Utilization of Stormwater Retention Ponds by Aquatic Turtles in Montgomery County, Virginia

Abstract

Stormwater ponds design to mitigate the negative impacts of runoff from impervious surfaces in urban areas have become common landscape features as they are required by state and local environmental regulations. While some have hypothesized that stormwater ponds may provide habitat for wildlife, few studies have systematically investigated turtle use of stormwater ponds. To investigate stormwater pond use by turtles in western Virginia, I used records of permitted stormwater management structures in the Town of Christiansburg and City of Blacksburg, Virginia, and a stratified random sample design based on hydrology to select 60 (of 324 above ground structures) for sampling of turtle assemblages. I used a combination of visual and trapping surveys to characterize turtle assemblages. I also surveyed design and management variables to identify those conditions that promote use of stormwater ponds by turtles. Visual encounter surveys involving eight or more visits conducted in June and July when air temperatures were between 20oC and 27oC produced high cumulative rates of detection and high detection probabilities during individual surveys, respectively. I found eight taxa utilizing stormwater ponds including two relatively abundant native taxa, the snapping turtle (Chelydra serpentina) and the eastern painted turtle (Chrysemys picta picta), and one non-native taxa, the red-eared slider (Trychemys scripta elegans). The occurrence of turtles was associated with larger ponds with permanent or near permanent hydrology and limited emergent vegetation cover that were located on streams and surrounded by patches of trees and turfgrass cover. These conditions are characteristics of the habitats selected by the native species found in this study, but also indicative of conditions humans may choose when releasing unwanted pet turtles. Therefore, the occurrence of native and non-native taxa may be associated with park-like conditions, but for different reasons, warranting future assessment and monitoring of turtle populations and potential genetic introgression between native and non-native taxa.