The mystery of the disappearing frogs

This week we're looking at extinction. The deadly fungus that's killing amphibians, the story of the Dodo, plus why discovering that whales 'sing' helped to save them. Also, the book that changed attitudes to the environment and the 'Frozen Zoo' that aims to preserve endangered DNA for future generations. (Photo: dead frog infected with Chytrid Fungus. Credit: Forrest Brem)