This week our wikipedia friend launched the first ever entry on effective tools for beaver management. It talks about flow devices and culvert protection, and emphasizes that trapping is a short term solution. It still needs photos to give it that “stop killing beavers and read me” touch, but its well on its way to being a permanent resource.
Beaver Dam Pipes
Beavers diligently plug leaks in their dams, because their survival depends upon the cover provided by the water in their pond. If a beaver can detect the flow of pond water into a pipe, it will plug the pipe with mud and sticks.
To be successful, a beaver dam pipe must eliminate the sound and feel of water flowing into the pipe. Successful pipe designs (e.g. Flexible Pond Leveler™, Castor Master™, Clemson Pond Leveler) achieve this by protecting the intake end of the pipe with a cylindrical fence enclosure. A beaver swimming along the outside of the fence enclosure is unable to hear or feel the flow of water into the pipe and cannot reach it to block it.
Photo: Mike Callahan, Beaver Solutions Flow device filter ready to be lowered into water
The pond level is controlled by the height of the pipe in the dam. Since beavers depend on water for their survival, the more a beaver pond is lowered with a pipe, the more likely it is that the beavers will try to build a new dam to return the water to its previous high level. In addition, the more a beaver pond is lowered, the more valuable wetland acreage is lost. Therefore, it is important to lower a beaver pond only enough to resolve the threat to human health, safety or property.
I like being able to see the roundfence up close. Ours suffered a bit in the last rain, and Mike says its essential that whatever happens the shape of the fence isn’t changed. Once beavers are able to feel the suction to the pipe they will find a way to dam it. They are also smart enough to learn that round fencing means leaks, and will dam any round-fence in the future too! Yikes!
Culvert Protective Fences
The ‘’’Beaver Deceiver™’’’ (a trapezoidal shaped culvert fence) was invented by Skip Lisle in the 1990s while working for the Penobscot Nation in Maine. It is very effective at completely eliminating beaver damming of a culvert. It works in three ways. First, the perimeter of the trapezoidal fence is typically 40 – 50 feet long, making it difficult for a beaver to dam the entire fence. Second, as beavers try to dam the culvert, the fence forces them to dam in a direction away from the culvert, which is not their nature. Third, as they dam further out on the fence, the opening the stream is flowing into is getting wider. Therefore, the damming stimuli of the sound and feel of moving water decrease the further they dam on the fence. If the sides of the fence are at least 12 feet long the beavers will generally leave the fence alone.
To be effective however, a culvert fence must be surrounded by enough water that the beavers will need to dam the entire fence perimeter. In areas where the streambed is narrow rather than wide, the fence must be narrow so that it is surrounded by water. Being narrow loses one advantage of the trapezoidal shape, but it can still deter beavers from damming the culvert. Since beavers are excellent diggers, a fence floor is always generally needed to prevent beaver tunneling under the fence. The fence walls only need to be 24 inches above the water line, since beavers do not climb.
Photo: Mike Callahan, Beaver Solutions Trapezoidal Fence to prevent damming of culvert
When I think of how hard we all worked to find information about beaver management back before the fateful meeting in November, I am very very pleased with this development. At the time I had three important sources of information: An article on the Clemson pond leveler, an article from Canada about the use of “Limiters” to regulate water height in Gateau park, and an article from the HAW River Assembly in North Carolina. Think about how different the world will be for the next starry eyed woman who wants to save beavers!
