Movement and Habitat Use By Reproductive Female Western Rattlesnakes (Crotalus oreganus) at the Northern Periphery of their Range

The intertwining of spatial ecology, habitat use and selection, and how these factors relate to key life history events, such as reproduction, is critical for understanding animal ecology. A broad ecological view is particularly relevant in populations that face climatic constraints and threats, such as temperate zone reptiles like Western Rattlesnakes (Crotalus oreganus). From 2017–2019, we used telemetry to study pregnant female C. oreganus in three populations spread over a 174 km stretch of the Okanagan Valley in British Columbia, Canada, with an intent to increase our understanding of female reproductive tactics, life history traits, spatial ecology, and the selection and use of parturition sites (rookeries). Females at the southern site exhibited larger home range sizes, moved farther distances (daily and postpartum), and gave birth earlier than female rattlesnakes at more northern sites. Pregnant females showed site fidelity to rookeries over consecutive reproductive years with temperature attributes, shrub, and rock cover being the variables most strongly associated with the rookery areas that they used. Rather than returning directly to hibernacula following parturition, over 55% of our telemetered females moved away from their hibernacula. Dispersing from hibernacula was presumed to be driven by need for resources. Overall, we identified habitat and temperature variables that are associated with rookeries in this northern region, as well as a high degree of variability in female C. oreganus life histories, movement, and behavior.