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Abstract Hybridization between species provides unique opportunities to understand evolutionary processes that are linked to reproductive isolation and, ultimately, speciation. However, the extrinsic factors that limit hybridization are poorly understood for most animal systems. Although the spatial ecology of individuals in natural habitats is fundamental to shaping reproductive success and survival, analyses of the spatial ecology of hybrids and their parental groups are rarely reported. Here, we used radiotelemetry to monitor wild rattlesnakes across an interspecific hybrid zone (Crotalus scutulatus and Crotalus viridis) and measured movement parameters and space use (utilization distributions) of individuals to evaluate the hypothesis that hybridization resulted in transgressive or atypical movement patterns. Unexpectedly, of the spatial metrics we investigated, we found that hybrids were very similar to parental individuals. Nonetheless, hybrids did show increased patchiness of core utilization distributions, but this result is likely to be driven by increased habitat patchiness in the hybrid zone. Overall, we did not find evidence for overt extrinsic barriers to hybridization associated with spatial ecology; thus, we suggest that the close evolutionary history between the two parental species and their ecological and behavioural similarities are likely to increase the probability of hybridization events in this unique region of New Mexico. 

Abstract Rattlesnakes are widespread mesopredators that are themselves killed and eaten by a host of other predators, including birds of prey and carnivorous mammals. Although anecdotal accounts of rattlesnake depredation are common, there are few quantitative data on encounter rates between rattlesnakes and their predators. Here we review a large database of encounters between rattlesnakes and their predators recorded from field videography of snakes in the sit-and-wait phase of their ambush hunting strategy. We found that, across 8300 hours of observation, adult rattlesnakes of six species and multiple populations exhibit low encounter rates with predators; furthermore, when predators were encountered, we never observed them to attack or kill coiled snakes. Thus, we propose that rattlesnakes are preyed upon while performing other, riskier behaviors associated with moving through the landscape. We also discuss why rattlesnakes are at low risk of predation while hunting on the surface.