Four types of Wildlife Crossings you might see in Minnesota

Wildlife crossings are making their way into the mainstream, popping up on roads throughout the country. These crossings are structures where animals can cross roads safely, avoiding the commotion and danger of vehicle traffic while simultaneously connecting habitats on either side of the road.

Minnesota has several already, but do you know the types? The following will help to distinguish between the four different kinds of crossings you may see on our Minnesota roads.

Culvert

If you have never seen a culvert crossing, the first reason would be that they cross beneath the road. Often, culverts are installed for water passage, but can also be used for pedestrian or wildlife crossings. Culverts can be made from reinforced concrete or pipes. One wildlife crossing in Minnesota is a box culvert design: a pre-cast, four sided structure that is made of concrete. Since they are installed beneath roads, box culverts are more resistant to environmental factors- of which we have many in Minnesota. They are designed to last between 75 and 100 years with very little maintenance.

Box culvert in North Carolina.Photo by City of Greenville | Public Domain

A box culvert like the one above was installed in 2021 just outside of Claremont, Minnesota under Highway 14. It is large enough for a deer to cross through, but also allows smaller animals to benefit.

This particular crossing was installed during construction of Highway 14, with the goal of minimizing deer-vehicle collisions. Highway 14 slices through the winter and summer habitats of Minnesota deer, meaning their corridor was bisected. This box culvert helps them travel freely between the two locations and reduces their need to cross the road.

Turtle Tunnel

Snapping turtle crossing the road.Photo by Courtney Celley/USFWS | Public Domain

A turtle crosses the road to get to its nesting grounds, but they aren’t known for moving very swiftly. Turtle populations in Minnesota are heavily impacted by vehicle collisions and are so small that a car can often keep driving without any damage at all. Unfortunately, what is a small bump to us is a life-threatening incident to them. Vehicle collisions with turtles often end up killing the turtle, further negatively impacting their populations. 

A turtle tunnel, which also accommodates reptiles, amphibians and even some birds, allows safe passage beneath a roadway similar to a culvert. The difference here, however, is the size. 

Passage for turtles and other small wildlife.Photo by Kevin Hining/NCDOT | Public Domain

In 2014, the first turtle tunnel was installed in Washington County, Minnesota near Big Marine Lake. This particular tunnel, designed by ACO Wildlife, has three components: the tunnel, the tunnel entrance, and the surrounding barrier that guides critters inside. The tunnel also has holes on the top side of the structure, allowing light through. 

A passage solely for turtles may sound adorable, if even a little silly. But two species of turtles native to Minnesota are threatened and, as already mentioned, cars are often to blame. Turtles are crucial to our ecosystem and benefit greatly if they can be protected in their efforts to cross traffic. Since 2014, at least three more tunnels have been installed throughout the Twin Cities.

Passage Bench

A passage bench is the most common wildlife crossing in Minnesota, and if you have spent any time near our many rivers and lakes, you have certainly seen one and maybe even used one. 

Passage bench under bridge.Photo by USDA/US Forest Service | Public Domain

A passage bench is a gravel or dirt surface added next to bridge riprap (the rocks near the bridge). Put simply, it is a walkable surface and allows for foot traffic beneath a bridge that crosses over water.

Minnesota has spent the past 20 years assuring that passage benches are added to our many waterway bridges. The first one was added experimentally in 2005. After success with the project and perfection of the technique, they became the standard set procedure under bridges for any new construction after 2011. Without the passage bench, animals would either be forced into the water, or up across the road. With them, animals can easily pass beneath bridges thus further preventing collisions and animal loss.  

Bridges

The final category of crossing is the simple bridge, similar to a pedestrian bridge. These, however, are designed solely for animals to cross. Many bridge or overpass crossings are bedded with plants, grass, or gravel to make the crossing similar to the surrounding land. This surface can make it easier for animals to adapt to and use. 

Bridge crossings often accommodate larger mammals such as deer, elk, moose, wolves and bears. 

Wildlife CrossingPhoto by Hagai Agmon-Snir | CC-BY-SA-4.0

These beautiful overpasses are one type of wildlife crossing that we don’t yet have in Minnesota. However, states surrounding us, including Wisconsin and South Dakota, are considering them, and states out West such as Arizona and Utah already have operational bridge crossings that have proven successful.