Movement of amphibians through agricultural landscapes: The role of habitat on edge permeability

Long-term population persistence depends on successful dispersal and colonization. Within agricultural landscapes, dispersing individuals encounter a variety of edge types. How individuals respond to edges can dictate whether they are permeable to dispersal or act as barriers, with consequences for population connectivity. Using two amphibian species, bullfrogs (Lithobates catesbeianus) and Blanchard's cricket frogs (Acris blanchardi), we conducted two studies to address (1) how abiotic factors influence habitat choice and (2) how habitat choice and movement behavior change based on edge type (edges were between grass-corn, grass-forest, and forest-corn habitats). In the first experiment we found that both species preferred high soil moisture environments during both the day and night; and at night neither species showed a preference for ground or canopy cover. However, during the day bullfrogs had a preference for both ground and canopy cover, while cricket frogs showed no preference. In the second experiment, we found that bullfrogs had no overall preference for one habitat type over another; they were observed traveling along the edge of two habitats. Cricket frogs, on the other hand, showed a strong aversion to forest habitat. We concluded that behavioral responses to different habitats may explain current population trends; movement along edge habitat may allow bullfrogs to readily disperse through altered landscapes whereas cricket frog declines may occur in areas experiencing reforestation due to increased isolation. Conservation practices in agricultural land will likely improve landscape connectivity for these species, especially for declining cricket frog populations.