Living in the city has its advantages: thermoregulation behavior and activity time in the Torquate lizard

Abstract

Urban development transforms natural ecosystems, imposing novel challenges on the organisms that persist within them. One such change is the "heat island" effect, which involves higher temperatures in urban areas compared to non-urban areas. Therefore, identifying the traits related to persisting in or colonizing urban environments is crucial for developing conservation plans for urban vertebrates, especially reptiles, which are highly dependent on ambient temperature. This study examines thermal traits and potential activity time in Sceloporus torquatus lizards inhabiting an urban and a non-urban site in central Mexico. We assessed body temperatures in the field, thermal preferences in a laboratory gradient, and critical thermal limits. We used biophysical modeling to simulate annual activity time under two vegetation cover scenarios corresponding to these urban and non-urban environments. Despite finding similar body and preferred temperatures in the two populations, lizards from the urban site were larger, showed lower critical thermal values, and were more effective in thermoregulation, as measured by their lower deviation from preferred temperature. Lizards from the urban site also likely had more hours of activity across the year, likely due to warmer conditions associated with the urban heat island effect. While these traits may offer short-term advantages, continued increases in temperature could reduce daily activity windows and challenge persistence in this urban site. Our findings underscore the importance of considering both physiological thresholds and habitat features, such as vegetation cover and microhabitat structure, when assessing how ectothermic species respond to urban pressures.