Jeanine M. Refsnider, Song S. Qian, Henry M. Streby, Sarah E. Carter, Ian T. Clifton, Adam D. Siefker, and Tyara K. Vazquez
Reptiles such as lizards maintain their body temperatures within a tolerable range by adjusting their basking behaviour. Often this means shuttling between warm and cool sites, such as a sunny rock or a shaded refuge, as their body temperature gets too low or too high. This adjustment of body temperature through basking behaviour is known as thermoregulation. The ability of reptiles to adjust their body temperature through thermoregulation could be beneficial if their habitats get hotter as a result of climate change. But what is the actual mechanism causing lizards to thermoregulate in order to match environmental temperatures – is thermoregulatory behaviour itself flexible, or are lizards genetically programmed to respond to temperature changes in a specific way? To answer this question, we attached data loggers that continuously record light level to desert short-horned lizards from warm and cool sites up a mountain in southeastern Utah. We measured lizards’ light level use continuously for a week to measure how much time they spent basking in full sun, sitting in a shrub, or buried underground. We then transplanted the lizards to the opposite site for a week so that all lizards were exposed to a new climate (that is, warm-site lizards were transplanted to the cool site, and cool-site lizards were transplanted to the warm site). We continued to record lizards’ light level use after they were transplanted to the opposite site for another week, and then we recaptured all lizards, downloaded the light level data from their loggers, and returned them to their home site. We found that transplanted lizards immediately adjusted their light level use to match the light level use of local lizards. Therefore, light-level use, one type of thermoregulatory behaviour, is a highly flexible behavior. Our results provide hope that lizards may respond to climate change by adjusting their the amount of time they spend in different light environments in order to compensate for warmer environmental temperatures.