The massive Arctic snow melt triggers a chain reaction causing the dramatic arrival of millions of animals that now must share one habitat. For a caribou and her calf, it will be a struggle of life and death.

In the rain forest of British Columbia, Canada, the survival of the last big North American carnivores depends on the yearly salmon run. As the rivers teem with salmon, the bears and wolves are drawn together in a deadly conflict.

The arrival of the annual rains in the parched grassland of East Africa's famous Serengeti plain brings greenery and fresh grass, drawing in a huge concentration of large animals. Now they must survive the arena of carnivores.

As winter arrives along South Africa's east coast, cooling inshore waters draw billions of sardines northward to feed on the plankton-rich soup. This attracts an awe-inspiring cast of ocean predators that feast on the sardines.

The Okavango River floods a sun-baked desert in Botswana, drawing in an enormous amount of wildlife, including predators like crocodiles, wild dogs and lions. It's a crucial moment for an elephant family trying to make it through.

When spring falls on the Pacific Northwest coast of America, it sets off a race for survival that calls all predators to the starting block. A young humpback, faced with the journey across the Pacific to feed, tries to survive.