Alaska: Earth's Frozen Kingdom

As spring lights up the land, Alaska faces one of the greatest transformations on earth. Temperatures soar, and as the sun's rays hit the snow and ice, water, light and warmth return. Alaska's transition to spring may look magical, but for those animals emerging from a long winter's sleep, it's a time of intense competition, as everything is in a rush to cash in on Alaska's riches.

No season brings more surprises than an Alaskan summer. It lures hummingbirds up from the tropics, exposes deserts in the Arctic and relies on parachuting firefighters to tackle forest fires in its vast wilderness. Summer is a narrow window of plenty, when the land is bathed in 24-hour sunlight - but in this land of extremes, you can have too much of a good thing.

Surviving the bone-chilling cold, deadly blizzards and darkness of an Alaskan winter takes courage, cunning and remarkable endurance. In the raw beauty of windswept mountain peaks, icy tundra and snowbound forests, this is the story of the tough and resourceful characters that face up to the ultimate challenges of this untameable land.