“Mini med spa” for frogs helps cure deadly chytrid infections

Newly designed heated shelters will help endangered frogs fight against the fungal disease chytridiomycosis, which has driven at least 90 amphibian species to extinction worldwide.

The fungus that causes chytrid – Batrachochytrium dendrobatidis or Bd – thrives at low temperatures. Seasonal outbreaks of chytrid usually occur during winter and early spring in temperate regions, leading to high mortality which can limit population recovery and reintroduction efforts.

The artificial froggy hotels are built from readily available materials, such as black bricks and PVC greenhouses, and are passively heated by the sun. The resulting temperature is nice and toasty for the frogs, but inhospitable to the fungus.

“The whole thing is like a mini med spa for frogs,” says Dr Anthony Waddle, a researcher at Macquarie University and lead author on a paper describing the research, published in Nature.

“In these simple little hotspots, frogs can go and heat up their bodies to a temperature that destroys the infections.

“In the 25 years since chytrid was identified as a major cause of the global collapse of amphibian populations, our results are the first to provide a simple, inexpensive and widely applicable strategy to buffer frogs against this disease.”

The study was carried out on the endangered green and golden bell frog (Litoria aurea), an Australian species that has disappeared from 90% of its former range since the arrival of Bd. During colder months, these frogs shelter on land and raise their body temperatures by basking.

A green and golden bell frog
A green and golden bell frog (Litoria aurea). Credit: Ken Griffiths/Getty Images

The researchers studied the frogs in outdoor mesocosms – experimental systems that mimic natural ecosystems. They found that frogs with the ability to thermoregulate using the artificial hot-spot shelters were able to more rapidly recover from chytridiomycosis.

They also show that frogs cured of Bd through heat can develop a form of acquired immunity, making them 23 times more likely to survive second exposure compared to frogs with no prior infection.

“Lowering mortality rates and boosting their immunity to chytrid is the key to protecting amphibians from this disease, which is now endemic around the world,” says Waddle.

Once chytrid spreads to a new environment it will likely become a permanent part of that ecosystem. For endangered species affected by chytrid, manipulating the conditions of their microhabitats could mean the difference between their persistence or extinction.

Senior author Rick Shine, from Macquarie University’s School of Natural Sciences, says this study has demonstrated a simple intervention which can easily be scaled up.

“Chytrid isn’t going away, but our behavioural ecology intervention can help endangered amphibians co-exist with chytridiomycosis in their ecosystems.”

The refuges could be rapidly adopted by wildlife managers and the public for the green and golden bell frog, as well as other species in cool climates that prefer temperatures which exceed the thermal limits for Bd.

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