In this episode we explore the anatomical secrets of some of the most fascinating animals on the planet.

Hugh Fearnley-Whittingstall is in the French Alps to find out how one man's understanding of an eagle's physical abilities could help him to unlock its potential and save it from extinction.

Conservationist Giles Clark is in Australia meeting a kangaroo that's more at home climbing in the trees than hopping through the outback. Giles is also in Kenya, where the latest research is revealing how hippos could be the life force of African river systems.

Zoologist Lucy Cooke is in Costa Rica to find out if the sloth's laziness is the key to its success, and in the UK she meets the scientists who have been investigating how one of the ocean's most effective predators, the sea lion, catches its prey in the dark.

Biologist Patrick Aryee discovers how a fox with supersensitive hearing can thrive in one of the harshest habitats on earth, and marine biologist Shanta Barley reveals the secrets of the platypus. Show less