Abstract
Road mortality poses a major threat to turtle populations. Several studies have suggested that the terrestrial movements associated with nesting increase this risk for females. The Ontario Turtle Conservation Centre (OTCC) is home to the Kawartha Turtle Trauma Centre, which admits 900 or more turtles a year, with road injuries the primary cause of admission. We tested the hypothesis that road mortality in turtles is female-biased using data from injured Midland Painted Turtles (Chrysemys picta marginata), Snapping Turtles (Chelydra serpentina), Blanding’s Turtles (Emydoidea blandingii), and Northern Map Turtles (Graptemys geographica) collected over about 126 000 km2 and admitted to OTCC’s hospital from January 2013 to October 2017. There was no difference in the number of male and female admissions of Midland Painted, Blanding’s, or Snapping Turtles (P > 0.05); however, more female Northern Map Turtles than males were admitted (P < 0.001). Admission of female turtles peaked in June during the nesting season, but male admissions were more evenly distributed throughout the season. Our admissions data provide a temporally unbiased and geographically broad snapshot of turtle–vehicle interactions that can directly inform conservation and management policies. Although our data are not equivalent to mortality rates, these results demonstrate that vehicle strikes can have a substantial impact on both female and male turtles.
Highlights
Roads have been called the “sleeping giant” of conservation biology (Forman and Alexander 1998) because of their pervasive negative impact on biodiversity and habitat connectivity
Several studies have tested the hypothesis that female turtles are at higher risk of road mortality during the nesting season because overland movements required to find a suitable nest site may increase females’ probability of contact with roads (Steen and Gibbs 2004; Aresco 2005; Gibbs and Steen 2005; Steen et al 2006; Patrick and Gibbs 2010; Dorland et al 2014)
We tested for significant deviations from an unbiased sex ratio in the admissions data by performing a nonparametric binomial two-sided test based on a one-sample binomial distribution (Wilson and Hardy 2002) with the untested assumption that the populations of turtles in the study area were not sex biased
Summary
Roads have been called the “sleeping giant” of conservation biology (Forman and Alexander 1998) because of their pervasive negative impact on biodiversity and habitat connectivity. Several studies have tested the hypothesis that female turtles are at higher risk of road mortality during the nesting season because overland movements required to find a suitable nest site may increase females’ probability of contact with roads (Steen and Gibbs 2004; Aresco 2005; Gibbs and Steen 2005; Steen et al 2006; Patrick and Gibbs 2010; Dorland et al 2014). If road mortality is female-biased, the adult sex ratios of turtle populations should gradually become male-biased (Steen and Gibbs 2004; Gibbs and Steen 2005; Steen et al 2006; Patrick and Gibbs 2010; Dupuis-Désormeaux et al 2017)
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