Notes from the Field: Wildlife Crossings
Highways present formidable barriers to wildlife movement. Thousands of deer and elk are hit by vehicles and injured or killed every year in Oregon; these wildlife-vehicle collisions also result of course in human injury, loss of life, and many thousands of dollars in property damage. The state’s human population, traffic counts, and instances of accidents due to distracted drivers are all increasing, while mule deer populations are declining. Highway underpasses and overpasses have demonstrated benefits in dramatically lowering the number of wildlife-vehicle collisions regionally, nationally, and even globally. Oregon has been lagging behind other western states in the construction of wildlife passage projects, but in recent years there is some good news.
As development and land conversion has continued apace in Oregon over the decades, the relentlessly expanding human presence is shifting the landscape from one in which our settlements were connected by thin corridors of built infrastructure linking them across vast expanses of natural lands, to increasingly one in which shrinking patches of intact natural habitat are connected by thin corridors providing wildlife passage across expanses of degraded, fragmented, and otherwise impacted lands. These corridors have become critically important for wildlife, especially wider-ranging species that move across the landscape on a large scale in order to complete seasonal migration, follow the availability of forage or prey, and disperse from natal to breeding territories. Indeed, biologists have come to understand that constant and extensive movement across the landscape is a defining characteristic of the fundamental behavior for many wildlife species and that wildlife corridors are essential to accommodating that mobility; there is even an emerging field of research referred to as “movement ecology.”
U.S. Highway 97 runs north-south right smack across a broad east-west wildlife corridor especially important for mule deer migrating between higher elevation summer range and lower elevation winter range. The highway is a fearsome barrier to wildlife, and tracking data clearly showed its course through Central Oregon as one of the worst spots in the state for wildlife-vehicle collisions. A partnership between ODOT, ODFW, the US Forest Service, hunting groups, and conservation organizations has resulted in new wildlife underpasses beneath the highway, constructed in conjunction with widening projects. Two underpasses between Bend and Sunriver, one that accommodates cross traffic and wildlife and the other for wildlife alone, have already reduced collisions with mule deer by 86%. Their effectiveness is believed to be enhanced by miles of 8-foot fencing paralleling the highway on either side and funneling animals to the underpasses. A third underpass beneath Highway 97 is now finishing construction just north of Gilchrist. Wildlife cameras have already documented dozens of species making use of these passages to safely get across the highway. Mule deer exhibit remarkable fidelity to specific pathways, so it is hoped that over a number of years of social learning these underpasses will become even more important.
A five-minute ODOT/ODFW video describing the newest Highway 97 underpass project can be viewed here.
Central Oregon LandWatch is firmly committed to continue working on protecting wildlife corridors.