Dehydrated snakes reduce postprandial thermophily

Transient thermophily in ectothermic animals is a common response during substantive physiological events. For example, ectotherms often elevate body temperature after ingesting a meal. In particular, the increase in metabolism during the postprandial period of pythons - known as specific dynamic action – is supported by a concurrent increase in preferred temperature. The objective of this study was to determine whether hydration state influenced digestion-related behavioral thermophily. Sixteen (8 male and 8 female) Children’s pythons ( Antaresia childreni ) with surgically implanted temperature data loggers were housed individually and provided a thermal gradient of 25-45 °C. Body temperature was recorded hourly beginning 6 days prior to feeding and for 18 days post-feeding, thus covering pre-feeding, postprandial, and post-absorptive stages. Each snake underwent this 24-day trial twice, once when hydrated and once when dehydrated. Our results revealed a significant interaction between temperature preference, digestive stage, and hydration state. Under both hydrated and dehydrated conditions, snakes similarly increased their body temperature shortly after consuming a meal, but during the later period of the postprandial stage, snakes selected significantly lower (~1.5°C) body temperature when they were dehydrated compared to when they were hydrated. Our results demonstrate a significant effect of hydration state on postprandial thermophily, but the impact of this dehydration-induced temperature reduction on digestive physiology (e.g., passage time, energy assimilation) is unknown and warrants further study. Summary statement Dehydration suppresses the extent to which python increase body temperature after ingesting a meal, thus demonstrating a physiological conflict between optimizing body temperature and water balance.