Upland-wetland linkages: relationship of upland and wetland characteristics with watersnake abundance

Land-use practices surrounding a wetland may be as important for maintaining wildlife populations as the wetland itself. Although imperiled species may appear to be more impacted than ubiquitous species from changes in the landscape surrounding wetlands, studies of common wetland species are useful for conservation because they provide insight into why some species persist despite landscape changes. We therefore investigated the relationship between connectivity, measured as the wetland distance to other wetlands; connectivity quality, implied by wetland distance to roads and forest area within 30, 125, 250, 500 and 1000 m buffer zones around the wetland; and patch size as indicated by wetland size with northern watersnake Nerodia sipedon sipedon abundance. Our results suggest that both upland and wetland characteristics influence the abundance of N. s. sipedon, as wetland size and wetland connectivity to other wetlands were significantly associated with abundance. Abundance was positively correlated with increasing wetland size and wetland connectivity. We were not able to find a significant relationship between abundance and connectivity quality, and wetland distance to road or forest area within 30, 125, 250, 500 and 1000 m buffer zones. We conclude that wetland conservation should focus on wetland complexes as well as individual wetlands. In addition, common wetland species such as the northern watersnake do not appear to be negatively impacted by modifications to nearby terrestrial habitats, such as deforestation and roads, and may benefit from the creation of larger, permanent wetlands.