Corridors for Connection By Sasha Wohlpart (with help from Dr. Jason Irwin)

Why did the snake cross the road? To get to the water in the median, of course!

Imagine if every time you needed some food or a drink of water, or to cool down on a particularly warm summer day, or just to meet up with friends, you had to cross a busy interstate. Now imagine that you could only cross that highway really, really, really slowly, or that the cars whizzing by appeared like predators and that your evolved response to this danger was to rattle your tail or to freeze in place. This is the plight of many shrub-steppe species, both big and small, whose habitat has been fragmented by roads and development.

The stretch of I-90 from Kittitas to Vantage seems benign when viewed on a map—a thin east-west ribbon connecting our communities. But a closer look reveals the imperiled shrub-steppe ecosystem that is severed by this highway and the many species whose lives are endangered and whose home territories are disconnected as a result. For example, the hills surrounding this stretch of highway is key wintering territory for the Colockum herd of Rocky Mountain elk. In winter and spring, they will sometimes graze along the shoulder and median, crossing lanes of traffic to find available forage, and eventually to make their way to the higher elevation summer range in the north. These movements endanger both elk and drivers when collisions occur. Research shows that for medium-sized species like skunks to larger ones like elk, this stretch of highway sustains an average 68.4 wildlife vehicle collisions per year. Clearly, wildlife-crossing signs alone are not sufficient.

Rarely reported are collisions with smaller, low-mobility species that barely register, if at all, for vehicle drivers. Maybe there will be a hold-the-breath moment when a driver notices something non-descript dart into the road just in front of them, and then quickly glances in the rearview mirror hoping that the small creature made it between the wheels and continued to the other side. But most often, impacts to these species, which include some that are endemic to the shrub-steppe and considered “Species of Greatest Conservation Need” by the State Wildlife Action Plan go completely unnoticed. These species include black-tailed jackrabbits, Townsend’s ground squirrels, desert striped whipsnakes, pigmy short-horned lizards, northern desert night snakes, and side-blotched lizards. These individuals may be small, but they are important members of the shrub-steppe ecosystem who, in addition to the challenge of roadways in their living spaces, are experiencing extraordinary pressure from reduced intact habitat and climate change-induced stresses like wildfires and altered water patterns.   

Wildlife-vehicle collisions are an avoidable tragedy. Corridors of connectivity for humans do not have to exist at the expense of wildlife, as modeled by the I-90 Snoqualmie Pass East Project less than 100 miles west of Vantage. There, a 15 mile stretch of I-90 is being improved for the 27,000 vehicles that drive there each day, while simultaneously integrating wildlife passages with the goal of full ecological connectivity through the vital north-south Cascade Mountains Wildlife Corridor. If you have recently driven on I-90 from Central Washington to Seattle, you have passed over the Gold Creek Wildlife Undercrossing and under the Keechelus Wildlife Overcrossing, perhaps without even knowing that there may be a bull trout below or a black bear overhead. This internationally celebrated project happened thanks to a diverse coalition of stakeholders, including the Washington State Department of Transportation (WSDOT) and Conservation Northwest, who worked together to create a solution that meets the needs of all.

The I-90 Snoqualmie Pass East Project is just over halfway done, and already it’s success has been extraordinary, as demonstrated through research and monitoring initiatives by students and faculty from Central Washington University. The positive outcomes have inspired WSDOT to plan a similar project for the Vantage corridor of I-90. The success of wildlife crossing infrastructure in this region will depend on research designed to enhance the effectiveness for shrub-steppe species, ranging from reptiles and small mammals to larger migratory species like elk. This will include baseline data collection, scheduled to begin this spring, on the distribution and dominant crossing sites of wildlife for this stretch of roadway.

Connectivity is essential for our whole community, drivers, slithers, and bounders alike. When people with diverse interests, ideas, and insights come together in partnership, solutions arise that are in the best interest of everyone involved. This is something to celebrate!

Join us on Saturday, May 11th at Get Intimate with the Shrub-Steppe and meet some of the scientists and students involved with this exciting work. ycic.org/giss

Special thanks to Jason Irwin for his dedication and work on the I-90 projects and for the information and insights used in this post.