Study

Do dry ledges reduce the barrier effect of roads?

  • Published source details Villalva P., Reto D., Santos-Reis M., Revilla E. & Grilo C. (2013) Do dry ledges reduce the barrier effect of roads?. Ecological Engineering, 57, 143-148.

Actions

This study is summarised as evidence for the following.

Action Category

Install ledges in culverts under roads/railways

Action Link
Terrestrial Mammal Conservation

Install fences around existing culverts or underpasses under roads/railways

Action Link
Terrestrial Mammal Conservation
  1. Install ledges in culverts under roads/railways

    A replicated, controlled study in 2008–2009 of 32 culverts under roads in southern Portugal (Villalva et al. 2013) found that under-road culverts with ledges were used more by two mammal species, less by two species and to a similar extent by one species compared to culverts without ledges. Culverts with ledges were used more by stone marten Marte foina and genet Genetta genetta (data reported as model results). However, red fox Vulpes vulpes and badger Meles meles used culverts with ledges less than they used those without ledges (data reported as model results). The use of culverts by European otter Lutra lutra was not altered by the presence of ledges (data reported as model results). In January–March 2008, wooden ledges, 50 cm wide, were installed in 15 culverts and no ledges were installed in 17 culverts. Two video cameras with movement and heat sensors were placed at one entrance of each culvert. Marble dust was spread covering the width of the culvert for monitoring footprints. Each culvert was monitored for seven consecutive nights, in each season, for a year after ledge installation.

    (Summarised by: Phil Martin)

  2. Install fences around existing culverts or underpasses under roads/railways

    A replicated, before-and-after, site comparison study in 2008–2009 of 64 culverts under roads in southern Portugal (Villalva et al. 2013) found that fences connecting to existing under-road culverts did not alter mammal road mortality. After fence installation, there was a similar number of mammals killed by traffic (19 road-kills) compared to before (20 road-kills). There was also no significant difference in mammal road-kills between road sections where fences were installed (19 road-kills) and those that were not fenced (13 road-kills). In April 2008, 100-m-long fences with 2.5-cm mesh, buried to 50 cm deep and extending 50 cm above ground, were installed alongside the road at each side of 32 under-road culverts. These were in addition to existing livestock fencing. Another 32 culverts in the same area that were unfenced were selected for comparison. The number of mammals killed by traffic was recorded by highway maintenance staff for 10 months before and 10 months after fence installation.

    (Summarised by: Phil Martin)

Output references
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.


Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust