Does Landscape Composition Affect Wetland Occupancy by Blanding's Turtles (Emydoidea blandingii) in the National Capital Region?

Abstract

Within a landscape, a species’ occurrence is dictated by the availability of suitable habitat and resources needed for survival; however, occurrence is not only affected by the characteristics of occupied sites, but also by the characteristics of the surrounding landscape. The endangered Blanding’s turtle (Emydoidea blandingii), a semi-aquatic freshwater turtle, occupies a wide range of wetlands and landscapes in southeastern Canada and the northeastern United States. While the effects of habitat characteristics on wetland occupancy by Blanding’s turtles have been documented, here I explore whether the probability of wetland occupancy by Blanding’s turtles is affected by the surrounding landscape. I used visual surveys, environmental DNA, and atlas data to document the presence of Blanding’s turtles. I then used boosted regression tree modelling to determine how landscape composition explains wetland occupancy. Forest cover around the surveyed wetlands was the strongest positive driver of turtle occupancy while anthropogenic land cover was the strongest negative driver of turtle occupancy. Generally, human disturbances in a landscape lowered the probability of occupancy. Overall, I determined that wetland occupancy by Blanding’s turtles is affected by landscape composition and that, therefore, wetland occupancy can successfully be predicted from the composition of the surrounding landscape.