International Research Fellowship Program: Effects of Water Balance and Body Size on Thermoregulation in Australian Amphibians

Tracy Christopher R, Madison WI

Investigators

Abstract

Tracy The International Research Fellowship Program enables U.S. scientists and engineers to conduct three to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a twenty-four month research fellowship by Dr. Christopher R. Tracy to work with Dr. Keith A. Christian at Northern Territory University in Darwin, Australia. This project involves the exploration of the relationship between thermoregulation, the competing process of evaporative cooling, and body size in 10 closely related Australian frog species (in family Hylidae) that are known to have a wide range of evaporative water loss rates and body sizes. To do this, they will develop a biophysical model that uses physical and physiological properties of frogs (water loss rates, surface area, body mass, color) and climate conditions (relative humidity, solar radiation, ambient temperature) to determine what combinations of body size and evaporative water loss (EWL) rates allow frogs to thermoregulate effectively. They will then measure EWL and performance (sprint speed, hopping distance) for each species of frog across a range of environmentally relevant temperatures. Temperature selection will then be measured in the lab to determine whether each species selects a narrow range of temperatures, an indication of thermoregulation. They will also measure body temperatures and behaviors in the field using radio telemetry (larger species) and direct observations and measurements to determine whether wild frogs actually regulate temperature to a narrow range. They will then determine whether there is a relationship between EWL, body size and the precision with which a species selects temperature, with the prediction that these species with lower EWL and smaller body sizes will be better able to regulate temperatures, and therefore select a narrower range. Understanding the physical and physiological constraints on how frogs interact with their environment will lend insights into the potential impacts of human habitat modification on frog species. It will help us understand which species are more susceptible to extinction due to habitat modifications like deforestation, urbanization or even global climate change. Dr. Christian has a long history of research on temperature regulation and a great depth of expertise in the techniques and extensive knowledge of the important scientific questions involved in the study of thermoregulation.