The Siamese Fighting Fish is so aggressive it will fight its own reflection until it is exhausted. Recent research shows that the fighting behaviour varies and depends on the personality of the fish! Male kangaroos were once pitted against humans in the boxing ring – the most impressive male kangaroos are solid blocks of muscle with a kick that can kill. Why do they fight and what skills must a winner have?

David Attenborough investigates two shells that have proved to be winners in evolution: the bird's shell and the hard shell of the tortoise. The ostrich egg is so strong it's possible for a person to stand on it without it breaking – how does the chick break out of this fortress? The evolution of the tortoise shell was for a long time a mystery and this bony box offers a lot more than just protection.

More amazing animals with David Attenborough. This edition asks whether creatures can count. Was a German horse called Hans really a mathematical genius?

David Attenborough examines more fascinating creatures. Here David looks at some of nature's most extreme babies, including giant pandas and kiwis.

David Attenborough examines fascinating creatures. This episode features creatures who have an incredible ability with directions.

David Attenborough examines creatures that have fascinated us for centuries. A look at the animal kingdom's bizarre hybrids.