Evaluation of Bighorn Sheep Overpass Effectiveness: U.S. 93 Long Term Monitoring

Bighorn-vehicle collisions are a safety concern to motorists. Furthermore, highways block animal movements between seasonal ranges or other vital habitats, fragment habitats and populations, reduce genetic interchange, and disrupt viable population processes. Recent research on desert bighorn sheep movements and crossing patterns associated with US 93 point to the barrier created by this highway through the largest bighorn sheep population in Arizona (AZ), as well as the impact of bighorn-vehicle collisions (McKinney and Smith 2007). US 93 (MP 2-17) was reconstructed from a 2-lane to a 4-lane divided highway beginning in early 2009 and was completed in late 2010. Concerns exist that this reconstruction could further fragment bighorn habitat and contribute to increased bighorn-vehicle collisions.The Arizona Department of Transportation ( ADOT) constructed 3 wildlife overpasses (the first in AZ) and 2 bridges, with fencing linking the structures to promote bighorn passage across the US 93 corridor while reducing motorist collisions with sheep. This represents a tremendous commitment on the part of ADOT and warrants thorough evaluation to assess the efficacy of overpasses in promoting permeability, particularly since few overpasses exist in North America. To assess the efficacy of the planned US 93 wildlife overpasses in promoting permeability, it is necessary to compute bighorn passage rates as an objective metric, comparing passage rates before and after the passage structures are completed using GPS telemetry (Dodd et al. 2007). Wildlife use of the overpasses will be monitored by video surveillance. Research here will complement ongoing studies along SR 260, I-17, I-40, US 89, and SR 64 and together they provide valuable insights into the impact of traffic volume on a range of wildlife species and approaches to mitigate highway and traffic impact.


    • English


    • Status: Completed
    • Funding: $245000.00
    • Contract Numbers:


    • Sponsor Organizations:

      Federal Highway Administration

      1200 New Jersey Avenue, SE
      Washington, DC  United States  20590

      Arizona Department of Transportation

      Motor Vehicle Division, 206 S. 17th Avenue
      Phoenix, AZ  United States  85007
    • Project Managers:

      Kombe, Estomih

    • Performing Organizations:

      Arizona Game and Fish Department

      2221 West Greenway Road
      Phoenix, AZ  United States  85023-4399
    • Principal Investigators:

      Gagnon, Jeffrey

      Schweinsburg, Ray

    • Start Date: 20110705
    • Expected Completion Date: 0
    • Actual Completion Date: 20170630
    • Source Data: RiP Project 29010

    Subject/Index Terms

    Filing Info

    • Accession Number: 01498581
    • Record Type: Research project
    • Source Agency: Arizona Department of Transportation
    • Contract Numbers: SPR-710
    • Files: RiP, STATEDOT
    • Created Date: Nov 19 2013 1:00AM