Road ecology and microhabitat assessment of black hills red-bellied snakes and smooth greensnakes in an isolated mountain range

Understanding species habitat use and population threats is important to inform effective conservation management. In 2016, we conducted a road ecology and microhabitat project for Black Hills Red-bellied Snakes (Storeria occipitomaculata pahasapae) and Smooth Greensnakes (Opheodrys vernalis) in the northern Black Hills of South Dakota. Both species are of conservation importance. We surveyed more than 1,700 km of rural, unpaved roads and analyzed data for 75 snakes. Road-adjacent microhabitats were similar where either species was found, suggesting syntopy. Areas with rocky substrates and denser, taller herbaceous vegetation were seasonally favored by both species: flat mesic meadows were indicative of active season habitat and steep south/southwest-facing slopes were typical of overwintering habitat. We found that temporal factors (e.g., coinciding with seasonal ingress) best predicted snake activity on roads, especially for certain areas. High rates of road mortality (78.6%) throughout the study area, however, are concerning. Because roads bisect important seasonal habitat features, and both species are small and relatively non-vagile, they are likely susceptible to vehicle strikes, even at relatively low traffic volumes along local roads. Road mortality is likely a significant driver of population decline. Because of their overlap in natural history, likelihood of road mortality, and similarities in habitat use, we recommend wildlife managers consider umbrella-concept conservation strategies, especially in important seasonal habitats and migration corridors.