Do animals use wildlife crossings in the Netherlands An analysis of 450 crossing structures

In the Netherlands the total number of wildlife crossing structures for roads and waterways is estimated at 1725. An overview of the use of crossing types by animals is still lacking. When the use of crossing structures by animals is evaluated, it is done within the scope of the individual project. We carried out a meta-analysis of 45 field studies for assessing the target species that use crossing structures for mitigating the barrier effect of roads. The 45 field studies cover a total of more than 450 wildlife crossings, surveyed in a period of twenty years and including different types of wildlife crossings. Though in twenty years time different field methods are applied, all studies included methods for track registration. We assessed the minimum survey time for track surveys to detect 95% of the target species. We found that for practical reasons not all 45 studies meet the minimum survey time. Still the overall results for all 450 wildlife crossings are consistent enough to draw some general conclusions. Mammals and amphibians use a wide variety of wild life crossing structures. The average number of species that use Culverts with ledges is small, but only a few species avoid this type of crossing. As expected the average number of species that use Large wildlife tunnels is highest when compared with other type of underpasses. The frequency of animal usage (number of tracks) varies between crossing types and is strongly influenced by crossing dimensions, proximity to natural habitat and landscape type. We provide rule of thumbs for selecting the appropriate wildlife crossing for target species.

wildlife crossings, roads, detection probability, mitigating barrier effect