The Pretoria zoo is going to start a breeding programme with 10 critically endangered Pickersgill's Reed Frogs to help save them from extinction.

A special "frog room" had been equipped for the six-month project, the zoo's reptile expert Mike Adams told the newspaper

According to Beeld, the small, yellow-green frogs, are smaller than a man's thumb and are endemic to South Africa, but are found in only 18 small habitats.

"Because they are so small, conservation has been difficult," the newspaper quoted Adams as saying.

The Johannesburg Zoo had caught 40 of the frogs, of which 10 had been moved to Pretoria.

"No one knows at this point how to breed the frogs, so with these 10 we hope to write a breeding manual so that the programme can be replicated elsewhere," Adams said.

Pretoria zoo spokeswoman Angeline Schwan told Beeld amphibians were among the most endangered species on earth.

"There are about 7000 species, of which 3900 are threatened and 170 are apparently already extinct," she said.