Occupancy of freshwater turtles across a gradient of altered landscapes

Abstract

Turtles are one of the most threatened groups of vertebrates worldwide. In the northeastern United States, a legacy of centuries of dramatic landscape alteration has affected freshwater turtle populations, but the relationships between the current landscape and distributions and abundances of freshwater turtles remain poorly understood. We used a stratified random approach to select 88 small, isolated wetlands across a gradient of forest cover throughout Rhode Island, USA, and systematically sampled freshwater turtles in these wetlands. We report estimates of relative abundance and used a canonical correspondence analysis to investigate relationships between species relative abundance and environmental covariates. We also investigated which environmental covariates affect the occurrence and detection probabilities of each species. Eastern painted turtles (Chrysemys picta picta) and common snapping turtles (Chelydra serpentina) were widespread (occurring in 83% and 63% of wetlands, respectively) and relatively abundant. Spotted turtles (Clemmys guttata) were far less common, occurring in 8% of wetlands, and exhibited a positive association with shallow wetlands surrounded by forest. Non-native red-eared sliders (Trachemys scripta elegans) occurred in 10% of wetlands and exhibited a positive association with road density, likely reflecting a positive relationship between slider occurrence and human population density. Identifying landscape-scale habitat features that are associated with the occurrence of sensitive species can improve the ability of biologists to identify and protect turtle populations. Ó 2018 The Wildlife Society.

A Comparison of the Population Genetic Structure and Diversity between a Common (Chrysemys p. picta) and an Endangered (Clemmys guttata) Freshwater Turtle

“…From 2013-2015, small (0.1-1.8 ha), hydrologically isolated (i.e., discrete, non-riparian) wetlands throughout the state were randomly selected across a gradient of forest cover for a mark-recapture study focusing on occupancy and demography [25] (see reference for additional information on site selection and sampling methodology). Tissue collection for genetic analysis took place concurrently at a subset of these wetlands.…”

“…Under both scenarios where K ≥ 4, these sites contained the highest probabilities of belonging to the distinct clusters (Figure 2A-B). Interestingly, these three sites are all manmade or heavily modified [25]. Sites 12 and 15 were both constructed between 1972 and 1976, whereas site 21 predates the earliest available aerial imagery but is clearly a pool that formed when a former stream was bisected by a road.…”

Influence of landscape condition on relative abundance and body condition of two generalist freshwater turtle species

“…It is interesting that individual‐level responses to ecological integrity differed between these two generalist turtle species, as both species are prevalent in wetlands that span a wide range of environmental conditions (Brown et al., 2012; Buchanan et al., 2019). Wetlands associated with anthropogenic landscapes generally differ from those in more natural systems.…”

“…Created wetlands (e.g., farm ponds and mitigation wetlands) also tend to be deeper than natural wetlands (Cole & Brooks, 2000; Cole et al., 2006; Gamble & Mitsch, 2009). These wetland‐specific characteristics likely interact with the surrounding landscape condition to influence habitat quality for the two species (Buchanan et al., 2019; Cosentino et al., 2010; Ryan et al., 2008). While our study was not designed to control for wetland characteristics, we encourage future studies to explore interactions between landscape integrity and species‐specific wetland habitat quality.…”

“…Both species generally prefer shallow lentic freshwater habitats containing a soft mucky bottom with abundant aquatic plants (DonnerWright et al., 1999; Janzen et al., 1992; Morreale & Gibbons, 1986). Both species are also commonly found in wetlands associated with anthropogenic land use, such as agricultural farm ponds and urban retention ponds (Buchanan et al., 2019; Stone et al., 2005). Further, many studies have indicated that densities of painted turtles and red‐eared sliders in anthropogenic wetlands are much higher than other turtle species occupying the same wetlands (Brown, Farallo, et al., 2011; Failey et al., 2007; Glorioso et al., 2010).…”