As newborns, polar bear cubs are about the same size as a loaf of bread and weigh about a pound (.37 kilograms). They have no teeth, their eyes are closed, and their fur is not thick. They need their mother's warmth and protection 24/7.

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Text by Ruth Musgrave

Photographs by Art Wolfe / Getty Images (above); Norbert Rosing / National Geographic Image Collection (den); Ken Graham / Accent Alaska (cub standing); Tom Mangelsen/ Nature Picture Library (bears swimming); Wayne R. Bilenduke / Polar Bear World, Inc. / Getty Images (mother with cub)

Video courtesy National Geographic Television