One of the largest and most distinctive of all pinnipeds, the walrus is renowned for its enormous tusks, which can reach an incredible one metre in length. Although both sexes have the distinctively prolonged upper canines, the much larger male has tusks which are considerably longer and thicker than the female’s (2) (4) (5). The foreflippers are short and squarish like those of a sea lion, while the rear flippers resemble those of true seals, but compared with other pinnipeds, the walrus’ bulky body is much less streamlined (4) (5). The blunt muzzle of the walrus is also highly distinctive, as is the dense protrusion of whiskers on the upper lip (2) (4) (5). Walrus skin is remarkably thick and tough, an attribute that protects against injury from other walrus’ tusks, and from the rough rocks and sharp ice it lumbers over when hauling out (2) (6). Except on the flippers, walrus skin is also covered with short, coarse hair that grows sparser in adult males, particularly around the nearly bare neck and chest. In older bulls, this area is characteristically covered in lumps and nodules that are thicker than the surrounding skin, and protect the tissues underneath from the tusks of competitors (2) (4) (6). Skin colouration varies with activity, appearing pale grey when in cold water, due to reduced blood flow to the skin, but becoming characteristically darker reddish-brown when warm and dry (2) (4) (5) (6). Males also become paler with age, such that some older bulls almost look albinistic (4).
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