom.
That habit produced the best number on this page. Divers following wild Atlantic walruses in northeast Greenland collected the freshly emptied shells after each dive and counted them: an average of 53.2 bivalves per dive, ranging from 34 to 89. From that they estimated a 1,200 kg bull eats about 57 kg of clam flesh and shell a day, roughly 4.7 percent of its body weight. You will very likely run into a claim that a walrus eats 3,000 to 6,000 clams in a single feeding. That figure cannot be traced to any primary source and should not be repeated. The verified number is the 53 per dive above, and the IUCN's own careful wording for a long feeding bout is simply that thousands of clams can be consumed in a single meal.
The most common walrus fact in circulation is wrong. Walruses do not dig for clams with their tusks. The Alaska Department of Fish and Game states it flatly, and wear pattern analysis backs it up: the tusks are dragged through the sediment while the upper edge of the snout does the digging, helped by those jets of water. If someone tells you a walrus ploughs the seabed with its tusks, they have the tool and the job mixed up.
What the tusks actually are is teeth. They are the upper canines, elongated and growing throughout life, reaching up to a metre long and 5 kg in a large bull. Both sexes have them. Males' tusks are longer, straighter and stouter, females' shorter and more curved, and the rest of the dentition is flat and reduced.
They do three jobs. They are weapons and status symbols, used in fights and threat displays between males, which is why bulls are so heavily scarred. They keep breathing holes open in the ice. And they are climbing hooks: a walrus in the water hooks its tusks over the edge of an ice floe and hauls its enormous body out of the sea. That last one is baked into the name. The genus Odobenus comes from Greek words meaning tooth and walk, tooth walker, because early observers watched them pull themselves out of the water on their teeth.
Walruses need three things in the same place: a wide area of shallow water with good clam beds, open water over those beds, and somewhere to rest nearby. Their preferred resting platform is sea ice, which is essentially a drifting raft parked directly over the dinner table.
That arrangement is coming apart. When summer sea ice retreats off the continental shelf and out over water too deep to feed in, the ice stops being useful and walruses are forced ashore. Since 2007, tens of thousands of Pacific walruses have hauled out on beaches along the Chukchi Sea coast of Alaska and Russia. Land haulouts are dangerous because walruses panic. Aircraft, boats, hunters, dogs, polar bears and tourists can all set off a stampede to the water, and calves and yearlings get crushed. More than 2,600 carcasses were found along the Russian Chukchi coast in autumn 2007, most killed by trampling.
This is why the IUCN listing is unusual, and why it is worth explaining. Walrus is listed as Vulnerable on the basis of projected future habitat loss, not on any measured population crash. The 2016 assessment concludes only that abundance is likely more than 225,000 and that the trend is unknown. The best Pacific figure, 257,193 animals, comes from a genetic mark and recapture study and carries a credible interval running all the way from 171,138 to 366,366. The US Fish and Wildlife Service states outright that because that interval overlaps with earlier estimates, the current trend for the stock is unknown. Anyone quoting a confident walrus population trend, up or down, is going beyond the evidence. Arctic peoples have hunted walrus for thousands of years and legal subsistence hunting continues in Alaska, Chukotka, Canada and Greenland, with reported harvests falling from an average of 10,970 a year in the 1980s to 4,327 in the 2010s.
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