Yellow-spotted bell frogs, previously thought extinct, released at Mulloon Natural Creek Farms

Twenty frogs have been set free at Mulloon Creek Natural Farms as part of a trial program to see how they fare in the wild. Radio transmitters have been attached to the frogs to track progress.

For 30 years the yellow-spotted bell frog was presumed extinct, but in 2009 a small colony of the frogs was found on a small stretch of creek line north of Yass.

Researchers recovered tadpoles and developed an in-situ colony at Taronga Zoo. The zoo's fauna supervisor Michael McFadden said the species had been "secured" at the colony.

"Over the last couple of years now we've had a bit of success breeding them and we have been trialing reintroduction at a couple of sites," he said.

Since 2017, six clutches of eggs have been released by frogs at the zoo and Mr McFadden said close to 2000 frogs had been reintroduced back into the wild.

Mulloon is the third site where the frog has been reintroduced with releases at two other sites in the Southern Tablelands.

"The folks at Mulloon have got some beautiful rehabilitated creek line which looks like absolutely excellent bell frog habitat," said Mr McFadden.

Mulloon Creek Natural Farms is well known for its work in regenerating river landscapes by employing natural interventions to get the water running again and Mr McFadden said this was ideal habitat for the frogs.

While the drought posed a risk to the frogs it does lessen the chance of the frogs developing the chytrid fungus - an infectious virus that affects amphibians worldwide as the virus thrives in cold and wet conditions.

"I was concerned... why would they be releasing the frogs in the middle of the worst drought we've ever had, even though there is water in the creek," said Mulloon Institute project coordinator Peter Hazell.

"But they suggested that it's quite possibly the best time to release them because the chytrid fungus would be the least active during the drier times."

Unfortunately for this batch of 20 frogs, the survivability does not look great. A few have already been taken by snakes and another by a kookaburra. Two more have kicked off their radio transmitters, Mr Hazell said.

"This is just a pilot program to figure out where they go and effectively what eats them... and whether they get the chytrid virus," he said.

"I don't think they are expecting any survivability for this lot but as they continue to breed their frogs in captivity they will probably start to undertake more mass translocations back into these particular sites.

"That's the thing about frogs, everything wants to eat them."

Despite the losses so far, if the program is deemed a success they have planned to do a "rolling release" of the frogs at Mulloon. The plan is to reintroduce thousands of frogs back into natural habitats across the Southern Tablelands and surrounds.

"The species have been secured in the in-situ colony at Taronga Zoo and now we are taking the first steps at reintroduction and over the next couple of years we will be furthering it," said Mr McFadden.

"Potentially at Mulloon and at other sites as well to see where we can hopefully establish some self-sustaining species of the population again.