Beavers are plentiful at Moosehorn National Wildlife Refuge in eastern Maine. While they often create excellent wetland habitat for migratory birds, beavers sometimes create management challenges by their proclivity to raise water levels (photo by A. Weik, USFWS).

Biological aide Jill Barschdorf inspects progress on a "Beaver Befuddler" fence and pipe project at Moosehorn National Wildlife Refuge, Maine, during September 2007. Refuge staff use fenced exclosures at water control structures to reduce maintenance costs and enhance control over water levels to provide wetland habitat for migratory birds (photo by A. Weik, USFWS).

Beaver exclosure installed at Moosehorn National Wildlife Refuge, eastern Maine, August 2007. A fence made of concrete reinforcing wire keeps beavers from plugging the water control structure. Beavers may dam against the fence, but corrugated PVC and foundation drainage pipe allow water to flow through the outlet normally (photo by A. Weik, USFWS).

Buoyed by success a year ago of a project to reduce maintenance costs of keeping a water control structure free of beaver dam material, staff at Moosehorn National Wildlife Refuge installed fencing and drainage pipe at four water control structures that had a history of being plugged by beavers.  The beavers' activity at the outlets of these impoundments had raised water to a level that reduced the amount of emergent vegetation in the wetlands, and threatened the stability of downstream refuge roads.  By installing beaver fencing to exclude beavers from the water control structure at the wetland outlet yet allow outflow through the installed pipes, and by allowing regulated trapping, we hope to reduce maintenance costs and  provide high quality habitat for migratory birds, beavers, and other wildlife.

The fencing projects were accomplished during August and September, 2007 by various combinations of refuge staff, biological aides, YCC crew, and STEP students.  Heavy equipment operator Bill Jones and maintenance mechanic Mike Krug used the refuge's backhoe to set some of the galvanized metal posts for the fence structure.  Observations over the next few weeks indicated the beavers had not been able to affect the function of the half circle riser water control structures, and we have been able to maintain the wetlands at our objective water levels.  

One year after the first "Beaver Befuddler" fence and pipe project was completed, the water control structure has required no maintenance.  Beavers have dammed against the fence exclosure, but drainage pipe placed through the fence has allowed water to flow normally.  Our ability to regulate the water level in the wetland resulted in an excellent stand of wild rice that was fed on extensively by wood ducks, black ducks, and black birds. 

In addition to the four fencing projects at water control structures completed this summer, we proactively installed drainage pipe to prevent flooding at two beaver dams on a stream that were unoccupied this year.  In recent years beavers at these two sites on Moosehorn Stream had raised water to levels that provided excellent habitat for migratory birds, but threatened the integrity of a nearby railroad bed.  We took advantage of the current absence of beavers to complete the project, and used a laser level to set the elevation of the drainage pipe in the beaver dam to set a limit on the high water mark of the flowage.  We anticipate that beavers will re-inhabit the stream and once again create a highly productive wetland.  Stay tuned.