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Institute of the Environment

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Studies from different continents have proved amphibians to be the most frequently killed vertebrates on roads. In Central-Europe their ratio is between 70 and 88 percent. Local populations are known to become extinct or genetically isolated, and avoidance is also recognised, especially where the road network is dense and the traffi c is intensive. Besides ecological and conservation considerations, amphibian road kills also present a hazard for motorists when amphibians migrate in large numbers. Mitigation measures for amphibians have been applied since the 1960s. In Central-Europe the fi rst amphibianrelated culvert modifi cation occurred at Parassapuszta, Hungary, in 1986. A number of amphibian-oriented mitigation measures have been made in the region under roads and motorways since then, especially after 1995. The aim of this paper is to describe the main features of these constructions, overview the different designs, and make suggestions for their improvement as well as for future amphibian-oriented mitigation measures in general. A total of 31 road sections was monitored. Besides amphibian tunnels, game passages and game bridges were also investigated. Both the detailed characterisation of the technical solutions and the survey of amphibian populations and habitats were included in the methodology. The investigation of the tunnel systems showed a great diversity, e.g., in tunnel and fence material, their position in relation to the road, and connections between them. For economical reasons concrete tunnels were the most common. Both circular and square cross-section tunnels were in place. The accessibility of the entrance was a possible problem, especially in areas where erosion is considerable. Plastic mesh and concrete fences were both applied with a height fl uctuating between 45 and 70cm. Plastic fences are usually fi xed to wooden poles, which need to be checked before the migration period starts. However, the advantage of such fencing is fl exibility, which makes possible, e.g., the turning back of its ends to prevent amphibians from getting on the road. Some systems did not work because certain elements (usually fences) were in bad condition. Elsewhere lack of maintenance reduced the effi ciency of mitigation measures. Missing elements should be replaced immediately, even if the amphibian migration period is over, because other animals, e.g., small mammals, also use these systems. The lowest distance between tunnels in amphibian mitigation systems is 40m in the region (Kudowa Zdrój, Poland). Usually, amphibian tunnels were placed 50-100m from each other, which is an acceptable distance. In case of adequate fencing, game passages and game bridges would also be appropriate for the crossing of amphibians as well as reptiles and small mammals, similar to slightly modifi ed existing culverts under high road mortality sections, and there would be a need for such conservation improvements at several sites. As a result of this work, several recommendations on the maintenance of amphibian tunnels and fences were also developed. Further cooperation among different agencies and organisations was urged, nationally as well as internationally. The improvement of public relation activities on fauna passages also seems to be needed for the effective protection of wildlife on roads.

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