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Biology
Completed Project

Depredation Rates of Simulated Turtle Nests by Local Predators in Fence-Constrained Versus Unconstrained Nesting Areas

Dara Davis, Vassar College ’15, Maggie Sowa, Vassar College ’15, Kate Spence, Vassar College ’18 and Prof. Marshall Pregnall 

Listed as a threatened species in the New York State, the Blanding’s turtle, Emydoidea blandingii faces high nest depredation rates from meso-predators including skunks and opossums. Our study population in Lagrangeville, NY primarily inhabits a series of natural and constructed wetlands between Arlington High School (AHS) and Baird State Park. Blanding’s turtles may explore a roughly 1-2 km radius to find suitable nesting areas; however, in our local population the barrier fence between the AHS athletic fields and wetlands, which was constructed to reduce negative interactions between turtles and human activities, severely constrains the space for potential nesting. As a result, turtle- egg predators have a very confined zone within which to forage for eggs, and thus a higher likelihood of encountering a nest. We examined the depredation rates of simulated turtle nests by creating mock nests using quail eggs and shams; these were installed within the fenced-in wetland, outside the fenced area in open meadows, among athletic fields, and in a golf course. Depredation rates of the simulated nests were significantly higher in June compared to July, within the fenced-in areas compared to the unconstrained areas, and in the tilled areas compared to the vegetated areas. Increase in nest distance from the tree line significantly increased time until depredation. Finally, we found no significant difference in depredation rates between experimental nest types (egg versus sham). Our results highlight some confounding consequences resulting from conservation techniques involving constructed, constrained environments; future studies should investigate the effectiveness of turtle conservation strategies specifically in constricted areas.