The green and golden bell frog project was established last year by Aussie Ark, in collaboration with Macquarie University, with the aim of breeding the endangered species in large enough numbers to return to the wild.

The frogs, known for their striking bright green backs with gold patches, are being monitored in tanks at the Australian Reptile Park on the NSW Central Coast before being released into the wild.

Like many Australian frog species, they are declining rapidly.

Amphibians are among the hardest hit by the planet's extinction crisis, with at least 2000 species in danger of disappearing.

Forty per cent of amphibian species are threatened, according to a United Nations report.

Aussie Ark head of reptiles Jake Meney said frogs acted as environmental health indicators.

"So the disappearance of our amphibian species is a definite cause for concern," he said.

"In just a short time we have already had incredible success. We know that long term we can make a real difference to the species."

Professor Rick Shine from Macquarie University says green and golden bell frogs were abundant in the Sydney area just a few decades ago, but now persist only in small isolated populations.

"Bringing back these spectacular amphibians would be a major step towards restoring degraded ecosystems."

Australian Associated Press