UTILIZING A MULTI-TECHNIQUE, MULTI-TAXA APPROACH TO MONITORING WILDLIFE PASSAGEWAYS IN SOUTHERN VERMONT

Abstract

Roadways affect wildlife habitat disproportionate to the area of land they occupy, impacting wildlife through the loss and fragmentation of habitat, road mortality and disruption of movement. A variety of strategies have been used with mixed success to mitigate the impacts of transportation systems on wildlife. Through 2008, nearly 700 terrestrial and 10,700 aquatic crossing structures have been identified throughout North America but only a small portion of these crossings had monitoring incorporated into their project design. Building on prior studies, this project takes a broad, multi-taxa approach to monitoring crossing structures on a newly constructed highway (the Bennington Bypass) in southern Vermont. We used a variety of techniques to assess movements of an array of species at two passage structures associated with the highway as well as in the surrounding landscape. Techniques used in our study include: track beds/plates, remote camera sensing, small mammal trapping, snow-tracking and road kill surveys. Our data suggest that the concurrent use of track beds and camera traps provide excellent tools for determining an index of passage use but are limited in their ability to monitor individual use of structures. Six hundred and ninety small mammals were ear tagged over two field seasons, with 15 individuals successfully moving through the crossing structures and one individual crossing the road, suggesting that the road serves as a barrier to movement and the structures may only minimally mitigate those effects. Snow-tracking is an excellent tool for detecting movement of animals in and around structures but is limited seasonally and similar to track beds/cameras, cannot discern individuals. Road kill surveys showed a minimal number of deer hit by vehicles but revealed high mortality on amphibians, reinforcing our suggestion that monitoring should take a multi-taxa approach. By monitoring a wide variety of animal movements rather than focusing exclusively on the use of passages by wildlife, we believe we can more accurately assess the effectiveness of the mitigation structures.