Patrick Aryee follows the grizzly bears, who are taking a risk with the weather by leaving their winter dens early. Hungry wolves are struggling to bring down their elk prey in the unusually shallow snow. And for great grey owls it's the iciness of the snow that is hampering their hunts. Yellowstone’s winter is always one of the most brutal on the planet. But 2016 saw weather records broken, and the wildlife was forced to adapt to survive. Kate Humble gets to grips with the science behind this remarkable season.