Deep inside a volcanic crater in East Africa, lioness Malkia has reigned supreme for 16 years. Now though, her status is under threat as inbreeding and fierce rivalry threaten to tear the pride apart.

In Norway's brief spring, polar bear Binne races to double her weight before the arctic weather returns.

For the bears of Katmai National Park, spring marks the end of hibernation and the beginning of the annual contest for food and mating rites.