Frog saunas hold the key to saving species from deadly fungus
By Bianca Hall
Crouching in their “sauna”, the green tree frogs, green and golden bell frogs and corroboree frogs Anthony Waddle cares for are slimy, fat and healthy – just the way nature intended.
Some of them have come here days from death, infected with the deadly chytrid fungus that has wiped out six frog species in Australia and at least 90 amphibian species worldwide.
Anthony Waddle with a green and gold bell frog.Credit: Steven Siewert
The parasitic fungus chytrid invades the skin cells of amphibians, hampering their ability to absorb moisture and electrolytes through their skin. Without the ability to absorb water and nutrients, infected amphibians die.
But chytrid can’t survive in temperatures above 28 degrees. Enter: the frog sauna.
Waddle and his colleagues started their chytrid-killing experiment by making stacks of Besser blocks for frogs to hide in.
When the blocks alone let too much cold wind in, the team picked up some cheap greenhouses from Aldi, creating a simple – but very effective – environment to protect frogs, and kill the fungus making them sick.
Frog saunas not only keep frogs warm, but could also help these vulnerable species beat the deadly chytrid fungus.Credit: Anthony Waddle
During winter, when the chytrid fungus flourishes, researchers have scoured known frog hotspots in Sydney to bring frogs to Macquarie University for treatment.
“We brought them in the middle of winter, and of course, they’re all coming in sick and some of them very sick,” Waddle said.
Happy frogs inside their sauna at Macquarie University.Credit: Anthony Waddle
“In the winter, their physiology is really depressed, and the chytrid is thriving because it’s cold. This is when you see mass die-offs of populations, and this is the critical time for us to do conservation.”
The genius of the frog saunas is their simplicity. By creating “Jenga towers” of bricks, researchers created habitats with different humidity and heat levels, allowing frogs to move between holes in the bricks and adjust to different temperatures as they go.
Inside, the humidity is as high as 100 per cent, perfect for frogs that secrete mucus from their skin (frogs don’t sweat, as such). The team leaves the greenhouse flaps open, so the frogs can leave if they choose, but they are showing no signs of wanting to leave their greenhouse saunas.
“They’re all free from chytrid, and they’re all super-fat and healthy,” Waddle said.
In May, Waddle won a prestigious Future for Nature award for his work saving amphibians from the deadly fungus.
The next step, he said, would be to get the rescued frogs breeding and then release them back into the wild in summer – complete with antibodies that would protect them against future chytrid infections.
“It’s actually the first time, to my knowledge, that someone’s done a release where we’ve attempted to mitigate chytrid in Australia,” he said.
“They’re declining in the wild because of chytrid … once it’s in the environment, it’s there forever. It’s part of the ecosystem, so you have to manage it.”
Chytrid is an invasive species and amphibian pathogen thought to originate from the Korean peninsula.
“It’s actually the worse invasive species ever … nothing else has caused as many extinctions,” Waddle said.
“You think about things like cane toads and cats and rats … it’s worse than all of those. Just in Australia, we’ve lost six species [to chytrid], and it happened very quickly.”
Researchers have created about 70 frog saunas in Greater Sydney, and have compiled social media clips demonstrating how anyone can build a frog sauna in their backyard.
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