8/12 How the crocodile's circulatory system enables it to hold its breath underwater.
Sir David Attenborough examines the processes behind building spider's webs.
Sir David Attenborough examines why male seahorses get pregnant and give birth.
5/35 The story of Churchill's Pirates and their role in defending the Humber.
4/4 Stories include a rare baby parrot so precious it has to be hand-reared.
1/3 Following Yellowstone's wildlife in a fight to survive six freezing winter months.
The Countryfile team explore meadows, and Matt Baker discovers the art of scything.
Dr Xand van Tulleken investigates the world of performance-enhancing drugs.
The team visit Cumbria, where Matt Baker looks at the places that inspired Beatrix Potter.
1/3 A look at New Zealand's wildlife, which has been isolated since the time of the dinosaurs.