Anthropogenic effects on chronic stress and nest predation patterns in freshwater turtles

Abstract

Human altered landscapes contribute to direct and indirect threats on wildlife populations. Chronically high stress, an indirect threat, has been associated with decreased fitness. I examined chronic stress in Midland Painted Turtles (Chrysemys picta marginata), Snapping Turtles (Chelydra serpentina), and Blanding's Turtles (Emydoidea blandingii) in areas with varying densities of anthropogenic structures in Muskoka,Ontario. Enzyme immunoassays were run, in partnership with Dr. Gabriela Mastromonaco (Toronto Zoo), on turtle claws to obtain concentrations of corticosterone (CORT). Most Snapping Turtles had above-minimum CORT, and male Midland Painted Turtles and Blanding's Turtles had relatively high CORT levels. Anthropogenic density did not seem to affect CORT levels, but more research needs to be done to understand the complex relationships. I also determined the rate and pattern of nest depredation, a direct threat, throughout egg incubation in areas of varying anthropogenic densities. Nest depredation occurred throughout egg incubation and relative nest mesopredator abundance did not differ among sites with varying anthropogenic densities. Contrary to some nest caging protocols, my findings suggest that nest cages should be kept on nests until the turtles hatch and priority should be given to caging nests in low road density areas to help increase population recruitment. Understanding indirect and direct threats to turtles can help inform mitigation strategies to improve their fitness.