Nest predation is a major concern for the federally threatened Bog Turtle (Glyptemys muhlenbergii), and wire-mesh predator excluders are a common conservation tool — but caging a nest can also alter its temperature and incubation conditions in ways that might backfire. Over 4 years across 9 New York wetland sites, this study monitored 77 Bog Turtle nests, comparing predation rates and hatching outcomes between nests with and without predator excluders.
Excluders worked as intended on the predation side: protected nests lost about 1 fewer egg to predators on average, and the overall nest-predation rate was 25 percentage points lower than for unprotected nests. But protected nests also had a notably higher rate of egg failure among the eggs that survived predation — enough to erase most of the predation-reduction benefit, leaving the number of turtles that actually hatched statistically indistinguishable between protected and unprotected nests. The result is a cautionary tale for turtle conservation: a device that clearly works against predators isn’t automatically a net win for recruitment, and effectiveness has to be judged by hatching success, not predation rates alone.
Citation: Macey, S.K., Myers, A.T., Tesauro, J., Feil, A., Polanco, K., Clark, J.A., Shoemaker, K.T. 2024. Bog Turtle (Glyptemys muhlenbergii) Nesting Ecology and the Efficacy of Predator Excluders in New York. Northeastern Naturalist 31(sp12):G117-G137. https://doi.org/10.1656/045.031.s1232