Scientists are set to begin a hunt for the some of the world's rarest frogs in Costa Rica, including the iconic golden toad, last seen some 20 years ago.

A team from Manchester University and Chester Zoo are in Costa Rica to track down the highly endangered creatures.

BBC News will follow their trek deep into the cloud forests of Monteverde.

Amphibian numbers around the world have crashed, in part because of a deadly fungus. Costa Rica has been particularly badly hit.

Expedition leader Andrew Gray, from the University of Manchester's Manchester Museum, said: "Costa Rica's highlands used to be major biodiversity hotspots - but in many areas, amphibian populations have been completely decimated."