Cary looks for peace with beavers

Rodents caused dam flooding

akenney@newsobserver.comDecember 4, 2012 

— The town of Cary is trying out a new answer to an age-old question: How do you stop a beaver damming?

It’s a challenge that’s dogged town staff since the summer before last, when the rodents flooded a new wetland on the southeast side of Bond Lake in mid-western Cary.

First the local government tried the traditional method: A contractor in February set traps for the beavers, but the town had them pulled amid outcry from residents and birders, who liked the new beaver pond.

Next came a non-lethal show of force, with the town destroying the beavers’ dam in the hopes that they’d just go away. Castor canadensis was back within months.

“They get upset and they rebuild,” said Carolyn Lewis, a stormwater specialist for the town.

She’s right – it’s in a beaver’s genes to turn streams into ponds and swamps.

Bust their dam, they’ll drag more logs into the river. Poke a drainage hole, they’ll fill it with mud. They hate the very sound of running water, and they’ll build until it stops.

Now the town is trying a new tactic that staff hope will subvert those natural instincts.

The idea of the $3,500 project is to let the beavers think their dam is working better than it really is. If it works, the “flow control device” will allow water to pass silently through the dam, keeping the water levels in check without alerting the beavers to the leak in their dam.

However, the town’s not out of the swamp yet. Installation of the pipe damaged part of the dam, by necessity, and drained the pond. The contractor did all the work by hand, hoping not to traumatize the beavers, but the semi-aquatic rodents haven’t yet returned to the site.

Lewis isn’t surprised the animals haven’t rebuilt their old stomping grounds yet.

“Not only have we unearthed their dams, but we’ve also exposed the holes in the side of the wetland where they stay,” she said. “We knew it would take weeks before the very first one would show up.”

The town may have to offer some encouragement if the beavers don’t show soon – a spray of scent from another beaver may inspire the Bond Park dam-builders to reclaim what’s theirs.

“That’ll really irritate them,” Lewis said.

Caroline Morgan, a local birder, is anxious for the repair of the little ecosystem tucked at the edge of the park.

“It’s pretty unique, just because of all the diversity,” she said, pausing from her photography near the dam. “The fact that the beavers turned this area into a swamp brought all kinds of animals here.”

Kenney: 919-460-2608 or twitter.com/KenneyOnCary

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