Demographic and reproductive traits of blanding's turtles, Emydoidea blandingii, at the western edge of the species' range

Conspecific turtle populations typically exhibit variation in demographic and reproductive traits such as adult size, growth rate, sex ratio, and clutch size. Variation in these traits has been previously correlated to variation in local environmental conditions, latitude, and habitats. Given that some turtle species have large geographic ranges and occur in a variety of habitats, it is imperative to determine how traits differ throughout the species' range. Towards this end, we examined demographic and reproductive traits of Blanding's Turtles (Emydoidea blandingii) in Grant County, Nebraska over the span of six years. The population's sex ratio was female biased (0.7:1.0, M:F) and skewed towards large, adult turtles (5:1, adult:juvenile). The analysis of adult survivorship suggests that female turtles (59% annual survivorship) may be experiencing greater mortality rates compared to males (90% annual survivorship), possibly due to road mortality. Unlike all previous reports, analyses of reproductive parameters indicate that turtles in the western Nebraska population do not increase clutch size with body size. Rather, egg size increases as body size increases, which may help reduce desiccation rates of the eggs in an arid environment. Optimal egg size may not be reached due to pelvic width constraints of females. Comparisons of our findings with those of other Blanding's Turtle studies are discussed.