Life at the Limits

Orangutans forage early in the day inside the rainforests of Sumatra - before the heat becomes unbearable. When the sun reaches its zenith all activity stops and the primates retreat to their shady nests below the canopy to wait out the heat. Winter in northern Yukon Territory - a frozen white landscape stretches into the distance. But high up on the Arctic Circle, one unique river still flows - because it's fed by an underground spring. Chum salmon exploit this anomaly. They travel thousands of kilometres to spawn here - later than anywhere else. And grizzlies ...