Bog Turtle (Glyptemys muhlenbergii) Nesting Ecology and the Efficacy of Predator Excluders in New York

Nest predation is a conservation concern for species with low reproductive output, such as Glyptemys muhlenbergii (Bog Turtle). Over 4 years and across 9 sites in New York, we monitored 77 Bog Turtle nests and examined clutch size (n = 77; 1–5 eggs; mean = 3.3 eggs ± 0.92 S.D.), incubation periods (n = 27; 67–89 days; mean = 79.7 days ± 5.78) and temperatures, and the effectiveness of predator excluders. We compared nest-predation rates with (n = 53) and without (n = 24) predator excluders and assessed the effects of predator excluders on hatching rates and incubation timing. On average, protected nests lost 1.04 fewer eggs to predation than nests without predator excluders, and the predation rate (loss of 1 or more eggs) was 25% lower for protected nests (38%) than for unprotected nests (63%). However, the failure rate for eggs surviving predation was marginally higher for protected nests versus unprotected nests, and the number of viable hatchlings produced per nest was not statistically different between protected versus unprotected nests. Overall, our results underscore the need to monitor hatching rates in addition to predation rates when evaluating the success of predator-exclusion devices for turtle conservation.