Motorists on Highway 93 North have been driving over wildlife like crazy in the past year, without ever noticing.
Bears, bobcats, river otters and owls have discovered a network of 42 underpasses built into the roadway between Evaro and Polson. Photographic evidence shows a host of critters using the tunnels as cars zoom overhead.
"This whole concept of road ecology is catching on," Confederated Salish and Kootenai Tribes wildlife biologist Whisper Camel said of the network. "This one may be the biggest in the country."
The underpasses range in size from 4-foot-diameter culverts to 22-foot-wide tunnels. There's also one overpass under construction north of Evaro. And eventually, there will be a few turtle-sized pipes along the Ninepipe National Wildlife Refuge.
Many have an infrared digital camera installed with a motion-detector shutter trigger. Camel checks them monthly, cataloging everything from great horned owls to human hunters using the routes. In the year they've been in place, she's collected between 40 and 150 "animal occurrences" a month.
"I was really surprised by the river otters," Camel said. "It's not unlikely they would use it, but there are so few of them, you don't really see them that often - certainly not crossing the road."
She was also happy to snap a cow elk using a tunnel. That's technically a big deal, because elk tend to be the most skittish species around new features. They're also a major hazard for motorists.
And that's the overarching reason for adding the underpasses to the Highway 93 North project. Montana Department of Transportation wildlife biologist Pat Basting said reducing wildlife collisions was a big part of his job.
"There've been questions from members of the public and even some transportation engineering officials, whether or not these things were really going to be effective," Basting said. "The photos reaffirm and reassure decision-makers these things do work."
In fact, a recent Western Transportation Institute study presented to Congress showed that over a 10-year period in the 1990s and 2000s, all types of traffic accidents remained relatively constant even though traffic volume has gone up. But hidden in the data was the observation that in that same period, wildlife-vehicle collisions had jumped nearly 50 percent.
Basting said traffic studies can set cash values for collisions. The calculation includes the value of the dead animal, damage to the vehicle, cost of emergency response and the average injury to driver and passengers. Using those figures, it's possible to learn how long it takes for a wildlife tunnel to pay for itself in reduced collisions.
Hitting a deer costs an average of $6,600, according to Marcel Huijser of the Western Transportation Institute. An elk collision packs a bill of $17,500.
The underpasses benefit wildlife in other ways besides keeping them out of car grilles. They restore connections between animal populations and make it safer for them to move between habitats.
Camel said the Post Creek Hill stretch of Highway 93 has claimed three grizzly bears in the past 20 years. No griz have been caught on camera yet, but one crossing was placed particularly because it spanned that corridor between the mountains and lower valley the big bears frequent.
And the cameras have caught black bears using the underpasses, as well as cougars and coyotes.
Another 31 crossing structures are on tap for Highway 93 in the Bitterroot Valley south of Missoula.