A team of scientists follow elephants in northern Kenya, as they cope with daily challenges.

100,000 caribou face starving bears and wolves, deadly frozen rivers and rugged mountains, as they undertake the world's longest land migration - 5,000 miles through the frozen Arctic wilderness of Canada and Alaska.

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 migration.