(NBC) - The mix of interstate highways and rural areas teaming with wildlife can be a bad combination.
Near the Idaho-Montana border, Interstate 90 bisects the northern Rockies. Traffic runs around the clock, with up to 10,000 vehicles passing every 24 hours, making it risky for wildlife to get across.
Researcher Chris Servheen set up heat and motion sensing cameras under two bridges to see if animals are going underneath I-90 instead. As grizzly bear recovery coordinator for the U.S. Fish and Wildlife Service, Servheen wants to ensure grizzlies can across.
This is where bears from the north could move south into currently unoccupied habitat in the Bitteroot mountains. Montana is building overpasses and underpasses to help wildlife cross roads leading up to I-90. But more than two years of study show few animals use these bridges.
"It may be that just the level of human use that occurs on these dirt roads," Servheen said. "There's ATVs and vehicles that drive through there occasionally. Just that is enough to prevent animals from using them."
Ultimately, special structures just for wildlife may be needed to get grizzlies and other animals across the interstate.