Effects of incubation temperature on behavior of hatchling pine snakes: implications for reptilian distribution

Incubation temperatures in vertebrates affect incubation periods, and in some reptiles incubation temperature determines sex ratios and some limited behavior. Here I present evidence that incubation temperature in pine snakes (Pituophis melanoleucus) affects not only incubation periods and posthatching behavior in the laboratory, but also the behavior of hatchlings required for successful emergence and survival. These behavioral differences have evolutionary implications for selection of hatchlings from particular temperature nests. With increasing temperature, incubation periods decreased in the laboratory. In addition, incubation temperature affected hatching and emergence times as well as movement speed and foraging ability. Hatchlings from medium temperature conditions emerged from nests in the field in less time than hatchlings incubated at high or low temperatures, and hatchlings from low temperatures moved slower and were less able to capture and eat mice in the laboratory than hatchlings incubated at medium or high temperatures. Taken together, these laboratory and field experiments suggest that hatchlings from low temperature nests, compared to those from higher temperature nests, would be less able to emerge, find food, and locate hibernation sites prior to the onset of cold temperatures in the New Jersey Pine Barrens. These results suggest that incubation temperature affects a whole range of behavior and that distributional ranges of reptiles and other poikilotherms could be affected by summer temperatures (via incubation period and subsequent behavior) as well as ambient winter temperatures.