Evaluating the efficacy of road crossings
As long linear features on the landscape, roads and highways impact wildlife and wildlife habitats that are disproportionate to the land they occupy. Roadways affect wildlife through direct loss and fragmentation of habitats, as a source of additive mortality for wildlife and by disrupting animal movements. A variety of strategies have been used to mitigate the impacts of transportation systems on wildlife. Most attempts to evaluate wildlife passageways focused on documenting wildlife use of structures. While tracking beds, cameras, and counters document what animals are using structures, they provide little information on those species or individuals that fail to use a structure. In contrast, radio-tracking, trapping and tracking studies are more useful for determining the extent roadways inhibit wildlife movements and the degree to which passage structures mitigate these effects. To fully assess the effectiveness of wildlife passageways, a combination of monitoring techniques are needed to evaluate structure use and the extent to which transportation systems affect animal movements. In evaluating the effectiveness of wildlife passage structures it is also important to have an idea of how much wildlife passage is enough to determine that a particular project is a success.