Evaluation of Measures to Promote Desert Bighorn Sheep Highway Permeability: U.S. Route 93

This study evaluated desert bighorn sheep–highway relationships from 2008 to 2010 along a 17‐mi stretch of U.S. Route 93 (U.S. 93), in northwestern Arizona. Highway reconstruction between mileposts (MP) 2.3 and MP 17.0 was completed in October 2010. The research objectives were to: 1. Assess sheep movements, highway crossing patterns, distribution, and determine permeability. 2. Investigate spatial and temporal patterns of sheep highway crossings and relationships to traffic volume. 3. Investigate spatial and temporal sheep‐vehicle collision patterns. 4. Assess the impact of highway reconstruction activities on sheep movements, habitat use, and permeability. 5. Establish baseline data for pre‐ and during‐reconstruction movements, highway crossing and passage rates, and sheep-vehicle collisions against which to conduct a sound post‐reconstruction assessment. Researchers instrumented 38 desert bighorn sheep (Ovis canadensis) with GPS collars. Sheep crossed the highway 340 times. U.S. 93 constituted a significant barrier to sheep passage, as passage rates averaged just 0.07 crossings/approach. Passage rates varied by season, with summer rates higher than winter and spring rates given that sheep exhibited increased tolerance to traffic during summer when crossing U.S. 93 in pursuit of water. The highway reconstruction project’s significant measures promoting sheep highway permeability—including three new wildlife overpasses, other bridges to accommodate wildlife passage, and ungulate funnel fencing—are expected to have a beneficial impact on bighorn sheep crossing patterns. Further monitoring will assess the efficacy of these measures on increasing sheep crossings and reducing collisions along U.S. 93.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Figures; References; Tables;
  • Pagination: 86p

Subject/Index Terms

Filing Info

  • Accession Number: 01506781
  • Record Type: Publication
  • Report/Paper Numbers: FHWA‐AZ‐14‐677
  • Contract Numbers: SPR‐000‐1(175) 677
  • Files: TRIS, ATRI, USDOT, STATEDOT
  • Created Date: Feb 10 2014 4:47PM