Effects of Roads on the Structure of Freshwater Turtle Populations

Abstract

Road mortality has the potential to alter the structure of turtle populations because turtle populations are highly sensitive to additive sources of adult mortality. To address the issue, we captured painted turtles ( Chrysemys picta; n = 174) and snapping turtles ( Chelydra serpentina; n = 56) in 18 wetlands surrounded by low road density (≤1.5 km roads/km 2 of landscape) and 17 wetlands surrounded by high road density (>1.5 km/km 2 ) in central New York in 2002. High road density was associated with male-biased sex ratios in painted turtles (74% vs. 54% males; p = 0.01) and snapping turtles (95% vs. 74% males; p = 0.08), whereas turtle morphology and abundance were not associated with road density. Disproportionate road mortality of females on nesting migrations is the most likely cause of skewed sex ratios. Efectos de Caminos sobre la Estructura de Poblaciones de Tortugas DulceaucícolasResumen: La mortalidad en caminos tiene el potencial de alterar a las poblaciones de tortugas porque son relativamente sensibles a causas aditivas de mortalidad de adultos. Para abordar este tema, en 2002 capturamos Chrysemys picta (n = 174) y Chelydra serpentina (n = 56) en 18 humedales con baja densidad de caminos (≤1.5 km caminos/km 2 de paisaje) y en 17 humedales con alta densidad de caminos (>1.5 km caminos/km 2 de paisaje) en New York central. La densidad alta de caminos se asoció con proporciones de sexo sesgadas hacia machos en Chrysemys picta (74% vs. 54% machos; p = 0.01) y en Chelydra serpentina (95% vs. 74% machos; p = 0.08), mientras que la morfología y abundancia de tortugas no estuvieron asociadas con la densidad de caminos. La excesiva mortalidad de hembras en migración reproductiva es la causa más probable del sesgo en las proporciones de sexo.Palabras Clave: Chelydra serpentina, Chrysemys picta, carreteras, mortalidad en caminos, proporción de sexos, tortugas

Movement and habitat use of the snapping turtle in an urban landscape

“…While T. scripta and G. geographica had a positive association with commercial areas which are tied to high vehicle density, owing to the increased availability of basking sites (Peterman and Ryan 2009;Ryan et al 2008), C. serpentina did not. In many previous studies, vehicular-based mortality rates for snapping turtles were found to be extremely high (Haxton 2000;Pettit et al 1995;Rizkalla and Swihart 2006), and vehicular mortality has been shown to adversely affect the sex ratio of turtle populations (Gibbs and Steen 2005;Steen and Gibbs 2004). Our results showed habitat use of C. serpentina negatively associated with commercial and residential areas.…”

“…1; for more details regarding the study site, please see Conner et al 2005;Peterman and Ryan 2009;Ryan et al 2008and 2004 C. serpentina adults (12 female, 11 male; Table 1) were radiotracked through the majority of the active season (roughly 15 May through 30 September) and selectively during the winters to understand movement patterns and habitat use. Turtles were collected using baited 0.76-m hoop traps (Conner et al 2005).…”

“…Extensive nesting migrations and overland movements between wetlands in response to environmental extremes, such as drought, have been reported for C. serpentina across its range (Obbard and Brooks 1980;Steen et al 2010). While recent work suggests that phenomena associated with urbanization, such as road mortality, can impact population demographics of C. serpentina (Steen and Gibbs 2004), there is a lack of understanding of their spatial ecology in urban areas where these threats are the greatest. Conner et al (2005) reported that C. serpentina is a prominent member of the turtle assemblage in the Central Canal.…”

“…However, the potential negative impacts of urbanization on the biology and population structure of turtle communities can be profound and diverse (Marchand and Litvaitis 2004a;Ryan et al 2008;Steen and Gibbs 2004). Altered features common to urban areas such as roads, increased land use, and subsidized predators are known to impact the distribution, population demographics, and spatial ecology of turtle communities (Marchand and Litvaitis 2004b;Steen and Gibbs 2004;Sterrett et al 2011). Previously, we have shown that the distribution of upland habitats surrounding a highly urbanized wetland habitat in Indianapolis, Indiana, USA influences the distribution of red-eared sliders (Trachemys scripta) and map turtles (Graptemys geographica) during both the active season and during hibernation (Ryan et al 2008).…”

Terrestrial habitat requirements of nesting freshwater turtles

“…Development of terrestrial areas could impact turtles in several ways. For example, vehicle-induced road mortality is of conservation concern to turtles (e.g., Aresco, 2005a;Gibbs and Steen, 2005;Steen and Gibbs, 2004). Where roads intersect turtle migration routes and result in high mortality, barrier walls in association with culverts facilitate safe turtle movements (Aresco, 2005b;Dodd et al, 2004).…”