Ecology and status of the bog turtle (Clemmys muhlenbergii) in New England

The federal-listed bog turtle (Clemmys muhlenbergii) is the smallest and rarest freshwater turtle species in North America. I studied bog turtles in New England from 1994–1997, examining habitat use and seasonal movements, breeding ecology, demographic characteristics and population viability. I made 1,553 captures, marked 75 adults and radiotracked 50 bog turtles. Home range sizes (0.06–2.79 ha) were similar to other studies; there were no detectable differences between sexes, although males and females used different habitats among seasons. Size of female at sexual maturity (plastral length = 74 mm) was based on reproduction instead of secondary sex characteristics. Clutch size ranged from 2–6 eggs (x¯ = 3.5), with individual variation among years. Incubation (74–103 days) was longer for Massachusetts sites compared to southern nests, and both hatchlings and adults were smaller in body size compared to southern populations. I modeled a stable population with estimated survival rates of 0.32 for hatchlings, 0.97 for adult females, size and age at sexual maturity of PL = 74 mm and 12 y, respectively, and a derived juvenile survival rate of 0.83 (assuming λ = 1.00). The cooler climate and shorter breeding season may place additional constraints on northern populations of bog turtles. These environmental factors may result in slower growth rates, delayed sexual maturation, smaller adult body sizes, iteroparity, and lower nest temperatures resulting in longer incubations of fewer and smaller hatchlings than those in the south. While biologists cannot manage for climate, we can implement protection of this threatened species by identifying and protecting important habitats for hibernation and nesting, preventing hydrologic changes to the system, maintaining open canopy cover, and reducing direct human and animal impacts on adults through monitoring and active management strategies. I suggest the best strategies for bog turtle conservation involve identification and protection of habitats occupied by reproducing populations rather than captive breeding and translocation