Habitat specificity and home-range size as attributes of species vulnerability to extinction: a case study using sympatric rattlesnakes

Large home-range size and habitat specificity are two commonly cited ecological attributes that are believed to contribute to species vulnerability. The eastern diamondback rattlesnake Crotalus adamanteus is a declining species that occurs sympatrically with the more abundant canebrake rattlesnake Crotalus horridus in a portion of the south-eastern Coastal Plain, USA. In this study, we use the ecological similarities of the two species as experimental controls to test the role of home-range size and habitat specificity in the imperilment of the eastern diamondback rattlesnake. We used analysis of variance to investigate differences in home-range size between the two species, and home-range selection was modeled as habitat use versus availability with a case control sampling design using logistic regression. We failed to detect differences in home-range size between the two species; therefore, we could not identify home-range size as an attribute contributing to the imperilment of eastern diamondback rattlesnakes. Eastern diamondback rattlesnakes selected pine savannas to a degree that suggests that the species is a habitat specialist. Of the two factors examined, habitat specificity to the imperiled longleaf pine ecosystem may be a significant contributor to the decline of the eastern diamondback rattlesnake.