Frozen Planet

David Attenborough examines how the arrival of winter sparks a ruthless battle for survival in the polar regions, with temperatures plummeting to -70C, winds reaching 120mph and day-long darkness. As a blizzard rages, a polar bear treks into the Arctic mountains to give birth, while the entire world population of spectacled eider braves the weather in a giant ice hole. Wolves and bison engage in battle, but alliances are also made, and beneath the snow, voles try to dodge the attacks of great grey owls and weasels