Habitat Use for Two Heliothermic Lizards in Longleaf Pine Savannas

Abstract

Heliothermic lizards, like Aspidoscelis sexlineata (Six-lined Racerunner) and Sceloporus undulatus (Eastern Fence Lizard), use direct solar radiation to maintain high body temperatures needed to fulfill their basic life functions. These lizards are often found in frequently burned Pinus palustris (Longleaf Pine) savannas that provide open, high-quality thermal habitat and foraging opportunities. We examined microhabitat features surrounding 42 locations where we captured lizards using drift-fences within Longleaf Pine savannas from March to May 2017 to better understand the fine-scale habitat components important for these 2 species. We used negative binomial regression, model selection (AICc), and model averaging to identify important variables associated with lizard habitat use. We found both Six-lined Racerunners (n = 52) and Eastern Fence Lizards (n = 38) used microhabitats that were characteristic of open-canopied sites (i.e., more bare ground and grass, and less litter, midstory, and canopy cover). However, their use of sites differed in the forest structure selected. The surface-dwelling Six-lined Racerunner selected sites with more stumps and the arboreal Eastern Fence Lizard selected sites with greater Quercus (oak) basal area. Management for these lizards should include activities that promote their habitat, foraging, and thermoregulatory requirements, such as frequent prescribed fire to maintain savanna-like conditions and the retention of forest structures for basking and refuge.