Wawona Road Wildlife Crossing Structures for Pacific Fishers

This project is taking proactive measures to reduce Pacific fisher mortalities from vehicle collisions (road-kill) along Wawona Road by building innovative wildlife crossing structures that would facilitate safe animal movement. Pacific fishers are a candidate for listing under the federal Endangered Species Act (ESA), and recent camera research in the park indicates that a very small population exists in the southern portion of Yosemite, including the Mariposa Grove of Giant Sequoias, along Wawona Road near Chinquapin, and near Wawona. Fishers inhabiting this area of the southern Sierra Nevada are at the northernmost tip of their current range and must be able to safely cross the road on a regular basis if their population is to recover by expanding northward into historically occupied areas. Since 2007, six fisher road-kill mortalities have been recorded along Wawona Road, which bisects a narrow corridor of highly suitable fisher habitat. Within this same time period, three additional fishers have been killed by vehicles just south of the park on Highway 41 in Sierra National Forest. Wildlife crossing structures would provide a safer option for animals inhabiting this narrow corridor of suitable habitat to cross the road, and may help give this small fisher population its best chance at survival and potential recovery.

Using camera equipment from the 2009-2011 Yosemite Conservancy funded fisher study, the park has been actively monitoring several drainages with existing culverts along Wawona Road since fall 2011. These drainages act as wildlife movement corridors and serve as potential locations for wildlife crossing structures. Current camera work has shown fishers to be actively using three drainages along Wawona Road. Fishers are especially vulnerable to being hit by vehicles while crossing the road during denning season (March 1 - June 30) when females are searching for food and males are traveling large distances to locate potential mates.

This project would mitigate the road-kill threat by (1) modifying three existing culverts along Wawona Road to include a shelf-style wildlife crossing structure that small to medium sized mammals could use to safely cross underneath the road; and (2) include pre- and post-construction monitoring with remote, motion-sensing cameras to determine what wildlife species are using the drainages as movement corridors. This project is a diverse partnership with Defenders of Wildlife, the U.S. Forest Service, U.C. Berkeley Sierra Nevada Adaptive Management Project (SNAMP), Fisher Study, and the National Park Service. The timing of this project is important as the Pacific fisher's status will be reviewed for listing under the ESA in 2014.