Hot frog bodies fight deadly infection
FROGS THAT MAINTAIN high body temperatures are better protected against a deadly fungus, according to research sponsored by the Australian Geographic Society.
The chytrid skin fungus which targets amphibians, has decimated frog populations worldwide. However, scientists have now discovered that when wild frogs spend more time in warm conditions, they are less likely to be infected by the disease.
“This study is the first to show that the temperatures a frog spends its time at, affects its probability of infection,” says Dr Jodi Rowley one of the researchers behind the study at the Australian Museum.
How frogs control their body temperature
The findings, published in the journal Scientific Reports, reveal that if frogs maintain body temperatures of 25°C or higher more than three-quarters of the time, they are unlikely to be infected.
Frogs rely on the external environment for heating and cooling. “Their body temperatures tend to resemble environmental temperatures, but they can control them to some extent by basking in the sun to warm up, or avoiding sunlight to cool down,” says Professor Ross Alford, study co-author at James Cook University.
Over the course of three years, the AGS-sponsored researchers tracked the body temperatures of 128 frogs from three different species, in the rainforests of north-eastern Australia.
“Each frog was fitted with a tiny radio-transmitter, attached via a tailor-made waist-belt, that allowed us to find it every day and night for up to 16 days at a time,” Jodi says.
“We then took the frogs’ temperatures using infrared thermometers,” Ross adds. Infected frogs were more often detected in cooler months and at higher (and therefore cooler) altitudes.
“Prior to this study, nobody knew what body temperatures frogs reached in the field, and nobody knew how field body temperatures might affect chytrid infections,” he says.
Cooler frogs suffer more infections
Their research builds on previous experiments that were conducted in laboratories in the early 2000s. These studies showed that the fungus grows fastest at 17–25°C. “Infected captive frogs were cured simply by raising the temperature,” says Jodi.
Chytrid fungus has been associated with declines and extinctions in hundreds of species of amphibians worldwide. Researchers hope this study will aid the captive management of endangered frogs, and affect the way threatened species are managed in natural environments.
Professor Dale Roberts, a biologist at the University of Western Australia, Perth, agrees. “This study is an outstanding demonstration of how much and how little we know about the amphibian chytrid fungus in the real world,” he says. “Knowing in detail how frogs use their environment might be a powerful tool for predicting species-specific chytrid impact.”
Dale adds that the knowledge could also affect the way captive breeding and release programs are run for specific species.