Relationships between temperature preferences, hopping performance and water loss in northern Australian Hylid frogs

We measured preferred body temperature in a thermal gradient for twelve species of Hylid frogs (genus Litoria and Cyclorana) from the wet/dry tropics of northern Australia (near Darwin). Species in these two genera are either aquatic, terrestrial or arboreal. Resistance to evaporative water loss (EWL) ranges from nearly zero to relatively high, and appears to correlate closely with habitat type – aquatic frogs have low, arboreal frogs have high and terrestrial frogs have intermediate resistance. Temperature preferences were strongly correlated with EWL; frogs with high resistance to EWL preferred higher temperatures in the gradient and those with low resistance preferred cooler temperatures. We also measured hopping performance at temperatures from 15-37C. All species had peak performance at temperatures higher than preferred in the gradient. We suggest that higher resistance to EWL allows some species to take advantage of increased performance at higher temperatures, without desiccating and thus select higher temperatures than those with low resistance to EWL