Biodiversity and Conservation

, Volume 17, Issue 7, pp 1685–1699

Response of carnivores to existing highway culverts and underpasses: implications for road planning and mitigation

  • Clara Grilo
  • John A. Bissonette
  • Margarida Santos-Reis
Original Paper

DOI: 10.1007/s10531-008-9374-8

Cite this article as:
Grilo, C., Bissonette, J.A. & Santos-Reis, M. Biodivers Conserv (2008) 17: 1685. doi:10.1007/s10531-008-9374-8

Abstract

Roads with high traffic volumes are a source of animal mortality, can disrupt normal animal movements and dispersal, and may represent a potentially serious threat to wildlife population stability and viability. Retrofitting existing structures built for other purposes (e.g., drainage culverts or small below-grade access roads) to facilitate wildlife crossing by animals and to reduce mortality may be expensive if modifications to the existing structures themselves were involved. However, the environmental context surrounding these structures may influence the willingness of animals to cross, and management of some of these attributes may enhance the attractiveness of these structures. Culverts and underpasses are two common structures along roads in Portugal. We quantified the response of small and medium-sized carnivores to the presence of both types of existing passages by determining: (1) frequency of use; (2) whether use differed by type of passage, and if so; (3) by examining if associated environmental attributes might explain the differences observed. We surveyed 57 different passages along 252 km of highway with a total sampling effort of 2,330 passage trap-days. The mean passage rate for carnivores combined was 0.7 complete passages per crossing structure per day. Crossings by weasel, polecat, otter, and wildcat were infrequent or absent. Red fox, badger, genet and Egyptian mongoose used the crossing structures regularly and without obvious preference; stone marten preferred underpasses. Regression analyses showed the frequency of use by carnivores varied with structural, landscape, road-related features, and human disturbance with 17 of 26 (65%) attributes being significant. Larger passages with vegetation close to the passage entrances, favorable habitat in the surrounding area, and low disturbance by humans were important key features to regular use by the guild of species studied. Mitigation planning in areas with ecological significance for carnivores will be beneficial. Structural attributes and human disturbances are more difficult or expensive to change, even though related significantly to crossing use. Management of vegetation at passage entrances and restricting human use near passages in carnivore suitable areas may substantially improve crossing attractiveness for the guild of carnivore species.

Keywords

Carnivores Conservation Habitat connectivity Non-wildlife passages Road design 

Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  • Clara Grilo
    • 1
  • John A. Bissonette
    • 2
  • Margarida Santos-Reis
    • 1
  1. 1.Departamento de Biologia Animal/Centro de Biologia AmbientalFaculdade de Ciências, Universidade de LisboaLisboaPortugal
  2. 2.USGS Utah Cooperative Fish and Wildlife Research Unit, Department of Wildland Resources, College of Natural ResourcesUtah State UniversityLoganUSA