Sonoran desert snake communities at two sites: Concordance and effects of increased road traffic

We surveyed the snake communities at two locations in the Sonoran Desert of southcentral Arizona. From 1982-2009, we used roadways as sampling transects and recorded all snakes detected during nights at a predominately Lower Colorado River Valley subdivision community south of Phoenix and at a primarily Arizona Upland subdivision community west of Phoenix. The snake communities were largely concordant both in diversity and abundance of species at these Sonoran Desert sites: four species (Crotalus cerastes, C. atrox, C. scutulatus, and Rhinocheilus lecontei) accounted for 67-70% of all individuals at the two sites. The most common species exhibited similar distributions at both of the sites with respect to habitat adjacent to the roadway. Following a dramatic upsurge in traffic volume at both sites in the past decade, the abundance of all snakes declined at one site, and the proportion of dead snakes increased significantly at the other site. Comparison with other road-riding surveys of snake communities in the American Southwest indicates that this technique provides consistent and repeatable results, and that this method suggests similar species numerically dominate snake communities in the Sonoran Desert of Arizona.