MAY TOWNSHIP, Minn. -- Minnesota's first tunnel designed specifically for migrating turtles is being installed on a rural road near Big Marine Lake in Washington County.
The special culvert system, imported from Germany, may become a prototype used by highway planners and natural resource managers throughout the state if the experiment saves lives of the roaming reptiles.
"The tunnel presents an option for that turtle to cross the road safely, but we're also hoping it solves a traffic hazard as well," Peter Mott, Washington County Parks Department planning director told KARE.
"We always see people stopping along this busy road, especially this time of year, jumping out of their cars and trying to assist these turtles across the road."
Mott said those involved in the study picked this particular spot along Washington County Highway 4 after two years of research found a high mortality rate for turtles, snakes and salamanders attempting the cross the two-lane road.
The turtle tunnel is higher than a normal drainage culvert, to keep it free of storm water. It also has slots built into the top of it, skylights if you will, to provide natural lighting.
"The light is spread all the way through the tunnel, so the turtles have a sense of something on the other side. They don't want to get themselves into a dead end situation," Mott explained.
Because turtles don't typically respond to road signs, a long fence will be erected on either side of the highway to funnel the turtle traffic toward that focal point of the tunnel. The hope among researchers is that the turtles will recognize it as the most efficient way to cross.
According to Chris Smith of the Minn. Herpetological Society turtles in that area made several migrations each year. The largest one comes in the spring when they move from their wintering homes beneath the ice near Big Marine Lake to their nesting areas in the wetlands zoned south of the highway.
The tunnel is part of a $50,000 research project funded by the Minn. Dept. of Natural Resources, the University of Minnesota and the Herpetological Society. Mott pointed out, however, that the cost of one turtle-related accident involving an auto or a motorcycle could easily exceed that amount.
The study will continue for the next two years so researchers can determine how the creatures react to the tunnel option. If other tunnels are warranted they should be less expensive than the prototype used in the Washington County project.
The female turtles especially make the journey seeking warmer, sunnier areas to make their nests, according to Smith. Later in the year the turtles will cross the road again as they return to the lake. Young hatchlings, too small to be seen by motorists moving 50 miles per hour, also make the treacherous crossing.
Smith said the area is home to common Minnesota turtles such as Painted Turtle and Snapping Turtles, as well as the more rare Blanding's Turtle, which is on the state's threatened species list. All of the turtle populations in the suburban and exurban areas have suffered higher mortality rates as traffic levels have increased in recent decades.
While turtles have been known to use a short storm drain culvert to get to the other side of a highway, those culverts are often filled with rain water the same time the turtles need to cross. The corrugated steel culverts also present issue because the metal ridges are difficult for animals with short legs to navigate.