Summary
Urbanisation and agriculture are paradigmatic cases of habitat loss, degradation, and fragmentation that imperil wildlife. Anthropogenic landscape modifications can harm species such as freshwater turtles that rely on both aquatic and surrounding terrestrial habitats to survive and reproduce. We tested the hypothesis that the local abundance of painted turtles (Chrysemys picta) in wetlands depends on the composition of the surrounding landscape. We predicted that there would be fewer turtles in wetlands in more modified landscapes (i.e., urban and agricultural) with higher road densities. From repeated visual surveys of 34 wetlands around Ottawa, Canada, we found that there were more painted turtles in wetlands that were larger and surrounded by more forest. Therefore, proper management of forested lands and green areas in urban landscapes are needed to protect turtles cohabiting with humans.
Methodology
We assessed painted turtle abundance in 34 wetlands in Ottawa, Canada. We selected wetlands to span a gradient of urbanisation. To minimise potential dispersion between sites and spatial auto-correlation (Stokeld et al., 2014), we selected wetlands that were at least 1.5 km apart. This distance was chosen because it is beyond the dispersal abilities of most painted turtles (Christens and Bider, 1987; Marchand and Litvaitis, 2004; Steen and Gibbs, 2004; Patrick and Gibbs, 2010). Importantly, we did not select wetlands on the basis of their expected suitability for turtles. Wetlands varied in size, ranging from 0.12 ha to 19.57 ha, with a mean area of 4.12 ha.