Determining the Potential Mitigation Effects of Wildlife Passageways on Black Bears

North Carolina’s U.S. Highway 64 is currently being expanded from a two-lane road to a four-lane divided highway from Raleigh to the Outer Banks. Concerns exist that collisions with vehicles may affect the demographics of wildlife populations and that potential disturbances and fragmentation associated with the highway may affect the ecological integrity of the landscape, particularly with regard to large carnivores. In response to these concerns, the North Carolina Department of Transportation (NCDOT) included three wildlife underpasses into the design of a 19.3- km section of the new U.S. Highway 64 in Washington County. The locations of the wildlife underpasses were determined based on a study by the North Carolina Wildlife Resources Commission during 1999. Areas that received frequent wildlife use were identified based on surveys of track counts, ditch crossings, and infrared cameras. The resulting data were used in combination with a geographic information system (GIS) to identify travel corridors for wildlife. Once the locations of the wildlife underpasses were established, the University of Tennessee initiated research in 2000 to determine whether wildlife passageways can mitigate impacts from highways. The authors chose a wide- ranging carnivore, the American black bear ( Ursus americanus ), as the focus species of the study because of its dependence on regional landscapes. The authors developed an experimental study design that will allow for collection of data before and after highway construction on a treatment and a control area. During the pre-construction phase of the study, the authors have collected over 6,000 locations on a total of 35 bears to document home-range sizes, activity patterns, movements, and habitat use. The authors are also analyzing 337 DNA samples from hair collected at 140 barbed-wire hair traps to estimate population density and to determine genetic relatedness within and among the two populations. Finally, the authors are using 243 photographs of wildlife from infrared cameras to measure use of the areas where the highway underpasses will be constructed. Field data collection during the pre-construction period was completed in June 2001; post-construction data will be gathered and compared after the anticipated completion of the highway in 2004.