Over 100,000 caribou face starving bears and wolves, deadly frozen rivers and rugged mountains, as they undertake the world’s longest land migration - 3,000 miles through the frozen Arctic wilderness of Canada and Alaska. Joining them are a team of scientist and wildlife filmmakers who, with the help of satellite tracking collars, will attempt to follow the caribou on foot as they undertake the most challenging part of their migration.

Thousands of zebra face lions, hunting dogs, drought and starvation as they undertake the world’s most newly discovered migration. Braving one of Botswana’s most brutal wildernesses, they make Africa’s longest land mammal migration to the rich grasslands of Nxai Pan National Park, 155 miles to the south.