Snakes and Monocultures: Habitat Selection and Movements of Female Grass Snakes (Natrix Natrix L.) in an Agricultural Landscape

Abstract

We investigated habitat selection and movement patterns of female Grass Snakes (Natrix natrix helvetica) in an agricultural landscape where cropping is the dominant farming practice. The aims were to estimate the relative importance of monoculture as habitat for these snakes and to assess its functional relevance to the snakes. Radiotelemetry was used to measure movements by snakes, and the locations of animals were used as sampling points to examine patterns of habitat use. In the course of the tracking period, all females used monocultures. Because of a combination of suitable basking sites, favorable foraging opportunities, and low pressure from avian predators, monocultures may provide at least temporary advantages over more natural habitats, with a seasonal shift in functional relevance induced by the time of oviposition. Overall, the snakes showed a marked preference for edge habitats, which make up only 7% of the study area. At the microhabitat level, a snakes' probability of occurrence was positively correlated with either percentage cover of perennial layer or distance to cereal crop or with both. Our results clearly demonstrate that monocultures are a component of the habitat of female Grass Snakes during their summer activity period in the study area. However, the marked preference for edge habitats, and the response to particular microhabitat features, emphasizes the importance of a mosaic of habitats and structural heterogeneity of edge habitats for the conservation of this snake population.