Presence of potential predators and thermal environments of Texas horned lizards (Phrynosoma cornutum)

The Texas horned lizard (Phrynosoma cornutum) is one of thirteen species that make up the genus Phrynosoma. Their range extends from Canada to Guatemala, and they live in arid and semiarid desert regions. Due to their low motility and conspicuous foraging locations, horned lizards are often susceptible to predators. Several studies have emphasized the importance of habitat and environmental conditions to Texas horned lizards; however, less is known about their thermal biology and recent decline. My thesis aims to increase our understanding of Texas horned lizard thermal biology, predation and possible reasons of their recent decline. These aspects are essential to future conservation measures, efforts, and considerations. I conducted a predator survey using camera traps and plastic lizard models to estimate the visibly of lizards to potential hunting predators within three habitat types. Coyotes and roadrunners represent a threat to Texas horned lizards and a feasible occurrence of an overpopulation of these predators in a small and isolated habitat might have an impact on the decline besides anthropogenic factors. I also measured temperatures at ten distinct locations in which Texas horned lizards have been observed by researchers on the study site using iButtons. The purpose of this survey was to create a thermal profile of horned lizard habitat and examine the thermal constraints of their environments. Within the thermal environment of the Texas horned lizard, thermal areas (microhabitats) with diverse mean temperatures were observed and adaptations to their daily routine within their habitat were made.