The story starts in winter, when temperatures plunge as low as minus 40° F. Then as the temperature increases during spring and summer there’s a dramatic event at the core of this seasonal change – the thaw – when a torrent of meltwater cascades down the mountains and into rivers and lakes. How will the animals be affected?

A Yellowstone winter is brutal, and the grizzlies hunker down and hibernate. But this winter the temperatures have been erratic and some bears are emerging early. Finding food is a huge challenge, but our camera crews follow one male who’s lucky enough to hit the jackpot and find a bison carcass. But there’s pressure from the scavengers.

The population of Great Gray Owls is vulnerable in Yellowstone, and this winter they’re suffering as their prey hides under an icy layer of snow that proves almost impossible to break through. Cameraman Jeff Hogan follows them to see if the lack of food will affect their ability to raise a family in the Spring. And even when there are chicks born, can they all survive?

Down on the Snake River infrared cameras spy on beavers fighting inside their lodge. Plus Kirk dons a dry suit and heads underwater to admire the engineering skills of these rodents. Massive boulders and branches are there to strengthen their dams, but will they be enough to withstand the thaw?

Top wolf biologist Doug Smith outlines why he’s concerned about the number one predator. With a winter that’s had less snow than usual, both the wolves and their prey are starving. Charlie Hamilton James in on the trail to understand how they’re staying alive.

Throughout the year, bear expert Casey Anderson follows the grizzlies. But there are two young orphans, and can they survive without mum to teach and protect them?