Road Management & Engineering Journal
Road Management & Engineering Journal
Copyright © 1998 by TranSafety, Inc.
April 1, 1998
TranSafety, Inc.
1-800-777-2338
(U.S. and Canada)
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Guidelines for Controlling Beavers and Preventing Roadway Damage

The beaver (Castor canadensis) is North America's largest rodent and lives almost everywhere in the United States. Beavers have made a comeback after being trapped nearly to extinction at the turn of the century. Beaver management policy attempts to balance two points of view: those who enjoy beavers and those who consider them destructive pests.

The material summarized here comes from three sources: "Beaver Damage Control," Wisconsin Department of Natural Resources, Bureau of Wildlife Management (PUBL WM-007-96-REV); "Beaver Buster Confuses Critters," Peninsula Daily News, Monday, September 1, 1997; and "Beavers," by James E. Miller and Greg K. Yarrow, Prevention and Control of Wildlife Damage--1994, Cooperative Extension Division, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln.

Beavers are not aggressive animals; they put their energy into looking for habitat with a year-round source of water. They build dams to create bodies of water deep enough to support their lodges and store food supplies. Beaver ponds provide enjoyment for nature watchers, attract many wildlife species, and help prevent floods.

Some states protect beavers while others classify them as pests. These industrious creatures cause millions of dollars in damage annually. Their dams and burrows flood highways, collapse reservoir dams, and derail trains. Beavers can block a 12-inch culvert in twenty minutes.

OPTIONS FOR DEALING WITH BEAVER POPULATIONS

It's important to begin damage control as soon as a beaver problem appears. Once a colony becomes established, removing it is difficult and expensive. Also, some landowners refuse to allow beaver control on their property, causing beavers to return to adjacent areas.

Repelling Beavers

You can use commercial deer or rodent repellents for beavers--if the products are approved for use on vegetation. Also, you can manufacture your own repellants from soap, blood meal, moth balls, or rotten eggs. Success is limited, however, and all repellents wash away, so you must reapply them periodically.

Physical barriers--such as heavy wire mesh less than one inch in size, heavy-gauge hardware cloth, or tar paper--discourage beaver tree cutting. Size the protective material to a height of three feet, wrap it around the trees, and secure with wire.

Fences along the shoreline, including single-strand electric fencing, can keep beavers out of an area.

Discouraging Beaver Colonies

Reducing the desirability of an area, or undermining dams so they can't hold water, discourages beavers from building colonies. It also helps to eliminate the food trees that beavers prefer; less desirable alternatives are spruce and balsam.

A wildlife biologist in Maine suggests a "Beaver Deceiver" device on the upstream side of culverts. Wooden posts with sheets of wire fencing allow fish to get through but confuse the beavers. Beavers observed in Massachusetts could not get through the wire. Debris will collect along the fence, and beavers may attempt to build dams there, but removing these dams is easier than removing dams from inside the culvert. A sample culvert fence is shown below.

A fencing scheme to keep beaver from building dams inside culverts.
(Source: "Beaver Damage Control," Wisconsin Department of Natural Resources, Bureau of Wildlife Management.)

Beaver baffles installed at culvert entrances keep the beavers from getting inside. You may also need some kind of (human) theft-prevention device for the baffle. Some baffle designs are shown here.

Beaver baffles for preventing dams in culverts and for easier removal of dams.
(Source: "Beaver Damage Control," Wisconsin Department of Natural Resources, Bureau of Wildlife Management.)

Three-log drains, wire mesh culverts, and T-culvert guards extend through beaver dams to keep the water level low enough so it doesn't cause damage, or so the beavers get discouraged and move. Such devices vary in their success, since the sound of running water stimulates the beavers to plug the source of water drainage. Sample dam culverts are shown below.

Elbow extension and wire mesh culvert in beaver dams.
(Source: "Beaver Damage Control," Wisconsin Department of Natural Resources, Bureau of Wildlife Management.)

Culvert construction of #6 gauge reinforcing mesh panel (10' x 5' piece) covered with #4 gauge, 1"-2" welded wire mesh, attached with #1 hog rings. Bend assembled panel into a cylinder and fasten with #3 hog rings. Cover inlet end eith 6" x 6" wire mesh. Three sections (30') are considered a minimum length.

Another pipe design, the "Clemson Beaver Pond Leveler," is a perforated PVC pipe encased in heavy-gauge hog wire. Water drains from the pond without allowing the beavers to see, hear, or feel it, so they don't plug the dam. This device works best in relatively flat terrain. A list of materials and a diagram are given here.

TABLE 1
List of materials for the Clemson Beaver Pond Leveler.

Quantity Item
1 10' section, 10" diameter PVC pipe (Schedule 40)
1 PVC cap for 10" diameter PVC pipe (Schedule 40)
1 10"x8" PVC pipe reducer coupling (Schedule 40)
4 86" sections, 3/4" diameter plastic roll pipe (water pipe), 160 psi grade
4 3/4" metal couplings for roll pipe
16 1/4" x 2" galvanized eyebolts
16 1/4" galvanized nuts
16 1/4" galvanized washers
16 16" sections, 8 gauge galvanized wire (medium hardness)
2 96" sections, 2"x4" 1/2 gauge galvanized welded wire
2 lbs. Crab trap clamps (fasteners)
The above materials are required to assemble the intake device. The carrying pipe (flow pipe) may consist of 20 to 40 feet of 8-inch diameter PVC, Schdule 40 with coupling sleeves and elbows appropriate to the desired configuration.

Removing Beaver Colonies

Removing a colony is usually the last option, because it's difficult and expensive. Removal is often unsuccessful, since new beaver families may colonize a cleared area.

In Wisconsin, you may remove the dam with hand tools or a backhoe, or hire a licensed blaster. If you choose blasting in Wisconsin, you must first prove that the beavers have vacated their lodge, as you are not allowed to kill beavers with explosives. Wisconsin also requires written authorization to use explosives to remove a vacated lodge. Check the laws of your state for information on using explosives to remove a beaver dam.

Trapping, live or otherwise, may have limited success--although it is legal in some areas. Both the Wisconsin and Nebraska articles discuss trapping options and where to find further information. Shooting is an option in areas that allow it, but it may not be effective due to restrictions. If you trap or shoot, you must comply with all shooting, hunting, and trapping laws.

Various organizations offer nonlethal beaver control. Consult with local wildlife authorities for information.

Copyright © 1998 by TranSafety, Inc.



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