Abstract

Many snake species make lengthy linear migrations between overwintering sites and summer foraging or mating habitats. Although mountainous topography may restrict migratory movements, most previous studies on migratory snake populations have occurred in areas with low to moderate topographic relief. The objectives of this study were to describe the movement patterns of Prairie Rattlesnakes (Crotalus v. viridis) in a mountainous landscape, compare those patterns to those of migratory snake populations from areas with lower topographic relief, and test for variation in movement patterns between sexes and among years. We used radiotelemetry to monitor the movements of 21 male and 6 nonpregnant female Prairie Rattlesnakes in the Frank Church Wilderness in central Idaho during the summers of 2006–2008. Mean total distance moved during the entire activity season in 2008 was 4.46 km (range 1.38–7.67); mean maximum distance moved from the hibernaculum was 1.46 km (range 0.69–2.71). Although the movement distances reported here are intermediate to those reported for other migratory snake populations, they are similar to some distances reported from areas with low to moderate topographic relief. This suggests that rattlesnakes are capable of making considerable movements in a mountainous landscape, although factors such as prey availability could also contribute to differences in reported movement distances. Rattlesnakes displayed moderate fidelity to summer activity areas but had similar mean bearings during outbound migration across multiple years. We hypothesize that linear migrations reported from rattlesnakes in many populations actually represent the most-direct movement to annual foraging areas rather than true searching movements.