On The Move: Barriers To Wildlife Migration

Each year, millions of animals embark on seasonal migrations that move them from one region to another. This phenomenon is found in all groups of animals including mammals, birds, fish, reptiles, insects, and amphibians.

Here in Oregon, we host an array of moving wildlife populations throughout the year. One of the most ubiquitous migrators of the Pacific Northwest are our salmon and lamprey populations.

The fish are diadromous (there’s a vocab word for you!), meaning they move between freshwater and saltwater. In adolescence, these fish migrate from their riverside birthplace out to the open ocean, where they mature until they are ready to return to spawn and create the next generation. The routes between species’ summer and winter habitats are known as migration corridors.

These paths, travelled by generations of animals, are increasingly difficult to pass due to human infrastructure. Busy roadways, restricted access through walls and barriers, and even light pollution are making it more difficult and dangerous for animals.

In the 1980s, over 10 million Western monarchs arrived at their winter home in coastal California. In 2017, there were only 300,000. For mule deer in the Cascades, winter habitats are becoming more difficult to travel to, and increased traffic on Highway 97 presents an increasingly dangerous obstacle.

“Every animal has to move to fulfill its full suite of life needs, and when a road is smack in the middle of that particular need to cross, a problem is created,” says Simon Wray, a Conservation Biologist from Oregon Department of Fish and Wildlife. “Animals will follow vegetation cover, so they can get up to a highway while they’re hidden and hop across. [Or] it could be topography. Animals will follow ridgelines, stuff like that.”

In Oregon, over 7,000 collisions are reported annually. The death toll of animals is estimated to be 3-5 times higher than that, with up to 35,000 animals killed on roads in this state alone. Accidents account for up to 20% of mule deer deaths. Each year, an average of two people die from animal-related wrecks statewide. Wildlife collisions cause an estimated $44 million in vehicle damages yearly.

With statistics like these, it’s in everyone's best interest to protect and strengthen habitat connectivity for migrating wildlife. At the Oregon Wildlife Foundation we are partnering with the Oregon Department of Fish and Wildlife, Oregon Department of Transportation, Oregon Hunter’s Association, Oregon Watershed Enhancement Board, Mule Deer Foundation, and Protect Animal Migration to fund the Gilchrist Wildlife Undercrossing Project.

This undercross is being built in Gilchrist, Oregon as an added feature of a passing lane project by the Oregon Department of Transportation. As a busy Central Oregon intersection, Gilchrist has been identified as a hotspot for wildlife collisions; the project hopes to reduce the number of deer and elk being stuck by vehicles by providing an alternative to crossing busy Highway 97.

In areas where similar underpasses have already been implemented, the numbers are remarkable. The Lava Butte Wildlife Crossing was completed in 2012, and has reduced wildlife-vehicle collisions in the area by 85%. Beyond benefitting deer and elk, game cameras have captured over 41 different species us