The experts dissect a lion and a tiger. From the outside, the two look very different, but once their skins are removed, even the experts find it hard to tell them apart. Biologist Simon Watt comes face to face with a liger - a cross between a lion and a tiger - proof of the two species' similarity. One of the most characteristic features of these magnificent animals - something that distinguishes them from the small cats - is their ability to roar. The team delves into the lion's throat to find the voicebox and makes a discovery that helps explain the way the vocal apparatus works. Richard Dawkins explains the evolutionary arms race between predators and their prey in the struggle to survive. Finally, the experts try to find out why male lions have a distinctive mane.