Road Ecology Center

Providing mid- and large-sized mammals with safe opportunities to cross roadways can reduce the impacts of highways on wildlife. To maximize effectiveness, this type of mitigation must be placed in locations where animals naturally approach and cross the highway. Results of a study funded by the Colorado Department of Transportation indicate that mid- and large-sized mammals focus crossing activity at specific locations that are correlated to features of the surrounding habitat and the roadway itself. Therefore, both the design of a highway and its placement in the landscape should be considered when creating mitigation projects to help wildlife safely cross a highway. It is important to note that no single set of variables identifies all preferred crossing locations. Because every landscape and every highway is unique, identifying the best location for each mitigation project must be approached individually. However, the study results suggest a set of guidelines, comprising the following: (1) use habitat suitability as the primary indicator of crossing activity; (2) consider how landscape structure interacts with habitat suitability to either increase or decrease the level of use an area of suitable habitat receives by a particular species; (3) consider how the design of the existing highway interacts with habitat suitability and landscape structure to influence crossing behavior; (4) synthesize this information by mapping the landscape and roadway features/conditions likely to be associated with crossing or that are attractive/repellant to the species present. Use these maps to identify the most likely crossing locations. Finally, because the preferred habitat and behavior of a given species can vary across its range, it is important to employ professionals familiar with the landscapes and species of concern on the analysis team.