Microhabitat Selection by Prairie Rattlesnakes (Crotalus viridis) at the Northern Extreme of their Geographic Range

Prairie Rattlesnakes (Crotalus viridis) are a species of conservation concern in Canada because of suspected population declines. Data on the habitat selection of Prairie Rattlesnakes at northern range limits are essential to inform management strategies and implement recovery plans in Canada and other northern regions. We used radio-telemetry and generalized linear mixed models to create resource selection functions for Prairie Rattlesnakes (N = 23) in and around Grasslands National Park, Saskatchewan, Canada. Eight habitat variables were compared between used and available sites to quantify microhabitat selection. We found that Prairie Rattlesnakes select for specific sites (i.e., within 1 m) with shrub cover and burrows and avoid bare ground. Shrub cover was two-times higher at used sites compared to available ones, while bare ground showed the opposite trend. In addition, two-thirds of all snake location points were within 1 m of a burrow, which suggests that retreat sites are important. None of the habitat variables measured at 10 m from used points were significant predictors of rattlesnake habitat selection, indicating that rattlesnakes select habitat at a very fine level. Northern range limits present a thermally challenging environment in which burrows and shrubs are likely crucial for thermoregulation. In addition, these retreat sites likely provide a prey source, protection from predators, and suitable areas for reproduction. Retreat sites such as burrows and shrubs are therefore critical components of habitat for Prairie Rattlesnakes and should be included in management strategies for the species.