Related Information:

Bozeman Pass Wildlife Channelization ITS Project - FINAL REPORT 

Bozeman Pass Wildlife Linkage and Safety Study

Bozeman Pass Paper presented at 2009 International Conference on Ecology and Transportation (ICOET)

Bozeman Pass:
Monitoring the Effect of Wildlife Fencing on Road Kill

Making Interstate 90 Safer for People and Wildlife
Animal-vehicle collisions are a growing safety, socio-economic, and ecological concern as people put growing numbers of vehicles in operation, drive more miles, and build roads that encroach ever deeper into formerly isolated wildlife habitat. More than 1 million deer-vehicle collisions alone occur each year in the United States, killing more than 200 people, injuring another 29,000, and causing $1.1 billion in vehicle damage. On the other hand, wildlife deaths caused by vehicle collisions can threaten the long-term survival of some wildlife populations and thus impact the integrity of entire ecosystems. After decades of ignoring the impacts of highways on wildlife, transportation and natural resource agencies have begun addressing such “road ecology” issues. Numerous measures to reduce animal-vehicle collisions have been tried with varying degrees of success, but the only real solution has been to keep animals off the highway surface and out of the path of vehicles. The most promising method is to use wildlife fencing in combination with wildlife passages, which keep animals off the road but allow them access to habitat on both sides. These safe crossings can reduce animal-vehicle collisions by 80-90 percent and also reduce the habitat fragmentation created by roads and other human barriers to wildlife movement.

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Craighead Institute—Monitoring Effect of Wildlife Fencing on Roadkill

In 2000, the Craighead Institute began a study to assess the amount and nature of roadkill on Interstate 90 over Bozeman Pass in partnership with the Western Transportation Institute (WTI) and the Montana Department of Transportation (MDT). Data on roadkill locations and species has been systematically collected since 2001. Over the past decade, Craighead Institute scientists surveyed the pass betweenBozeman and Livingston Montana (milepost 309.5- 333.0) 1,272 times, logging a total of 53,424 survey miles.  From January 1, 2001, through June 30, 2010, a total of 2,272 dead animals, representing 49 different species of mammals, birds and reptiles, were recorded as road kill on that stretch of interstate. The number of dead animals found along the highway, of course, represents only a fraction of the number actually killed or injured. The majority of animals killed were ungulates such as deer and elk (44%), followed by meso-carnivores such as coyotes (27%), birds (11%), medium-sized rodents (8%), small rodents (4%), unknown (3%), domestic animals (2%), large carnivores such as bears (1%), and reptiles (0.2%).

The Craighead Institute used data from the first two years of the survey to convince the Montana Department of Transportation to include a section of wildlife fencing in their plans to rebuild a bridge over the Montana Rail Link (MRL) crossing near BearCanyon. In 2004, we constructed a track bed to record the number of animals crossing underneath the existing bridge.

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Data

Two years of data were collected from this trackbed before the bridge was rebuilt. Motion-sensor cameras were also placed in culverts to record animal movements at the bridge. The bridge was replaced in 2006 and lengthened to provide more room for wildlife to cross under the highway. Wildlife exclusion fencing 8 feet high was then installed along a 1.4 mile section to direct animals underneath the interstate through the bridge passage or through a pair of large culverts. The fencing was completed in the spring of 2007, and Craighead scientists continued monitoring the road to determine the effectiveness of the fencing at reducing roadkill and increasing animal movement underneath the highway.

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RESULTS

The results have been striking: The wildlife fencing has significantly reduced roadkill in the fenced area, without increasing roadkill outside the fenced area.  In four and a quarter years of pre-fence monitoring, for instance, 49 ungulates were killed in the area to be fenced.   In three years of post-fence monitoring, only 8 ungulates have been killed there, either inside the fenced section or just outside at the fence ends.  Also, after the fencing was installed more animals travelled underneath the highway--the mean number of daily ungulate crossings under the overpass increased significantly, from 4.6 to 7.2 per day.

This Craighead Institute study has demonstrated that using wildlife fencing together with existing underpasses (or as part of already planned construction) is a very cost effective way to improve human safety, reduce roadkill, and provide safe wildlife crossings. What we have learned at this bridge site can be used in other areas of the Bozeman Pass and throughout Montana.

Outreach and Follow-up

The Craighead Institute has also been working with the Bozeman Pass Working Group (BPWG) to address ways to protect and improve wildlife connectivity and human safety in the Bozeman Pass area. This group has helped secure conservation easements and land exchanges to protect wildlife habitat on both sides of the MRL bridge crossing site. Craighead staff has given presentations to local audiences and led field trips for university students, highway professionals, and interested stakeholders.

Related projects by WTI and American Wildlands were funded my MDT to study the effects of warning signs and reduced speed on both motorist's awareness and roadkill rates. Reduced speed does seem to reduce the number of animal-vehicle collisions, but getting drivers (especially commercial trucks) to slow down is a complex issue. It is usually only effective when there is constant and highly visible law enforcement.  By far the most effective way to reduce animal hits is to keep the animals off the highway altogether.

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