All six episodes from the fourth series of the documentary presented by esteemed British naturalist David Attenborough exploring some of the natural world's greatest curiosities. Among the issues examined by Attenborough are hybrid animals, the techniques creatures use to navigate and the evolution of animal shells. The episodes are: 'Animal Frankensteins', 'Finding the Way', 'Extreme Babies', 'Curious Counters', 'Incredible Shells' and 'Ferocious Fighters'.