Outfoxing the Beavers

And other improvements at Spirit Springs Sanctuary

Does the sound of running water make you so crazy that you have to drop everything and find the leak right now? If this is you, chances are you’re a beaver!

Beavers build dams of mud and sticks to create ponds – safe havens where they can live, feed, and raise their families. But the sound of trickling water tells a beaver that its all-important security system has a hole in it – and the energetic rodents seem unable to rest until they’ve fixed the dam leak.

The large pond at Spirit Springs Sanctuary in Cass County has its resident beavers and visitors can sometimes see the marks on trees that they have gnawed. The pond’s outlet on the northeast end flows through a pipe under the trail to the buttonbush swamp, then slowly makes it way out to the huge marshland on the preserve’s north border. Though the flow is rarely fast, it’s strong enough to worry the pond’s beavers! Their energetic efforts to block the outflow pipe began to wash out the hiking trail and negatively affect other wildlife. They plugged the pipe so often that volunteers sometimes had to remove their work on a daily basis!

While it is sometimes necessary to eradicate beavers that are causing property damage, SWMLC staff didn’t want to do that, as we feel the beavers are part of Spirit Springs’ ecosystem. So we decided to trick them instead.

We developed a plan with our conservation partners at US Fish and Wildlife Service (USFWS), but we weren’t in a financial position to move forward until last year, when Cass County 100+ Women Who Care graciously donated $3,875 toward the project. Wanting to make their generosity go even further, we secured financial help from USFWS and Ducks Unlimited. Then supporters of SWMLC’s Birdathon Team, the Land Larks, raised another $3,211 this spring – enough money altogether that we could not only have the beaver deceiver installed, we could also make improvements to Spirit Spring’s driveway and parking lot.

The work was done this past June when contractors from Generation III Construction installed a brand-new beaver-resistant pond overflow at Spirit Springs. They dug up part of the trail and buried a long plastic pipe that extends underwater into the pond under a pile of limestone rock.

The pipe has a cap at the end and is perforated with many small holes along the sides. This allows water to seep in slowly from many places at once, eliminating that triggering sound that launches beavers into action and making it harder to plug multiple openings if they are attracted to it. The water exits on the other side of the hiking trail, covered by a cage that prevents debris and critters from getting in.

The contractors created limestone ‘check dams’ along the streambed that will prevent erosion by slowing the pond’s outflow to the buttonbush swamp during storms or other highwater events.

They also buried a 5’ tall water control device called an Agri Drain in the rocks beside the trail. This ingenious device will allow Stewardship staff to control the pond’s outflow by inserting panels of increasing heights.

Generation III didn’t stop there . . . they also graded the gravel parking lot and pushed the edges back – and they fixed the driveway, filling in the potholes and improving the drainage.

SWMLC’s Stewardship Crew will be back at the preserve later this summer and fall to work on more trail improvements that will address erosion issues on high-use trails and allow users to walk through wet areas elsewhere on the preserve where beavers are again busy at work!

We are very grateful to the Cass County 100+ Women Who Care for kicking this project off and supporting our efforts!



We also could have not done this work without our conservation partners at the US Fish and Wildlife Service, who designed our pond overflow. These ongoing improvements will make an impact on everyone who loves to visit Spirit Springs Sanctuary to enjoy its quiet solitude, variety of trails, and great plant and animal life.

Photos, Dave Brown unless credited otherwise
Story, Amelia Hansen