How Canberra scientists have made silent frogs 'visible'

Researchers at the University of Canberra have developed a new way of tracking a threatened species of frog.

They've discovered that the endangered northern corroboree frog leaves traces of its DNA in ponds, sometimes for months after it's been in a particular stretch of water.

University of Canberra's Jack Rojahn performing DNA extraction during his research into the northern corroboree frog. Photo: Elesa Kurtz

University of Canberra's Jack Rojahn performing DNA extraction during his research into the northern corroboree frog. Photo: Elesa Kurtz

The animals slough off tiny traces of skin which linger in creeks where they have been. It means that scientists can analyse the water and work out which environments are good for the frogs' survival.

In the past, the best method was simply to go to likely habitats, sit on a bank and mimic the frogs to see if they responded - but the snag with that was that only older male frogs respond. For some reason, younger females are silent so this laborious process was limited in its ability to detect frogs in the area.

But now, sampling water for traces of the frog changes that. Even silent females become "visible".

A corroboree frog.  Photo: Taronga Zoo/Gary Ramage

A corroboree frog. Photo: Taronga Zoo/Gary Ramage

And that means that there's a better chance of frogs surviving when they are re-introduced to the environment - scientists have a better idea of the places where they are likely to survive.

The researchers from the university's Institute of Applied Ecology have just published the results.

“The corroboree frog is an iconic Australian species,” the lead researcher, Jack Rojahn, from the university's Institute of Applied Ecology, said.

The frogs had been decimated by disease. "Scientists have invested a great deal to conserve the corroboree frog through captive breeding programs, and we hope this study can complement the work they do,” he said.

The way the latest research was done was by putting northern corroboree eggs into to three small ponds which the researchers knew to be frog free.

Water samples were taken immediately before the introduction of eggs and then the water was tested for traces of frog one day, eight days, two weeks and more than two months later.

“This can provide information that may be critical for conservation and management decisions that aid corroboree frog survival, Mr Rojahn said.

"The next step is to continue this monitoring over the summer during breeding season, and even to other frog species."