Thermoregulation and activity patterns of three species of snakes with different lifestyles in central Mexico

Temperature is closely linked to the various lifestyles of reptiles, considerably influencing many aspects of their behaviour. Species with contrasting foraging modes or associated with different microhabitats are expected to thermoregulate in distinct ways. We sought to describe the thermal ecology of three model snake species, highlighting how their distinct lifestyles account for variation in thermoregulatory strategies. We chose the fossorial Conopsis lineata, the terrestrial Crotalus polystictus, and the semi-aquatic Thamnophis melanogaster. Following the protocol proposed by Hertz et al. (1993), we gathered data on body and operative temperatures in the field and preferred temperatures () in the laboratory. The three species exhibited a wide range of , with differences between lower and upper limits ranging from 6.4°C to 8°C. The E index of effectiveness of thermoregulation was 0.685 for C. polystictus, 0.644 for C. lineata, and 0.486 for T. melanogaster. These results indicate that C. lineata and C. polystictus are precise and active thermoregulators. C. lineata has cryptic and fossorial habits, and we propose that its efficient thermoregulation likely results from the strategic selection of thermally favourable retreat sites. Contrary to what we predicted, T. melanogaster turned out to be the least accurate thermoregulator. Its semiaquatic lifestyle can help it to maintain beneficial body temperatures with less effort since aquatic environments are more thermally homogeneous. Overall, our study shows that lifestyle affects thermoregulation to an extent in these species, but that the thermal environments they inhabit also plays a key role in delimiting their thermoregulatory strategies.