The Frozen North, where wolves and polar bears vie for food, hares outsmart lynx and walrus sing on rocky shores. As summer arrives, grouse perform mating dances, caribou migrate vast distances and salmon race upstream to survive.

The Andes, Earth's longest mountain range. Baby bears make treacherous descents, rare hummingbirds compete for mates, frogs freeze and revive, and lizards battle for territory - all in a land of extremes, from glaciers to deserts.