The thermoregulatory strategy of two sympatric colubrid snakes affects their demography

Population dynamics of terrestrial vertebrates are affected by climatic fluctuations, notably in ectotherms. An understanding of the interaction between physiology and demographic processes is necessary to predict the impacts of climate change. Reptiles are particularly sensitive to temperature, but only a few studies have explored the relationship between thermoregulatory strategy and demography in these animals. Using 12 years of mark-recapture data on two sympatric colubrid snakes (Hierophis viridiflavus and Zamenis longissimus), we tested whether demographic parameters are influenced by contrasted thermoregulatory strategies. The thermophilic and conspicuous species (H. viridiflavus) grew faster than the thermoconforming and secretive species (Z. longissimus), and this difference was most pronounced in open habitats, suggesting that the metabolic benefits associated with high thermal preferences depend on environmental factors at small spatial scales. Survival varied annually in both species, but was not lower in H. viridiflavus despite a higher degree of exposure. In Z. longissimus, survival was negatively affected by low temperatures during the active season, possibly underlying an exposure trade-off.