The "sauna" is built of hollow bricks and heated by the sun. But when the green tree frogs, of the species Litoria aurea, crawl in, they are unaware that the "spa treatment" is not only pleasant - it can also protect against a fungal disease that is ravaging amphibian life globally.
Chytridiomycosis, often called chytrid, is a waterborne disease that burrows into the frogs' skin and attacks their bodies. It has led to global mass death, sometimes called an "amphibian apocalypse", among frogs, toads, and salamanders.
500 species of amphibians have declined in number and 90 have been wiped out by the fungus's advance, according to Anthony Waddle, biologist at Macquarie University in Australia.
Chytrid is the worst pathogen ever, he says to news agency AFP.
Living in boxes
Previously, the solution to protect endangered frogs was to catch them to treat them, according to Waddle.
Nothing has ever caused so much destruction. In Australia, we have frogs that only live in glass boxes now. This is a big, ongoing problem.
Waddle has led a research group that experimented with the sauna solution, where it turned out that the frogs chose to crawl into the heat if they got the chance. But it also helped against chytrid, according to the study published in Nature. In the heat, the fungus could not grow on the frogs, which allowed the animals to fight off the infection.
Over 40 percent of the world's amphibian species are threatened with extinction, making them one of the most vulnerable groups among vertebrate animals. Major concerns are loss of habitats, climate change, and chytrid.
Other attempts
Heat treatments have been tested on other species, but without any evidence that it worked, according to Andrew Cunningham, professor at the Institute of Zoology in London, who first identified the fungal disease. They have tested increased sun exposure in the frogs' natural habitat as well as artificial warming of ponds.
We have continued to have deadly outbreaks of chytridiomycosis, and the only way to stop these has been to treat the frogs with antifungal medication, he has said to The Guardian.
Maybe the technique is species-specific, but unfortunately, I doubt that it is a universal solution to the global threat from chytridiomycosis among amphibians.
Waddle believes that his sauna is a creative solution to a serious problem - but emphasizes that more measures are needed if frog populations are to survive.
No solution will work for all. Frogs are so different.
Chytridiomycosis is caused by the fungal organism Batrachochytrium, also called chytrid fungus. It causes widespread disease and death among amphibians worldwide. In Sweden, the disease has been detected since 2010 in wild amphibians, and the spread of the infection is occurring across the country.
Chytrid is considered a crucial, sometimes decisive, factor in the decline and even extinction of many amphibians, especially in more tropical regions.
The fungus attaches itself to the amphibians' outer skin layer and causes a thickening of the outer skin, or skin ulcers. Disruptions in salt balance and oxygen uptake through the skin can then lead to death.
The fungus does not thrive in water temperatures higher than around 25 degrees.
Source: The National Veterinary Institute
