Bats are an important component of Florida's environment and several species use highway bridges as roosting sites. As the primary agency managing highway bridges, the Florida Department of Transportation (FDOT) needs additional information on bat roosts in bridges in order to conserve roosting bats while safely and effectively maintaining bridge functions. To study bat roosts in bridges, the authors looked for evidence of bats at randomly and non-randomly selected bridges in Florida. Combining both random and non-random samples, they found 151 bridges occupied by roosting bats. Bat bridges occurred throughout the state, except in far south Florida and the Keys, and 55% of occupied bridges occurred in north Florida. They found 4 species of bats roosting in bridges, but could not identify the species of bats present at 38 (25.2%) of the bridges. Most occupied bridges supported only 1 species of bat, but 35 bridges contained multiple species. Using FDOT bridge data, they compared all occupied bridges with the randomly sampled unoccupied bridges and found a significant association between bridge structure type and presence of bats. More bats than expected by chance roosted in prestressed concrete bridges with multiple beams. They found bats roosting only in concrete bridges or on the concrete components of steel bridges and never on metal surfaces or in timber bridges. Bridges with bats were constructed before 1993 and were significantly older than bridges without bats. The mean year of construction for occupied bridges was 1969, while the mean for unoccupied bridges was 1977. Average daily vehicle traffic was significantly greater across the unoccupied bridges than across bridges with bats. Unoccupied bridges averaged 32,953 vehicles daily while bridges with bats averaged 16,152 vehicles. Neither total length nor bridge height differed significantly between bridges with bats and those without. Suggestions for providing roosts in new, repaired, or reconstructed bridges are provided, as are guidelines for minimizing conflicts between bats and bridge inspection and maintenance crews.

  • Corporate Authors:

    Florida Fish and Wildlife Conservation Commission

    3911 Highway 2321
    Panama City, FL  United States  32409

    Florida Department of Transportation

    605 Suwannee Street
    Tallahassee, FL  United States  32399-0450
  • Authors:
    • Gore, J A
    • Studenroth Jr, K R
  • Publication Date: 2005-3


  • English

Media Info

  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 64 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00989320
  • Record Type: Publication
  • Report/Paper Numbers: Report No. BD433,, F2147-02-05-F,, Final Report
  • Contract Numbers: BD433
  • Created Date: Apr 28 2005 12:00AM