Spatial Ecology of North American Pitvipers (Viperidae: Crotalinae): A Review and Meta-Analysis

We review literature on telemetry and movement of North American pitvipers (Viperidae: Crotalinae) to identify geographic and taxonomic biases in research; conduct meta-analyses using commonly reported spatial metrics; characterize best practices in methodology, reporting, and analysis; compare general patterns of movement and behavior across species; and suggest directions for future research in this field. We found large disparities across species and locations, with four rattlesnake species (Crotalus horridus, Sistrurus catenatus, C. oreganus, and C. viridis) accounting for more than half the total studies and very limited spatial ecology research outside of the United States and Canada. Several different metrics for movement distance and space use are reported in this literature, but perhaps the most useful for general comparisons are average distance moved per day for movement and both minimum convex polygons and a kernel density estimator for space use. Our meta-analysis revealed a modest relationship between body size and both movement distance and space use, with larger bodied species moving further and occupying larger home ranges. Nonetheless, a substantial amount of variation in these parameters is not explained by body size. Among the most reported spatial patterns across species were increased movement of adult males compared with females (particularly during the breeding season) and decreased movement of pregnant females compared with nonpregnant females; however, we discuss some apparent exceptions to these near-ubiquitous patterns. Spatial ecology studies also frequently reported aggregation behaviors for overwintering and gestation and commented on high degrees of site fidelity, underscoring the overarching impact of seasonal environmental conditions on pitvipers in temperate climates. Future research might focus on neglected Mexican species, social behavior, and use of new technology (global positioning system trackers, accelerometers, tracking drones, and videography) to continuously monitor individuals.