With the arrival of spring, days grow longer and temperatures rise. But spring in Alaska is short. Animals have two months to feed, and start a family, while avoiding predators. Spring is also the time that millions of birds return to Alaska.

Summer has arrived in Alaska. Free of ice, rivers and streams can flow again. This sets the scene for one of the world's greatest migrations, the Alaskan salmon run.

Young animals prepare for their first winter away from their parents, humpback whales return to Alaska's rich feeding grounds and salmon return to spawn in the rivers where they were hatched. But the returning salmon have to negotiate a path past hungry brown bears fattening themselves before they hibernate.