Journal of the Australian Native Plants Society Canberra region (Inc)
World-leading experiment reintroduces Green & Golden Bell Frogs to Canberra
By Jarrod Sopniewski
Jarrod is a conservation biologist and Postdoctoral Research Fellow at University of Canberra. He was the June 2026 speaker for ANPSC Monthly Members Meeting.
Chytrid fungus has devastated frog species across the world
Around 50 years ago, herpetologists around the world noticed frogs were disappearing rapidly, even in pristine environments.
Various environmental causes were investigated, such as pollution and increased UV radiation. Only in the 1990s did Australian PhD student Lee Berger observe that declines seemed to follow a disease-like trajectory. In 1996 she discovered the culprit, the fungal pathogen chytrid fungus (Batrachochytrium dendrobatidis).
We now understand that chytrid, likely evolving in Korea but spread globally by humans, causes the disease chytridiomycosis in many frog species. It feeds on keratin in frog skin — a vital organ — often resulting in severely impaired skin function or death.
At least 500 amphibian species have suffered declines due to chytridiomycosis, nearly 100 going extinct. After this worldwide devastation, amphibians are the most threatened taxonomic group, 41% of known species being threatened with extinction.
Australian and Canberra frog species have been badly affected
Chytrid has taken a heavy toll on Australia’s frogs. For example, Queensland’s gastric brooding frogs were quite distinctive from any other frog genus in Australia or the world. The two species were first formally described as recently as the 1970s, but haven’t been seen since the 1980s, and have been declared extinct.
However, in the years since the discovery of the fungus, important conservation patterns have been observed.
Firstly, not all frogs are negatively affected. Many, such as the common froglets (Crinia signifera) of Canberra, can carry high disease loads but seemingly be unaffected. This renders the eradication of chytrid in the wild near impossible.
Second, there are strong environmental patterns, linked to both where frogs decline and where they persist. The most obvious factor is temperature. Frogs have declined from cooler places, but often have hung on in warmer parts of their distribution. Other environmental drivers also appear to support frog survival.
Consider the Green & Golden Bell Frog (Ranoidea aurea), once among the most common frog species in southeastern Australia including Canberra. It rapidly disappeared from over 90% of its distribution once chytrid arrived. It now exists in only a few locations in generally warmer and more saline regions of its former range.
These refuges — where chytrid-declined frogs seem to be able to survive — give us insights into ways we might be able to return them to their former distribution.
Specifically, we know heat and salt can thwart chytrid and therefore support frog populations that might not otherwise survive. Could we simply provide frogs with ‘heat’ and ‘salt’ in environments that otherwise lack these features, to help them survive alongside chytrid?
Canberra’s experiment to reintroduce the Bell Frogs
Aided by volunteer groups, researchers at the University of Canberra are currently trialling this approach to reintroduce Green and Golden Bell Frogs to the ACT.
Although they used to be one of the most common frogs in the region, without any support, they wouldn’t survive chytrid. Researchers have manipulated the environment in two ways. ‘Frog saunas’ (non-powered greenhouse-like structures that exploit sunlight, achieving temperatures harmful to chytrid but not frogs) and ‘salty plunge pools’ (small ponds built around the perimeter of wetlands, with salt added to them) have been installed at 15 different locations across urban Canberra.
In February 2026, nearly 500 Green & Golden Bell Frogs were released at these locations, the first time in nearly half a century the species has been wild in the ACT. Researchers ‘immunised’ the frogs in the lab before releasing them. Frogs were infected with a mild strain of chytrid and assisted to ‘clear’ the disease, in the hope that prior exposure will help them survive chytrid in the wild.
The project is still in its infancy, but initial signs have been encouraging. Over the first few months, frogs appeared to survive their initial release strongly and quickly acclimated to their new wild homes. Importantly, they appeared to make use of their saunas and plunge pools, which will be critical for their long-term survival.
Excitingly, at least one pair of frogs is known to have reproduced in a plunge pool, with many tadpoles and tiny bell frogs seen in Gungahlin in April.
During the cooler months the frogs will face their biggest challenge, this being the period when chytridiomycosis will be at its most threatening. Researchers are hopeful, though, that come spring 2026, healthy frogs will emerge from their winter-hideaways, take saunas and salty plunges, then produce another generation of frogs to make use of these interventions. If this approach works, perhaps saunas and plunge pools could be used to save chytrid-affected frogs across the globe.
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