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In page Harp seal:

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After abandonment, in the post-weaning phase, the pup becomes sedentary to conserve body fat. Within a few days, it sheds its white coat, reaching the "beater" stage.[4] This name comes from the sound a beater's tail makes as the seal learns to swim.[5] Pups begin to feed on at 4 weeks of age, but still draw on internal sources, relying first on stored energy in the body core rather than blubber.[3] During this time the ice begins to melt leaving them vulnerable to polar bears and other predators. This fast can reduce their weight up to 50%. As many as 30% of pups die during their first year, due in part to their early immobility on land.[4]