Sometimes it’s best to let nature take its course.

That’s what Toyota Motor Manufacturing Mississippi environmental specialist Sean McCarthy learned when he and other team members tried to stifle the SimCity tendencies of some resourceful rodents.

During construction of the plant, two retention ponds were established. The ponds are designed to capture and hold storm water runoff, allowing any suspended solids to settle. Water discharge from the pond is regulated with an 11-foot sluice gate and seven-foot concrete wall just beyond the gate. When the gate is raised, the water flows out through three slots in the wall.

Except when beavers dam it.

“They packed the flow slots with trees and mud. It was almost like concrete,” says McCarthy. “We’d be down there once or twice a week and they’d be right back the next week.”

After battling the beavers for six months, the team packed it in by the fall of 2012. And the water stayed.

“It never empties,” McCarthy says. “Even in July and August there’s one to two feet of water. But there isn’t a risk of flooding since water still discharges when it reaches the top of the wall.”

The resulting lake brought other critters. Ducks, as well as fish and other species, now call it home.

It also helped the plant achieve certification as a Wildlife at Work program by the Wildlife Habitat Council and be named a finalist for its Rookie of the Year award this year.

“We’ve seen geese, crane, heron and fish,” says McCarthy. “Letting the beavers do their thing created this habitat.”

To discover more about Toyota’s biodiversity efforts, flock to its 2014 North American Environmental Report.