This is the story of two young animals forced to grow up fast. In Africa's savannah, a baby elephant shrew learns how speed is the secret to survival amongst the largest animals on Earth; and in America, a young grasshopper mouse confronts the Wild West's deadliest creatures to stake a claim of his own.
David Attenborough looks at the mammals that hunt insects. These creatures shared the planet with the dinosaurs, but when the giant reptiles disappeared they seized their chance to conquer new territory. David meets moles that swim through sand, a shrew that hunts underwater and another that sprints down polished running tracks so fast that most predators can't catch it.
This new age of discovery is revealing there is still so much to learn about the cat family. Using high-tech collars, Professor Alan Wilson has discovered it is not straight-line speed that is a cheetah's greatest weapon but their ability to break, change direction and accelerate. His research is rewriting what we understand about the fastest animal on land. This is also a crucial time for cat conservation - most are threatened, facing extreme habitat loss and conflict with humans. Yet there are many positive stories of cats bouncing back from the brink,
In this final episode Professor Brian Cox travels to Iceland, where the delicate splendour of a moonbow reveals the colours that paint our world, and he visits a volcano to explain why the sun shines. By exploring how sunlight transforms the plains of the Serengeti, drives the annual migration of humpback whales to the Caribbean and paints the moon red during a lunar eclipse, Brian reveals the colour signature of our life-supporting planet. Finally, at an observatory high in the Swiss Alps, he shows how these colours aren't simply beautiful, but that understanding how they're created is allowing us to search for other Earths far out in the cosmos.