Undercover cameras reveal how living in the snow tests animals to their limit. In New Zealand, cameras follow a group of kea parrots, revealing how friendship is at the heart of the lives of these sociable and highly intelligent birds. Elsewhere, in the North Pole, cameras get up close to play-fighting polar bears, while on the other side of the planet at the South Pole, footage reveals the parental devotion that emperor penguins have as they try to secure the survival of their offspring and face some of the harshest conditions on Earth