Habitat management alters thermal opportunity

1. Ectotherms engage in behavioral thermoregulation to optimize body temperatures, however, thermoregulatory effort varies across species, over time, and among habitats. Classic cost-benefit models of ectothermic thermoregulation postulate that ectotherms should increase thermoregulatory effort when the benefits of thermoregulatory behavior outweigh the costs (Huey and Slatkin, 1976). However, alteration of habitat via land management may lead to unforeseen shifts in microclimate that change associated costs and benefits. In light of anthropogenic impacts on natural habitats, thermoregulatory effort should be examined in cases where land management results in environmental temperatures that deviate from the preferred temperature range of a given species. 2. We examined how habitat management alters microclimates and influences activity time, thermoregulatory behavior, and thermal physiology in a lizard (Sceloporus woodi) whose range has been significantly reduced due to habitat loss. We compared populations from two ecologically distinct habitats: longleaf pine and sand pine scrub, which have very different management histories. Daily surveys were conducted in each habitat type while environmental temperatures were recorded simultaneously with biophysical models. 3. Thermal performance curves differed between populations such that physiological performance was optimized in each environment. Longleaf pine habitat had greater thermal opportunity because cooler microclimates were available on arboreal perches. In longleaf pine habitat, lizards were able to stay active longer and thermoregulate more effectively. Regardless of habitat, thermoregulatory effort of S. woodi increased when thermal quality of habitat was low. However, when unfavorably high temperatures were experienced, the thermoregulatory effort increased significantly. 4. Our results demonstrate that ectotherms can afford to imprecisely thermoregulate when habitat thermal quality is poor due to cooler environmental temperatures. However under unfavorably hot environmental temperatures, lizards must precisely regulate body temperature in spite of any costs. These results further demonstrate that habitat management has major implications on species-specific thermal opportunity, thermoregulatory behavior, and thermal physiology, such that shifts in thermoregulatory behavior may lead to higher energetic costs, enhanced predation risk, and constrained activity times.