HIGHWAY MORTALITY IN DESERT TORTOISES AND SMALL VERTEBRATES: SUCCESS OF BARRIER FENCES AND CULVERTS

Highway traffic is an important cause of mortality for many species of animals, including the desert tortoise (Gopherus agassizii), a species state- and federally-listed as threatened. Besides direct mortality and facilitating illegal collections, roads and highways impact tortoise populations through restriction of movement. The restriction of movement may result in fragmenting populations, thereby increasing the probability of local extinctions and the potential for inbreeding and inbreeding depression. Fragmentation of populations and restriction of gene flow may increase with increases in traffic volume, width of highways, and time. Because there are many roads and highways throughout the habitat of the desert tortoise, the potential for road kills to affect tortoise populations is high. Consequently, reducing road kills could help to facilitate recovery of tortoise populations. Barrier fences are a potential mitigation, but they also increase population fragmentation. Culverts beneath the roadway may reduce fragmentation by facilitating movements of tortoises between both sides of the road. This paper discusses a scientific research project designed to learn the effectiveness of a highway barrier fence built to aid in the recovery of desert tortoise populations along California State Highway 58 in the western Mojave Desert of California. The paper characterizes the extent of road kills for several species of small terrestrial vertebrates, the demographic impact highway mortality has had on surrounding tortoise populations, the effectiveness of the barrier fence at reducing mortality along the highway, and the use of culverts by tortoises and other small vertebrates.

• Supplemental Notes:
  • Also published by Florida DOT as a paper in FL-ER-58-96, "Trends in Addressing Transportation Related Wildlife Mortality: Proceedings of the Transportation Related Wildlife Mortality Seminar (June 1996).
• Corporate Authors:

  Florida Department of Transportation

  Haydon Burns Building, 605 Suwanee Street
  Tallahassee, FL  United States  32301

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Boarman, W I
  • Sazaki, M
• Conference:
  • Transportation and Wildlife: Reducing Wildlife Mortality and Improving Wildlife Passageways Across Transportation Corridors
  • Location: Orlando, Florida
  • Date: 1996-4-30 to 1996-5-2
• Publication Date: 1996-8

Language

• English

Media Info

• Features: References;
• Pagination: p. 169-173

Subject/Index Terms

• TRT Terms: Culverts; Deserts; Fatalities; Fences; Habitat (Ecology); Measures of effectiveness; Traffic mitigation
• Uncontrolled Terms: Effectiveness; Fragmentation; Mitigation; Mortality; Turtles
• Geographic Terms: California
• Old TRIS Terms: Small vertebrates
• Subject Areas: Bridges and other structures; Design; Environment; Highways; Planning and Forecasting; I21: Planning of Transport Infrastructure;

Filing Info

• Accession Number: 00745664
• Record Type: Publication
• Report/Paper Numbers: FHWA-PD-96-041
• Files: TRIS, USDOT, STATEDOT
• Created Date: Feb 2 1998 12:00AM