Suggested Citation:
Shilling, Fraser M., Paul Haverkamp, Maria Santos, Susan Ustin (2012) Limited Wildlife Diversity at Highway Right-of-Way Crossings. Institute of Transportation Studies, University of California, Davis, Research Report UCD-ITS-RR-12-20

Understanding the impacts of transportation systems and related disturbances on wildlife movement is critical to mitigating these impacts. To understand these impacts, we investigated the occurrence and movement of terrestrial wildlife in the vicinity of a major highway in the Sierra Nevada, while controlling for other environmental and disturbance gradients. Road and highway systems impact the surrounding environment, changing flows, ecosystem processes, species relationships, landscape patterns, and other ecological attributes (Wheeler et al., 2005; Fahrig and Rytwinski, 2009).Roads and highways pose barriers to wildlife dispersal and migration through aversion effects (“habitat alienation”, e.g., Mac et al., 1996), direct mortality from traffic (Madsen, 1996; Putman, 1997; Rubin et al., 1998), and traffic noise-induced effects (Reijnen et al., 1997; Gill et al., 1996). The combination of disturbed edge and physical barrier can reduce the effective area for species that depend on intact habitat in the interior of patches (Boarman and Sazaki, 2006) and that migrate among patches. Since roads are often accompanied by other development activities, there may be additional fragmentation effects beyond just the linear extent of the road (Theobald et al., 1997). Mitigation efforts for these fragmentation effects have been made in particular geographic locations by installing underpasses and overpasses intended for use by large mammals (e.g., Clevenger and Waltho, 2000). However, the effectiveness of these purpose-built structures, or existing drainage (culvert) and traffic structures for passing wildlife is seldom well-studied.