David Attenborough tells the revealing story of this Caribbean island's exotic but vulnerable wildlife. A team of conservation champions are making it their mission to save the most precious species. We see how Puerto Rican parrots, manatees and turtles are now making a comeback.

The animal kingdom possesses a fearsome arsenal - a variety of extreme weapons used in epic battles to gore, stab, crush and batter. But are they more than just instruments of deadly force? For Professor Doug Emlen, it has been his lifetime's ambition to discover the secrets of nature's arms races, what triggers them and what they can teach us about the most formidable weapons on earth - our own.