Assessment of Desert Tortoise Movement, Permeability, and Habitat Along the Proposed State Route 95 Realignment

The goal of this study was to evaluate the effectiveness of highway mitigation for reducing road mortality of Morafka’s desert tortoise (Gopherus morafkai; formerly, G. agassizii) and maintaining permeability in an effort to guide future mitigation within the range of the desert tortoise in Arizona. The research team examined existing wildlife-linkage mitigation measures along an 11-mi (17.7 km) stretch of U.S. Route 93 (US 93) and desert tortoise habitat relationships in the Black Mountains ecosystem to guide mitigation recommendations for the proposed realignment of State Route (SR) 95 between Interstate 40 (I-40) and SR 68. The work was performed in 2008 and 2009. The team identified 561 breaches along the US 93 tortoise exclusion fencing due to erosion, undercutting, and siltation. Of the 25 culverts on US 93, 9 were nonfunctional due to their inaccessibility to desert tortoises. Camera systems deployed on 8 of the functional culverts detected no tortoise use. Five tortoise mortalities were documented during weekly road mortality surveys. Researchers identified a 0.22-mi road-effect zone on either side of the highway. The research team documented tortoises, tortoise sign, or both on 52 of the 660 plots surveyed within the Black Mountains ecosystem. The proportion of area occupied (PAO) by desert tortoises varied among soil subgroups, with Aridisol soil subgroups having the highest PAO estimates. This report presents recommendations for improvements to the existing mitigation on US 93 and the proposed mitigation strategy for the planned realignment route of SR 95. These recommendations include maintenance and modification to fencing and culverts along US 93 and the placement of mitigation on the SR 95 realignment route.

• Record URL:
  http://apps.azdot.gov/ADOTLibrary/publications/project_reports/PDF/AZ650.pdf
• Corporate Authors:

  Arizona Game and Fish Department

  Research Branch
  5000 West Carefree Highway
  Phoenix, AZ  United States  85086

  Arizona Department of Transportation

  Research Center
  206 South 17th Avenue, MD075R
  Phoenix, AZ  United States  85007

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Grandmaison, David D
  • Schweinsburg, Raymond E
  • Ingraldi, Michael F
• Publication Date: 2012-12

Language

• English

Media Info

• Media Type: Digital/other
• Edition: Final Report
• Features: Appendices; Figures; References; Tables;
• Pagination: 152p

Subject/Index Terms

• TRT Terms: Culverts; Environmental monitoring; Environmental protection; Fatalities; Habitat (Ecology); Traffic mitigation; Wildlife; Wildlife crossings
• Geographic Terms: Arizona
• Subject Areas: Environment; Highways; I15: Environment;

Filing Info

• Accession Number: 01472079
• Record Type: Publication
• Report/Paper Numbers: FHWA-AZ-12-650
• Contract Numbers: SPR 000-1(173) 650
• Files: TRIS, ATRI, USDOT, STATEDOT
• Created Date: Feb 12 2013 12:15PM