Snakes on the plains: The impacts of habitat structure on snake communities in Illinois grasslands

Snakes are an integral component of grassland ecosystems, though their occurrence in high densities is often discouraged because of their role as nest predators of declining grassland birds. The effects of habitat structure on snake communities in grasslands remains poorly understood, hindering management efforts. We used 3 years of data from a series of restored grasslands in southern Illinois to examine how habitat structure across 3 spatial scales (local, patch, landscape) affected snake relative abundance, diversity, and species-specific occupancy in grasslands. We found that snake community metrics were strongly and positively related to an increase in woody plant cover at the local (within-patch) scale. Snake relative abundance was also positively related to an increase in grass cover and a decrease in forb cover, though our occupancy results suggest that this was primarily driven by an increase in black kingsnakes (Lampropeltis nigra). At the patch scale, relative abundance and diversity of snakes were both positively related to the proportion of patch edge composed of roads. Habitat structure at the landscape scale had the smallest impact on snakes in this study, though the proportion of trees in the landscape was positively related to snake diversity. We suggest that managers and conservationists interested in manipulating snake abundance in grasslands focus on within-patch vegetation structure and composition. Decreasing woody cover in grasslands, or increasing the ratio of forbs to grasses, may reduce the presence of snakes, while maintaining a woody component could encourage both snake abundance and diversity.