A sign at the entrance for the Richardson Nature Center directs motorists on Bush Lake Road to slow down for turtles who may be trying to cross the roadway Thursday in Bloomington. (ANTHONY SOUFFLE, Star Tribune/The Minnesota Star Tribune)

The riddle isn't why the turtle crossed the road, but how to keep it safe from cars.

In Bloomington, where turtles trundle across Bush Lake Road in the spring and fall, moving between Hyland Lake and Bush Lake and the surrounding wetlands, that might mean installing a fence while the city and Hennepin County figure out if a special turtle tunnel might be feasible the next time the street is rebuilt.

The city is going after a $300,000 federal grant to build a foot-tall mesh fence that would stretch more than a mile on the edge of the Hyland Lake Park Reserve. It would replace a barrier made of landscaping fabric that seems to have kept turtles off the road. But the barrier is sagging and frayed after years of use, said Jack Distel, Bloomington's water resources specialist.

"We want to find some funding for a long-term solution," Distel said.

To build a permanent fence, Bloomington is pursuing federal funding for wildlife crossings, made available as part of the Infrastructure Investment and Jobs Act passed in 2021.

A four-year study by the Minnesota Zoo and the Minnesota Department of Transportation found fences significantly cut down on the number of turtle deaths — though some pushed back, including Scandia officials who said the fences are ugly.

Christopher Smith, wildlife ecologist with MnDOT, said the department is working on a standard turtle-protection fence that could be built anywhere state roads run through turtle habitats.

The area around the Hyland Lake Park Preserve is already a hot spot for turtle deaths because there are so many ponds and wetlands, Distel said, but roads have made it more dangerous for turtles to travel.

A fence along Bush Lake Road would keep turtles off the road, but it would also make it a lot harder for them to move around.

"It's a pro and con," Distel said. Fences can save turtles from being crushed by cars, but they do need to move around to eat and nest.

Eventually, Bloomington wants to see turtle crossings under some key streets like Bush Lake Road. Fences would not be made totally redundant, Distel said, but could help corral animals toward the culverts.

But Distel and Bloomington City Engineer Julie Long said tunnels will have to wait until the next time Bush Lake Road is rebuilt, and adding a culvert for animals to cross under the road will require buy-in from Hennepin County.

Turtles are worth all this trouble, Distel said, because they're an important part of watery ecosystems, eating dead and decaying plants and animals that could spread disease.

When turtles cross roads, they also present a danger to drivers, and to anyone who gets out of their car to help a turtle.

"Being Minnesotans, we're all pretty familiar with deer-vehicle collisions," Smith said. "But small critters, we don't typically think of them as being dangerous in that way."

Problems arise when drivers slam on the brakes or swerve for turtles in a way other drivers do not anticipate, he said.

Two types of turtles — Blanding's turtles and wood turtles — are considered threatened in Minnesota, and the U.S. Fish and Wildlife Agency is weighing whether to list both species as threatened.

Smith said preventing wood turtles and Blanding's turtles from dying on the road could prevent onerous federal regulations on road construction that could kick in if the turtles are listed as threatened or endangered.

And, Distel said, Bloomington just seems to like its turtles.

"Having this urban wildlife is a huge value for the city," he said. "We're happy to have them."