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Weddell seals are underwater, making a breathing hole in the ice. As they have especially wide gapes and long canines and incisors, they can scrape away the ice that is constantly forming and threatening to close their breathing holes. But their teeth are not impervious to this wear and tear and are gradually worn down until the seal can no longer eat. As a consequence, Weddells die at around 20 years of age, half the age of other Antarctic seals. A male Weddell seal will defend his underwater territory and mate with all the females that use his breathing holes. This is an effective way of collecting a harem as females need to shelter below the ice during the extremes of the winter weather. Above the ice it may seem that there could not be a harsher existence, but the environment is actually comparatively constant and the seals are used to it. They are protected by a coat of dense hair and insulated by blubber immediately beneath the skin. In fact, Weddells do far better than other seals. If the pup is fattened sufficiently before weaning, 95 per cent of Weddell pups will survive.