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Bog Turtle (Glyptemys muhlenbergii) Population Dynamics and Response to Habitat Management in Massachusetts
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Abstract
The Bog Turtle (Glyptemys muhlenbergii) is a federally threatened species that occupies isolated pockets of open-canopy fens. This long-lived species is susceptible to habitat loss and degradation; thus, the conservation of known populations and management of their habitat is critical to the species’ survival. Long-term (multi-decadal) assessment is important for determining population trends and responses to ongoing habitat management. I assessed population demographics (abundance, survival) and spatial distribution (home range) of two Bog Turtle populations in Massachusetts that have been managed since the late 1990s by treating invasive species, thinning woody vegetation, and mitigating flooding. The results of this study were compared to two previous studies conducted in 1994–1997 and 2005–2009 to evaluate the response to habitat management. Estimates of adult population abundance increased from the first study period (Site 1 X̅= 37.3 ± 10.4, Site 2 X̅= 36.2 ± 3.2) to the last study period (Site 1 X̅= 65.1 ± 17.9, Site 2 X̅= 42.5 ± 10.9) across both sites. Estimates of annual survival across all study periods remained above 90% at Site 1 and were 100% for two years at Site 2. I constructed 95% minimum convex polygon (MCP) and 95% kernel density estimation (KDE) home ranges for 71 turtles. At Site 1 there was no significant influence of the study period on home range estimates. The increase in abundance estimates, high survival, and stable home range sizes at Site 1 suggest that ongoing management has maintained quality habitat. At Site 2, the average home range size decreased by approximately half after the first study period in response to flooding but increased in the current study. Fluctuations in population abundance, and home range size at Site 2 throughout the study period reflect the cycles of habitat degradation and habitat management. My results indicate that habitat management efforts implemented since the late 1990s have provided quality habitat for the two Bog Turtle populations in Massachusetts while also mitigating long-term negative impacts on the populations. This further supports the need for long-term analysis of Bog Turtle populations, especially at sites where active habitat management is occurring.
Type
thesis
Date
2023-09