Mitigating road mortality of Minnesota's turtles and other small wildlife

Tricia Markle, Minnesota Zoo
Chris Smith (Minnesota Department of Transportation), Peter Leete (Minnesota Department of Transportation), Beth Brown (Minnesota Department of Transportation), and Seth Stapleton (Minnesota Zoo)
Topic Area
Aquatic Species/Ecosystem and Wetland Interactions with Transportation

Minnesota, the land of 10,000 lakes, is a veritable paradise for freshwater turtles. Unfortunately, factors including road mortality have led to population declines in recent decades. In partnership with the Minnesota Department of Transportation, who also wish to improve driver safety, the Minnesota Zoo recently launched a three-year research initiative to quantify road mortality of turtles and other small wildlife. We employ a Before-After-Control-Impact (BACI) design to test the effectiveness of mitigation strategies, including exclusion fencing and signage to increase driver awareness. During 2018, we identified 32 sites (ranging 76m - 625m) across the Twin Cities metropolitan area likely to have high rates of turtle road mortality. Sites were monitored weekly from May through September via foot patrols; all wildlife observed were recorded to establish baseline levels of mortality. We documented >600 dead turtles and >3,000 total animals on survey sites during collection of pre-treatment data. Prior to 2019 monitoring activities, seven sites received one of two treatments: small animal exclusion fencing (n = 4) and seasonal warning signs (n = 3). Exclusion fencing uses off-the-shelf chain-link fencing with "j-hook" end treatments to direct turtles back to wetlands and camera traps will be used to assess their effectiveness. Because habitat connectivity is important for long-term population success, existing culverts at fenced sites will be monitored with camera traps to determine if turtles use these structures to cross under roads. Temporary "Turtle Crossing" road signs offer a less expensive alternative and will be deployed at designated treatment sites during May and June. We hypothesize that fencing will be more effective in reducing mortality of turtles than signs, and we anticipate that these benefits will confer to other wildlife. However, the high costs of fencing will be an important consideration in selecting mitigation measures. We are monitoring treatment and corresponding control sites for two years post-treatment, and will summarize preliminary results from the 2019 research season this summer.

Abstract Keywords
Road mortality