The Carlisle Mosquito Online

Friday, January 26, 2007


Leave it to the beavers, or co-exist?

The beavers on the Docktermans' pond toppled these trees near the dam. They chewed as high as they could reach, about two feet high standing on their hind legs. (Photo by Gabrielle Dockterman)

Faced with rising water levels that threatened our property off Russell Street (see last week's Mosquoto, page 1), w knew we had to do something aobut the beavers that were expanding our pond. What could we do?

In Massachusetts, it is illegal to relocate wild animals. If you trap beavers, you have to kill them. So our choices were to kill them or try to coexist with them. In educating myself about beavers I learned that they are peaceful, family-oriented, clever animals. Although they are the largest rodents in North America, they are hardly vermin. Beavers play an important role in our ecosystem. The wetlands created by their dams provide habitats for many species of animals and plants. We were already witnessing an increase in biodiversity of wildlife (recent spottings include mink and possibly a fisher cat). Trapping would only be an interim solution anyway, because new beavers would likely discover the pond in a year or two.

After doing some research into possible ways to coexist, I learned there are several strategies to address the problem, depending upon the particular situation. Breaching the dam does not work because beavers inspect the dam every night for damage and repair it immediately. Also, the sound of running water stimulates beavers to increase damming activity.

I contacted a company called (what else?) Beaver Solutions. The owner, Mike Callahan, came to assess the situation. We went out on the kayaks and Mike pointed out various signs of recent beaver activity. Most of the sticks in the dam had no bark because the beavers had eaten it. Nearby were stumps with the telltale chewed points that the beavers had gnawed to fell the tree. He noticed one such tree caught in the branches of another tree. "Too bad," he chuckled. On my quizzical expression he explained that the trees don't always fall the way the beavers want, and this one got stuck.
Mike Callahan of Beaver Solutions (foreground) and his assistant Scott Bradlee move the pipe into the pond. Note the wire cage to prevent the beavers from blocking the pipe. (Photo by Gabrielle Dockterman)

Beavers' appetite for trees

I had been wondering why the pond had grown so drastically this year. Mike explained that beavers eat only certain trees and plants (birch, maple, aspen and willow are among their favorites). When those are depleted at the shoreline, the beavers increase damming activity to flood the area, giving them access to more food. Since they feel safer in water than on land, and since heavy trees are easier to move by floating them in water, they need their food to be close to or in the water.

Mike recommended that we install a special pipe through the dam to lower the water level. A pipe can be a permanent solution only if the beavers cannot detect the flow of water into the pipe. The 15" diameter pipe would be very long, with large cages at both ends to prevent the beavers from blocking it. Mike estimated that this flow device would lower the water level 12" in the fall, and could be adjusted in the spring to lower it another six inches if we so desired. Lowering it too drastically all at once could spur the beavers to increase damming nearby.

Obtaining permission

This all seemed to make sense, so we applied for the necessary permits with the Board of Health and ConsCom. I took photos and prepared a presentation for the board meetings. I researched who owned the section of dam we would be disturbing, and let the neighbors know what we would be doing.

I have been referring to "our" pond all along, but in fact several different properties include a piece of this pond. One of our abutters didn't even know there was a pond back there(!) so I encouraged them to explore it. In Massachusetts, the surface of waterways belongs to the Commonwealth; as long as you are floating, you are not trespassing. However, the dam itself is not on our property, and it would be much easier for Mike to access the dam from land. Fortunately, the owners all gave us permission to do the work and graciously let us drive across their field to access the dam.
The crew from the National Geographic Channel are (left to right), sound recordist Rob Maerz, field producer Cassie Rowland, director/cameraman Ben Rowland, and Mike Callahan. At their feet is one section of the pipe they installed. (Photo by Gabrielle Dockterman)

A request to film

Meanwhile, Mike had been approached by a TV producer looking to do a story on beavers for an episode of "Animal Extractors," a television series about dealing with nuisance wildlife that airs on the National Geographic Channel. Mike asked if we might be willing to have them shoot here when he installs the pipe. Ours would be one of several properties the film crew would like to consider, and would we be willing to let them come take a look?

That weekend I watched the season premiere episode that followed the "extraction" of a family of raccoons living in someone's attic. It was well done, so I agreed to let National Geographic come and scout our location. They ended up choosing our property.

By then we had been granted a Ten-day Emergency Beaver or Muskrat Permit from the BOH, and the required WPA (Wetlands Protection Act) Emergency Certification from ConsCom for the month of November. This would allow us to breach the dam, install water flow devices and hire a licensed trapper if we wanted.

The big day

On November 9, 2006, Mike arrived with his assistant and the film crew to install the pipe. When I agreed to do this, I didn't realize that I would be on camera. In addition to filming the installation of the pipe, Mike and I had to reenact our initial meeting and exploration of the pond (so much for "reality" TV!). It was a very small crew: a British husband and wife and a local sound recordist. They shot in high definition video, adding an infrared package at night to capture the nocturnal beavers.

The crew filmed us setting out on the kayaks from our house. Our dog will be the real star of the show in his little life vest, leaning forward eagerly like a masthead on the kayak adventure. After a few takes, they directed us to paddle across the pond and in a few minutes they would join us on the other side by the dam.

While we were waiting, we paddled around looking for signs of beavers for them to film. At one point I thought I had found the beaver lodge, but Mike determined it was a "scent mound" created by the beavers to mark their territory, warning other beavers that the pond is already occupied. We found several of these small mounds of mud, sticks and leaves around the periphery of the pond.

The beaver lodge

Affordable housing for a beaver family? This lodge upstream from the Docktermans' dam is six feet high, built of sticks and branches. (Photo by Gabrielle Dockterman)

It took the crew a while to set up, so I decided to explore a new area of flooded woods upstream from the dam. When I stumbled upon a six-foot high mountain of sticks and branches, I knew instantly that this was the beaver lodge! Excitedly I called to Mike. Of course, when the crew was ready I had to excitedly call to Mike again to reenact the discovery for the camera.

The lodge was constructed at the edge of the pond. Beaver lodges usually have two underwater entrances so that if an otter or other predator comes in one entrance, the beavers can flee out the other. They live in the lodge all winter, occasionally venturing out under the ice to retrieve sticks they have cached nearby as food. They live in a hollow space above water in the top of the lodge. In the winter it is sometimes possible to see steam rising from vents in the top of the lodge from the beavers' breath inside. Mike estimated that a family of five to eight beavers would be a typical number living in a pond of this size, likely two parents and two generations of kits.

After all this excitement we nearly forgot the real reason Mike was here: to install the pipe through the dam. The crew filmed every step of the complicated process.

The water recedes — somewhat

Taken this week when the weather turned wintry, this photo shows the pipe encased in ice. Water still gushes from it. (Photo by Gabrielle Dockterman)

When Mike installed the pipe, he also put a large breach at the other end of the dam, both to distract the beavers from the pipe and to help lower the water level. The water went down about eight inches over the next few days, so we were encouraged. Then it rained and the water level started to creep back up. Mike came back and lowered the pipe six more inches, hoping that would lower the water the desired 12 inches. Part of the problem is that in the fall the trees go dormant for the winter and stop taking up water, which then has nowhere to go except through that pipe.

Though water continues to gush out of the pipe, the water level is currently only about three inches lower than its highest point when our basement flooded. The trees are still submerged. To provide another frame of reference, at its highest point the water's edge was six feet from our well head. After the pipe was installed, the water initially receded to a point 17 feet from the well. It is currently nine feet away. When the basement flooded, the water's edge was 26 feet from that end of the house. It is now 40 feet away. Although the pipe has not worked to our complete satisfaction yet, most certainly we would be flooded without it.

Mike believes he underestimated the inflow to the pond, which is fed by several streams. He will return in the spring to lower pipe again and possibly install an additional pipe through the dam. Dropping the water level further now could kill many animals that have burrowed into the mud in shallow areas to spend the winter.

Boomer Dockterman supervises the action from his perch on one of the kayaks. All seems to be going well. (Photo by Cassie Rowland)
Maybe some of you are rolling your eyes now and wondering why I just don't trap the darn beavers and make myself a nice fur coat. To you I say: this is Carlisle, after all

The TV episode will likely air toward the end of the 13-part series. Watch the Mosquito for the airdate, or check

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