The Panamanian golden frog communicates with other frogs by semaphore in the form of gentle hand waves.

It has evolved the mechanism to signal to rivals and mates above the noise of mountain streams.

Shortly after filming for the BBC One series Life In Cold Blood, the frogs had to be rescued from the wild, due to the threat of chytrid fungus.

Hilary Jeffkins, senior producer of Life In Cold Blood, said the semaphoring behaviour of the Panamanian golden frog was very unusual.

"Normally, frogs would croak to get their message across but it's too noisy," she said. "An extra mechanism they've evolved is to wave to each other."

'Final wave'

The frogs (Atelopus zeteki) were filmed at a remote location in the Panamanian rainforest. The population had all but disappeared because of a fungus that grows on the amphibians' skin and suffocates them.

The film crew was disinfected - to stop them from carrying the disease - and managed to capture unique footage of the frogs in the wild.

THE GOLDEN FROG Locals believe the frogs turn to solid gold when they die Even a sighting of one is considered lucky Golden frogs are highly toxic

Scientists were forced to remove the remaining frogs from the wild and keep them in captivity.

Hilary Jeffkins added: "The whole species is now extinct in Panama - this was one of the last remaining populations. Its final wave was in our programme."

Chytrid fungus (Batrachochytrium dendrobatidis) is a major contributor to the decline of amphibian populations around the world, threatening many species with extinction.

Sir David Attenborough brings viewers the final chapter of his epic overview of life on Earth as he transforms perceptions of cold-blooded animals in the landmark BBC One series Life In Cold Blood. It starts on Monday 4 February at 2100 GMT