Background and Temperature Effects on Color Change in Eastern Gray Treefrogs

Animal body coloration plays a crucial role in a wide range of ecological functions, including communication, predator avoidance, and thermoregulation. Being able to change color can further enhance these functions, as it allows organisms to fine-tune their appearance to deal with environmental heterogeneity or changes in their environment. Organisms frequently encounter conditions where requirements of camouflage and thermoregulation conflict, potentially forcing a trade-off in which function to emphasize. This may elucidate whether predator avoidance or metabolic demands represent a greater potential cost to survival and are thus under stronger selection. We examined the ecology of environment- and temperature-dependent color change in Eastern Gray Treefrogs (Dryophytes versicolor) under naturalistic conditions by allowing frogs to position themselves freely within a large outdoor enclosure filled with natural perches. We first corroborated that frogs were indeed capable of changing color and that any frog-background match was not due to environmental color preferences. We show that measures of frog coloration (luminosity, saturation, and hue) correlate strongly and consistently with the coloration of their environment, but that only frog hue significantly correlates with temperature. We also found no evidence that frogs simultaneously optimize camouflage and thermoregulation by choosing light backgrounds on warm days and dark backgrounds on cold days. Overall, our results suggest that under average temperature conditions, Eastern Gray Treefrogs predominantly adjust body coloration for camouflage.