Instead you will have stumbled on Taronga Zoo's reptile and amphibian unit supervisor Michael McFadden and NSW environment department's threatened species officer Rod Pietsch calling out to northern corroboree frogs as they monitor the numbers of the critically endangered amphibians in a swampy section of the mountains.

And remarkably, unique among frog species, the males are likely to answer.

Just over 200 adult frogs bred in captivity at Taronga and Tidbinbilla Nature Reserve were released at two sites in the national park on Thursday as part of a joint project to create an "insurance population" to ensure the frogs survival.

"They're a pretty cool frog… the males will yell back when you call out to them – it's about them being territorial," Mr Pietsch said.

"In February when we are back here to monitor them we'll yell out at the bog and count how many frogs respond."

Even the 49 fully-grown five-year-old frogs among the 200 released were less than three centimetres long and weighed less than two grams, making it easy to see why they are no match for heavy-hoofed feral animals like pigs, and the occasional goat or deer that wander through the Brindabellas trampling the frogs' favourite boggy habitat in search of a succulent water-loving plant.

But feral animals aren't the only threat to the endangered species, which can live until 8-years-old in the wild and up to 13-years in captivity.

Enemy number one to Australia's alpine frogs is the invasive chytrid fungus which spreads from frog to frog, including from other species that act as a host, preventing the frogs' skin from taking in water and salts.

Climate change, particularly long droughts, and weeds such as blackberries also prove a challenge to the tiny amphibians who look for boggy areas where they can hollow out their chamber-like nests in the patch of the Brindabellas managed by National Parks and Wildlife Service ranger Scott Seymour.

The frogs make up for their small stature with poisons in their skin, similar to the toxins of the poison dart frog in Central America, and anecdotally snakes looking for a froggy snack have fallen victim.

Thursday's release of the frogs gave the Brindabellas' tiny population of about 50 northern corroboree frogs a major boost.

But before the 200 black and yellow non-hopping amphibians could crawl away they were carefully photographed, weighed and measured to record each of their unique patterns to make it easier for conservationists to identify them when they return to the area in February.

Over the past four years more than 1000 northern corroboree frog tadpoles and eggs have been released in the Brindballeas.

But on Thursday, adult frogs were released for the first time to help scientists determine the best strategy to build numbers and develop disease resistance – a phenomenon that has been spotted in other species in NSW where populations have bounced back from the fungus.

"Without human intervention they'd be extinct in the next few years," Mr McFadden said.

Two months ago the group behind the program released 300 tadpoles and the effect on the population has already been noticed, with the group spotting a metamorphosed frog on Thursday.

Scientists have been unable to work out why some species are affected by the fungus and others carrying the disease are not.

"That's part of the reason we're trying to keep the population ticking over in the wild," Mr Pietsch said.

"The more in the wild, the more chance of natural selection of those without [the fungus].

"Over time it could also become less virulent."