Snakes in the North American Landscape

Loss of species is thought to result ftom reduction,. degradation, and fragmentation of habitat, But, for many species we few ideas why habitat change impact6s their populations. Reptiles are thought to be in an extinction crisis and many snake species are of conservation concern. Snakes are of conservation concern throughout North American, and important for the variety of ecosystem services they provide, including rodent population controll. Yet effective management and conservation of snakes is often hindered by a lack of basic natural history knowledge and the lack of studies to assess general population trends. Steen et al. (2012) compiled detection/nondetection data for 13 large terrestrial species from 449 traps located across the southeastern United States, and characterized the land cover surrounding each trap at multiple spatial scales. They used occupancy modeling, while accounting for heterogeneity in detection probability, to identify habitat variables that were influential in determining the presence of a particular species. Twelve competing models were used for each species, representing various hypotheses pertaining to important habitat features for terrestrial snakes.

They found considerable interspecific variation existed in important habitat variables and relevant spatial scales. For example, kingsnakes (Lampropeltis getula) were negatively associated with evergreen forests, whereas Louisiana pinesnake (Pituophis ruthveni) occupancy increased with increasing coverage of this forest type. Some species were positively associated with grassland and scrub/shrub (e.g., Slowinski’s cornsnake, Elaphe slowinskii ) whereas others, (e.g., copperhead, Agkistrodon contortrix, and eastern diamond-backed rattlesnake, Crotalus adamanteus) were positively associated with forested habitats. Although the species that studied may persist in varied landscapes other than those we identified as important, data was collected in relatively undeveloped areas. Thus, the findings may be relevant when generating conservation plans or restoration goals. Maintaining or restoring landscapes that are most consistent with the ancestral habitat preferences of terrestrial snake assemblages will require a diverse habitat matrix over large spatial scales.

Citation
Steen, D. A. et al. 2012. Landscape-level influences of terrestrial snake occupancy within the southeastern United States. Ecological Applications 22:1084-1097.