Majestic creatures of the far north, Polar bears are the world's largest terrestrial carnivore. They are excellent swimmers and spend most of their life in or around water. As the southern edge of the Arctic ice cap melts, in the summer, Polar bears follow the retreating sea ice. As a result of global warming, however, sea ice in the Polar bear's hunting grounds is melting earlier and forming later each year. If present trends continue, this "king of the great white north" could be extinct by the end of this century.