What type of amphibian tunnel could reduce road kills?

Abstract

Increased traffic volumes worldwide are contributing to amphibian declines, and measures to reduce the occurrence of road kills are needed. One possible measure is the construction of underpasses through which animals can pass under roads, but little is known about whether amphibians will choose tunnels if given a choice or about their preferences for different tunnel types. We tested the preferences of three anuran species for two kinds of concrete amphibian tunnels currently used in France. One was a tunnel lined with soil, the other a bare concrete pipe. The animals could use the tunnels or bypass them over a grassy area. Water frogs Rana esculenta and common toads Bufo bufo showed a preference for the tunnels, whereas agile frogs Rana dalmatina avoided them. Among the individuals that chose either of the tunnels, all species showed a significant preference for the tunnel lined with soil. These results indicate that species differ in their preferences and in their likelihood of using underpasses when given a choice. This highlights the fact that there is no unique solution to the problem, and underpasses are only one of the possible mitigation measures that need to be assessed. © 2004 FFI.