Road Ecology Center

The effects of roads and railways on animals such as direct mortality caused by these infrastructure elements were recognised as early as the end of the ninetenth century. In the first half of the twentieth century further evidence gathered related to different vertebrate groups. Besides the increasing amount of information available on the environmental impact of roads and railways in the second half of the twentieth century, crossing structures, game bridges, amphibian tunnels and game passages were built as mitigation measures to provide corridors over or under roads and railways, especially in Europe. In most cases, however, they were aimed to help one animal group or species. With the development of an ecosystem-level approach, however, the investigation of the possible involvement of these constructions in helping non-target groups also started together with building green bridges. A further recognition of the special needs of certain species also led to the development of new structural elements, for example tunnels built within green bridges to help burrowing animals to cross.

Mitigation measures representing all animal crossing structures in Hungary were selected to study their use by amphibians, reptiles and small to medium-sized mammals. They included a toad tunnel system with eight tunnels and approximately five-hundred meter concrete fences along road 8518. and six tunnels under the bicycle road running along the same road stretch at Lake Fert?, one wet and two dry passages of one meter in diameter under the M1 motorway with 60 centimetre high concrete fences and two twelve meter wide game bridges with game fences over the same motorway. All sites are located in the same, Arrabonicum fauna district in the western part of Hungary. Due to differences in the studied animal groups a complex sampling methodology was applied. Besides site visits during the day to find the shed skins of reptiles, footprints of mammals on sand beds or their droppings in the passages, the mitigation measure use of amphibians was also investigated in night visits especially during the breeding season while mammals were also caught by baited traps and hair traps were also used. To check the efficiency of the toad tunnel system the frequency of amphibian road kills were also studied.

Amphibians were found both in the tunnel system and the wet passage under the road, but their presence was not proved either in the dry passages or on the game bridges. The tunnel system worked very efficiently, i.e. it lowered road kills by at least 90%, which can even be improved by maintenance. As a consequence, more amphibians died on the bicycle road and a side road nearby than on the main road. The mitigation measure use of reptiles was proved at all investigated sites even if none of the constructions were planned to provide corridors for that animal group. Grass snakes were found in toad tunnels and passages, sand lizards on game bridges. An important difference between them was that snakes moved through the tunnels while lizards lived on them and used game bridges as a habitat. Small mammals used all investigated measures, vole and mice species were trapped in all of them. What is more, they used tunnels as part of their habitats. Besides, shrews were present in toad tunnels as well the presence of foxes and martens was also indicated. However, their road kill was low in the section studied.

During the study period eight species of amphibians as well as mammals and two reptiles were proved to utilise the investigated crossing structures. Besides providing corridors, large constructions, such as game bridges also function as habitats e.g. for lizards. The use of large, mammal-oriented mitigation measures by amphibians and reptiles is needed to study further as well as efforts should be made to construct more passages or alter existing structures in the future to lower habitat fragmentation along transportation infrastructure.