There's a stretch of Wisconsin State Highway 66 right around where it crosses the Plover River that has a reputation as a danger zone for wildlife. When animals try to cross the road, many of them don't make it. In 2015 alone, 66 turtles were killed trying to cross the busy highway.

So when the highway had to be resurfaced a few years back, the Wisconsin transportation and natural resources departments teamed up with the University of Wisconsin-Stevens Point to come up with a solution. They decided to install low fencing along the roadside and build an underpass beneath it, giving wildlife — particularly turtles — safe passage.

"Turtles took a bit to figure out what to do, but even from the outset, some turtles went right through the tunnel while others struggled to figure it out," Pete Zani, herpetologist and associate professor of biology at the University of Wisconsin-Stevens Point, tells MNN.

Maybe because it was dark, some turtles weren't sure what to make of the underpass, so Zani came up with a few improvements to make it more appealing.

"Post-installation improvements include a light-colored backdrop of sheet metal placed to reflect light into the tunnel as well as create a light-colored backdrop from the turtle-eye viewpoint," he says.

Light at the end of the tunnel

Flashing at the tunnel entrance helped turtles see that this wasn't a dark hole. Flashing at the tunnel entrance helps turtles see that this isn't simply a dark hole to nowhere. (Photo: Pete Zani/University of Wisconsin-Stevens Point)

The shiny flashing at the ends of the tunnel reflect light and show the sky, so the turtles know they have a path to cross the highway. Zani and his team literally created light at the end of the tunnel.

They also placed some grates over the tunnel to lighten the passageway, and they created one-way slippery slides, called excluders, from the roadway down to safety for small animals like toads that sometimes get trapped along the fencing and don't know how to get free.

"These were inspired by their use in other locations, like along I-70 in western Colorado where they allow deer and antelope to escape the interstate corridor," Zani says.

Not perfect, but better

Shiny flashing lightens the north entrance to the tunnel, making it less scary to wildlife. A reflector creates light while a slide (hidden in this photo) helps animals slip down from the path to safety. The pole marks the opening of the tunnel. (Photo: Pete Zani/University of Wisconsin-Stevens Point)

The changes seemed to have helped.

"The light backdrop appears to have enticed turtles to take the plunge into the tunnel," Zani says. "The passage rate is still not perfect, but better. The excluders seem to allow wildlife to escape from the roadway so fewer animals are trapped in unsuitable locations."

Since the tunnel was built in 2016, only about 40 turtles have been killed on that once-precarious stretch of road. That's a significant drop from that high of 66 in just one year.

Zani had a few other ideas that might have lowered those numbers even further for traveling turtles, but they just weren't feasible.

"We considered enlarging the tunnel or installing lights, both of which would help," he says. "but both ideas were rejected due to site logistics as well as potential expense related to upkeep."

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.

How a turtle tunnel is saving lives in Wisconsin
An underpass for turtles in Wisconsin is helping them safely cross a busy highway.