The annual Arctic migration of caribou is the largest of its kind in Western Alaska. The western Arctic herd has the greatest numbers of the 25 Alaskan herds, with just under 500,000 caribou. Their migration is so large that at times the whole landscape appears to be on the move. On their journey, they face hardships and dangers which will take their toll, but the majority will survive for nature dictates that the caribou will always return. This programme profiles this extraordinary migration while examining their habits and social behavior.