Wildlife-Vehicle Collisions – Effective Mitigation Strategies USING SPECIALISED TUNNELS TO REDUCE HIGHWAY MORTALITY OF AMPHIBIANS

Previous studies identified roads as a source of habitat fragmentation and mortality for amphibians in Waterton Lakes National Park, Alberta, Canada, thus reducing the effects of roads became an important management issue. Vehicle traffic resulted in appreciable mortality of the Linnet Lake population of long-toed salamanders when adult and juvenile animals moved between this breeding site and terrestrial habitats. Tiger salamanders, western toads and red-sided garter snakes have also been killed by vehicles at this location. In spring 2008, drift fences and pitfall traps were installed for about 500 m along both sides of the Entrance Road that runs parallel to Linnet Lake to intercept and capture migrating amphibians attempting to cross the road. Road surveys were conducted daily before dawn for animals that evaded the fencing. Captured long-toed salamanders were marked with visible implant elastomer so a population estimate could be derived using a mark-recapture method and so that individual movement could be detected. Four specialised tunnels (AT500, built by ACO Wildlife) were installed in summer 2008 to allow long-toed salamanders and other small animals to cross safely under the road. Each tunnel is a ―box culvert‖ 600 mm wide x 520 mm high. Each 1-m pre-cast segment was made of polymer concrete with slots that allowed air, moisture and light into the tunnel, creating a hospitable environment for amphibians. Segments were fitted together to span the width of the road (12 m), and set in concrete. Distances between tunnels varied from 80 m to 110 m. Installation took about two weeks; half of each tunnel was installed, traffic re-routed until the concrete set, then the other half was installed. We installed remotely-triggered cameras at the roof of each tunnel entrance to record animal movements. Cameras were set to detect motion and also to record images at fixed time intervals. We continued monitoring the population, movement patterns, and use of tunnels in 2009. In 2008 we captured 445 long-toed salamanders; the population was estimated at 1492 ± 214 adults. We also captured 15 tiger salamanders and 21 western toads. Two percent of long-toed salamanders (i.e., 10 of 445 individuals) travelling to or from Linnet Lake died on the road in 2008. Cameras photographed long-toed and tiger salamanders, western toads, and a variety of small mammals using the tunnels from 28 August to November 2008. Relatively few amphibians used the tunnels in 2008, because drift fences were still directing animals into the pitfall traps, and trapped animals were transported across the road. In spring 2009, fences were re-constructed to direct animals to the mouth of the tunnels, with one pitfall trap at the end of each tunnel. To 9 June 2009, 107 long-toed salamanders, moving both to and from the lake, have successfully navigated through the tunnels. Most images of salamanders have been captured using fixed-time monitoring rather than motion detection. Our preliminary observations suggest that installation of drift fences effectively reduced road mortality and that the installation of road tunnels provides an effective and safe route of travel for a diversity of animals including long-toed salamanders. Monitoring via trapping and cameras promises to produce a meaningful assessment of the use of tunnels by amphibians and their effectiveness in reducing road mortality in Waterton Lakes National Park.