23 November 2004

Charles Darwin University researchers in the School of Science and Primary Industries are hoping to unlock the biological secrets of Northern Territory frogs through a three-year $220,000 Australian Research Council Discovery Grant.

Project team member Dr Chris Tracy with the Northern Burrowing Frog

“For more than 30 years there has been scientific contention about whether or not amphibians can regulate their body temperature by exposure to heat,” Associate Professor Keith Christian said.

“This is a basic aspect of amphibian biology, and in order to understand the consequences of habitat or climate change on frog populations, we need to understand exactly how frogs interact with their environment.

“While many reptiles actively control their body temperatures by using behaviours such as basking in the sun, the situation for amphibians is more complicated because they have wet skin.

“A frog sitting in the sun will increase its rate of evaporation, so, depending on the other conditions at the time, its body temperature may either go up or go down. On the other hand, many people have observed behaviour in frogs that appears to be related to thermoregulation.”

Dr Christian and Associate Professor of Engineering, Friso DeBoer, will lead the research team. They will be joined by Dr. Chris Tracy, who is currently a National Science Foundation (USA) International Research Fellow at Charles Darwin University and Professor Richard Tracy of the University of Nevada in Reno who was a Visiting Scholar sponsored by the Tropical Environmental Area of Strength at Charles Darwin earlier this year. The project will begin in 2005.

“The only way to determine whether or not amphibians thermoregulate is to combine observations of what the animals are doing with computational models of the energy balance of the animals.“

“Therefore, in addition to field research, the project will include the design and construction of a wind tunnel in which the heat transfer of frogs will be studied under a range of conditions,” Dr Christian said.

“Results of these experiments can then be used to solve the energy balance of an animal by simultaneously taking into account factors such as the heat gained by radiation and the heat lost by evaporation.”

In a previous ARC funded project, Dr Christian and Charles Darwin University’s Associate Professor David Parry studied the mechanisms that some tree frogs have to reduce their water loss.

“Frogs that have some resistance to water loss have greater potential for controlling their body temperatures. That is why the Northern Territory’s Top End is the perfect place to do this project: we have about 15 species of frogs that have some resistance to water loss, and they vary from only a small amount of resistance to a very substantial resistance. It is a perfect model system with which to work,” Dr Christian said.