A new species of frog that has green blood and turquoise bones has been discovered living in a former stronghold of Pol Pot’s Khmer Rouge forces.

The Samkos bush frog is one of four previously unknown species discovered as part of a project to rebuild the country’s science base from the devastation left by the dictator’s regime.

The unusual colour of the blood and bones is caused by biliverdin, a pigment that would usually be processed in the liver as a waste product but which in the frog is passed back into the bloodstream.

Conservationists believe that the pigment helps to camouflage the amphibian because it shows green through the translucent skin. It is suspected that it also serves to make the frog, Chiromantis samkosensis, taste nasty to predators. Jeremy Holden, a naturalist for the conservation group Fauna & Flora International (FFI), who discovered the bush frog, said: “When I found the frog, I had a thrilling suspicion that we were looking at an entirely new species of amphibian.”

The species is so small and well camouflaged in the jungle habitat that researchers are able to track it down only by listening for its distinctive “rising trill” call. It is thought to breed in temporary pools created by heavy rain.

Smith’s frog, Rana faber, the Aural horned frog, Megophrys auralensis, and the Cardamom bush frog, Philautus cardamonus, are the other three species discovered by researchers from FFI during their surveys of Cambodia in the Cardamom mountains.

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