Fungal infections reduce frogs’ tolerance of heat

A new study published in the international journal Scientific Reports shows that fungal infections reduced the heat tolerance of frogs by up to 4 degrees Celsius.

"We have seen an increase in animal and plant diseases, and we have a lot to learn about how this will impact wildlife as the climate continues to change," said Brett Scheffers, an author on the study and assistant professor of wildlife ecology and conservation at the UF Institute of Food and Agricultural Sciences.

Scheffers and a group of international colleagues investigated interactions between fungal disease and a host's tolerance of hot temperatures. In this case, they examined frogs infected with a microscopic skin fungus called Batrachochytrium dendrobatidis.

They first infected frogs with the fungus in a laboratory and then measured how well the infected frogs as well as healthy control frogs could tolerate heat.

"Infections dramatically reduced the heat tolerance of the frogs. We also reviewed the literature and found that numerous other animal groups become more sensitive to heat when infected with parasites and pathogens. This suggests that this phenomenon might be widespread," said Sasha Greenspan, the lead author of the study and a researcher at James Cook University in Australia.

In frogs and other animals that depend on external sources for body heat, behaviors that raise body temperature, such as basking in the sun, may directly kill parasites or strengthen the host's immune system, helping the animals to cope with infections, researchers said. This action is similar in effect to when humans get a fever to beat the flu, Scheffers said.

"However, increased sensitivity to heat from infections may discourage these protective behaviors, tipping the balance in favor of the parasite," said Greenspan.

"Considering that the climate is becoming warmer and more extreme, climate change and new diseases might work together to drive species to extinction, but in a way that isn't always obvious -- changing of the animal's tolerance of heat," Scheffers said. "This is just one of the many hidden consequences of climate change."