Bears use animal bridges to breed

摘要

Animal crossings in Canada's Banff National Park allow bears to cross a major highway to breed, preventing genetic isolation. Roads can fragment animal populations, increasing the risk of inbreeding and extinction. Bridges (pictured) and underpasses could help, but it has not been clear how well they work. Michael Sawaya and his colleagues at Montana State University in Bozeman studied grizzly bears (Ursus arctos) and black bears (Ursus americanus) that used 20 animal crossings along a 45-kilometre stretch of highway bisecting the park. The researchers snared fur samples from passing bears, using barbed wire and other devices, for DNA analysis.