Background:
With the rapid expansion of road networksin proximity to desert bighorn sheephabitat, and the increased use of high animal fencing along suchroads to reduce wildlife/vehicle collisions, the need for proper design and placement ofwildlife crossing structures becomes imperative to allow for animal movement and reduce the potential for habitat fragmentation. During the realignment and improvement of State Highway 68 between Kingman and Bullhead City, Arizona, 3 different underpasses were incorporated to facilitate movement of desert bighorn sheep. Our objective was to determine the efficacy of each of these underpasses and evaluate design, structure, and placement features that may affect desert bighorn sheep use. This information can be used to help design future wildlife underpasses to increase permeability of highways constructed near desert bighorn sheep habitat.

Location:

State Route 68 (Hwy 68) connecting Kingman to Bullhead City runs through the Black Mountains in northwest Arizona. This study was focused on the area within 10 miles north and south of Hwy 68 and from Golden Valley on the east to the Colorado River on the west. Topography ranged from mountainous terrain with steep talus slopes and rugged cliffs to dry washes among rolling hills.

Approach:
To evaluate movements of desert bighorn sheep relative to underpass placement we captured 25 adult desert bighorn sheep. We fitted animals with GPS telemetry collars with mortality sensors. Collars were set to take a GPS point every 5 to 6 hours. We captured 12 animals (6 ewes and 6 rams) north of Hwy 68 and 13 animals (8 ewes and 5 rams) to the south. We also used remote cameras to monitor use of the underpasses.

Benefits: 
By monitoring wildlife use of man-made crossing structures that are already built along the highway, we have gained an understanding of what kinds of crossing structure designs work for many wildlife species. Our findings will benefit conservation and management of desert bighorn sheep populations by effective placement of species friendly crossing structures. This will ensure highway permeability and enable fragmented animal populations to access isolated resources and breed with other populations across the highway. The information we gather from this study helps guide recommendations for placement of effective future wildlife crossing structures, which will make the highway safer for desert bighorn sheep and motorists.

For more information contact: 
Michelle Crabb, Arizona Game and Fish Department
5000 W. Carefree Highway, Phoenix, AZ 85023
E-mail: mcrabb@azgfd.gov

Kirby Bristow, Arizona Game and Fish Department
5000 W. Carefree Highway, Phoenix, AZ 85023
E-mail: kbristow@azgfd.gov