Effect of Landscape Composition on Snake Abundance in Wetlands

Abstract

Habitat loss is driving the biodiversity loss crisis, and agriculture is one of the leading sources. Reptiles are especially sensitive to environmental change, yet are less frequently studied. My study aims to investigate the landscape effect of agriculture on garter snake (Thamnophis sirtalis) and redbelly snake (Storeria occipitomaculata) abundance in wetlands in Eastern Ontario and Southern Québec, Canada. I expected snakes to be less abundant at wetland sites with more agricultural land in the surrounding landscape. I also expected snakes to be smaller on average in wetlands in more agricultural landscapes. I tested this by estimating population abundance in wetlands embedded across a gradient of agricultural and natural landscapes in the Ottawa/Gatineau area. Sites were surveyed once a week from May to September in 2023 and 2024, and any snakes captured were counted, marked, and measured. The number of garter snakes and redbelly snakes caught did not differ significantly across sites with increasing agricultural land cover in the surrounding landscape, according to the final model; however, an alternative model indicated significantly fewer snakes in wetlands with more surrounding agriculture. Snake size did not significantly differ across the agricultural gradient.