Talk Roads and railroads as barriers for bats in Sweden

Bats are affected in different ways by roads and railways. In a forest dominated landscape roads and railways create openings in the landscape, and for species of bats linked to forest habitats these might act as barriers. Roads and railways also influence bats through noise and light. In some cases wildlife crossing (both above and under the road) are used to compensate for the barrier effect, but the function and the design of these are still under evaluation and development. This project is the first time the impact of roads on bats are tested in a north European hemi-boreal landscape. Landscape and species composition, abundance of bats and the light condition differ from previous studies. Bats (all species occurring in the area) were surveyed along a high-way (road number E18 between Västerås and Stockholm, Sweden). In addition, a study was made about the flight behaviour of Brandt's bat (Myotis brandtii) and whiskered bat (Myotis mystacinus) by using radio-tracking, in the vicinity of the highway and the railway. The results from the radio-tracking showed that Brandt's bats and whiskered bats were foraging on both sides of the road, and they frequently used the wildlife crossing, both under and above the road, but in general they did not pass the road. Thus, the road worked as a barrier and wildlife crossings are used for foraging and commuting. However, there are exceptions when bats pass the road, and also forage along the tree-line in the mid part of the highway, as shown in the highway survey. By analysing these cases, it is possible to learn more about where and how wildlife passages should be constructed, and to identify problems early in the planning process.

bats, infrastructure, wildlife crossing, landscape ecology, conservation