Snakes and other ectotherms must select microhabitats that enable them to obtain adequate food resources, confer protection from predators, and enable them to thermoregulate effectively. Therefore, microhabitat characteristics such as vegetation structure and availability of below-ground refuges can play an important role in resource selection and habitat quality for reptiles. We assessed the thermal ecology and microhabitat selection patterns of the Great Basin rattlesnake (Crotalus lutosus) within a semi-arid montane region of eastern Nevada (Great Basin National Park). We surgically implanted rattlesnakes with radio transmitters and temperature dataloggers (n = 29), and we obtained locations for each snake 1-2x per week during the activity season. In addition, we deployed operative temperature models (n = 63) at a wide range of available above and below-ground microhabitats within our study area. We are using this information to assess how snakes select habitats throughout the activity season. Moreover, by comparing available operative temperatures with field-active body temperatures we will be able to study how snakes use microhabitats for thermoregulation and assess seasonal and diurnal changes in thermal preferences. We hope to learn how a changing climate affects body temperatures of rattlesnakes and how their movement behavior influences resource selection.