A thousand elephants, from magnificent bulls to vulnerable orphans, come together in a crucial annual gathering in northern Kenya, whilst facing deadly threats from both predators and poachers.
A hundred thousand caribou must face hungry 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.
Thousands of zebra face lions, hunting dogs, drought and starvation as they undertake the world's most recently discovered migration. Braving one of Botswana's most brutal wildernesses, they make Africa's longest land migration to reach the rich grasslands of Nxai Pan National Park.
