A population of critically endangered northern corroboree frogs in Namadgi National Park, west of Canberra, is rebounding after nearly being wiped out by fire and a killer fungus, ecologists say.

During the current breeding season, for the first time in more than a decade, male frogs were heard calling in small numbers.

The fluorescent yellow and black striped frogs were once plentiful in the ACT's alpine bogs, while a southern variant of the species still lives around Kosciuszko National Park in New South Wales.

However, the deadly flesh-eating chytrid fungus, which has decimated frog populations globally, severely reduced numbers in Namadgi National Park over several decades from about the 1980s.

The frogs' habitat was then ravaged by the 2003 bushfires, which badly damaged much of the ACT's fragile sphagnum moss ecosystem.

"When the 2003 fires hit and devastated their habitat, we had serious concerns that we'd actually lost the species," ACT government ecologist Murray Evans said.

"It was very heartening to find some corroboree frogs had survived up there, and we were able to collect eggs."

The scientists took the eggs they had found to a purpose-built, climate-controlled breeding centre made from shipping containers at the Tidbinbilla Nature Reserve to Canberra's west.

In frigid conditions, mimicking the alpine climate the frogs were accustomed to, they successfully raised the eggs and now care for about 600 individuals in captivity.

In 2011, the first 200 frogs were finally released into the wild.

Those frogs should now have reached breeding age.

Frog calls lift the spirits of scientists

Scientists recently surveyed the ACT's fragile alpine bogs and found tell-tale signs of breeding - adult male frogs calling for a mate.

The northern corroboree frogs have been bred in this purpose-built, climate-controlled breeding centre made from shipping containers at the Tidbinbilla Nature Reserve. ( ABC News: Ian Cutmore )

They found two frogs calling at one site, but seven at another, which is the highest number recorded since 2003.

Although the numbers heard calling were small, it was still an exciting result for ecologists.

They believe the actual populations could be higher, as female frogs do not call and other frogs could still be immature.

"Some of the corroboree frogs we released from this institution, captive bred frogs, have survived in the wild. So they've survived four years to reach breeding age," Dr Evans said.

"It's survival of the fittest, so not all of those frogs [we released] would have survived.

"Some of them would've succumbed to natural mortality, but for corroboree frogs there's that added hurdle of chytrid fungus which is still present in the wild.

"We're hoping that this is the start of natural resistance for chytrid fungus in corroboree frogs, and hopefully one day we may actually hear the many hundreds, or even thousands that we used to hear in the 1980s."