Bog Turtle Demographics within the Southern Population
Turtles are among the most vulnerable vertebrate group to declines, extirpations, and extinctions, especially those species with specific habitat requirements. The Bog Turtle (Glyptemys muhlenbergii) is listed as federally Threatened in the United States, but the southern population of the species does not receive full habitat protection under the Endangered Species Act. To understand Bog Turtle demographics within the southern population, we applied Cormack-Jolly-Seber and multistate models in program MARK and calculated annual adult, sex-specific, and juvenile survival for intensively sampled (19–180 sampling days) Bog Turtle populations in North Carolina. The most parsimonious model indicated that adult survival remained constant over time for all populations, but was relatively low when compared to other species of turtles. Adult survival estimates varied between 0.86 and 0.94 among the sites, all below the 0.96 adult survival estimate documented for northern Bog Turtle populations. To evaluate variation in juvenile survival, we focused on three populations: the two largest known populations and an intensely studied, but critically declining population. The two largest populations had a greater proportion of juveniles than other populations and higher juvenile survival (0.68 and 0.67) than the declining population (0.50). Thus, conservation efforts targeting juvenile survival and recruitment, such as nest protection and habitat enhancement, are important to ensure population stability. Furthermore, our estimates of adult and juvenile survival indicate that North Carolina populations are likely declining and without stronger protection measures, local and regional extirpations of the species may occur.

The number of Bog Turtles captured each year, both adults (light gray) and juveniles (dark gray), as well as the number of sampling events per year (solid line with filled circles) at sites A, B, and E in North Carolina, USA.

(A) The sex ratio, the proportion of male and female Bog Turtles represented in each population A–K in North Carolina, USA. (B) Age structure and proportion of Bog Turtles first captured as juveniles (age 1–6) or adults (age 7+) at sites A–K in North Carolina, USA. The sites are ordered by number of marked turtles, from greatest to least. All captures were used and thus the sex and age structures may not reflect the current population.

Adult survival (age 7+) of eight Bog Turtle populations in North Carolina, USA. The sites are ordered by number of marked turtles, from greatest to least. The height of the bars indicates the estimated annual survival probability (Φ), the data labels are the adult survival point estimates, and error bars are 95% confidence intervals.

Juvenile survival (age 1–6) of three Bog Turtle populations in North Carolina, USA. The height of the bars indicates the estimated annual survival probability (Φ), and the error bars are 95% confidence intervals. Note that juvenile survival was estimated from multistate models for each site. Additionally, juvenile survival for Site E was estimated over the time period corresponding to the greatest number of juvenile captures (1992–1998).
Contributor Notes
Associate Editor: J. D. Litzgus.