Ecological Aspects of a Wood Turtle, <em>Glyptemys insculpta</em>, Population at the Northern Limit of its Range in Québec

Abstract

As part of a conservation research initiative, a population of Wood Turtles (Glyptemys insculpta) at the northern limit of its range was studied to ascertain characteristics of its demographics, morphometrics, density, mortality, feeding, and mating activities. Turtles were captured and marked during the activity period in 1996 and 1997. In addition, 20 individuals were radio-tracked weekly. A total of 188 turtles was captured and the size of the population in the study area was estimated at 238 turtles. The estimated population density based on this calculation is 0.44 turtles/ha. This is less than other studies indicating that population densities are greater in southern populations. Turtles from this population were large (carapace length of males=214.5 ± 4.21 mm, females=201.1 ± 10.88 mm) which supports the hypothesis that turtle size is negatively correlated with number of frost free days. The sex ratio was not significantly different from 1:1. Juvenile turtles accounted for 31.4% of the population. Observations of feeding habits support the claim that Wood Turtles are opportunistic omnivores. Of the 35 mating or courtship events observed, 77 % occurred in the fall and half of them between 11:00 and 13:00. Although limb and tail injuries and parasites were observed on many turtles, no dead turtles were observed. This last result, combined with the high rate of recruitment and even sex ratio suggests that this population is stable, making it an ideal population with which to make comparisons with other studies in areas where the species could be in decline.

Conservation genetics of a peripherally isolated population of the wood turtle (Glyptemys insculpta) in Iowa

“…At the northern limits of the species distribution in Ontario, census population size is approximately 238 turtles (Walde et al 2003). Our estimate of census population size in Iowa (77 turtles) is one of the lowest reported for a G. insculpta population to date, similar to that estimated for the species in Quebec (66 turtles; Daigle 1997).…”

“…Wood turtle population size is suppressed by habitat fragmentation due to agriculture and urban development, injury from agricultural practices and vehicle traffic, and collection for the pet trade Bider 1998, 2007;Levell 2000;Gibbs and Shriver 2002;Walde et al 2003;Ernst and Lovich 2009). Agricultural practices are associated with reduced juvenile prevalence (Saumure and Bider 1998) and appear, in Iowa, to benefit raccoon and skunk populations (Kuehl and Clark 2002), which are major predators of wood turtle eggs and juveniles (Harding 2008;Ernst and Lovich 2009).…”

An 18-Year Mark–Recapture Study of Wood Turtles (Glyptemys insculpta) in Michigan

“…Our population estimates (20-32 turtles km -1 ), however, are well within the range of other studies that have reported population estimates per river km (Walde et al, 2003;Daigle and Jutras, 2005;Brown et al, 2017; Table 1). Willoughby et al (2013) reported evidence of a historical decline in this population of Wood Turtles using genetic data and a coalescent theory model (MSVar).…”

Sexual Dimorphism in the Greek Tortoise: A Test of the Body Shape Hypothesis

“…However, studies on other aquatic species, which may be expected to show the same patterns of size and shape dimorphism as C. picta, have found that females are more likely to be killed by predators than males (Emmons, 1989;Gibbons and Lovich, 1990;Shealy, 1976), although these are also species in which females probably encounter more predators than males. In addition, previous studies have also found that female turtles show proportionally more injuries than males in some species, including G. insculpta (Ernst, 1976;Walde et al, 2003). These studies may suggest that females encounter more predators than males, or they may actually provide support for the idea that female turtles are better able to withstand predator attacks-the lower incidence of injuries among males may indicate that their encounters with predators more often end in death rather than injury.…”