In an effort to cut down on the mortality rate of animals who are hit by cars, Banff National Park has constructed a number of wildlife overpasses and underpasses. In the photo below, note the trees growing on the overpass. Bears, elk, deer, wolves, cougars and more use these passages to safely cross the TransCanada Highway, which bisects the park.
At both the under and overpasses, wires have been strung across the entryways. When bears and other animals climb over or under these wires, pieces of their hair get snagged. Biologists have been using this method of DNA sampling to figure out exactly which animals are using the passes. The study is ongoing, but so far mortality rates have been reduced considerably, including 80% less bear mortalities.