Beaver damage concerns many landowners throughout our service area. The most effective lethal control techniques are trapping and night shooting. Although the two lethal control methods are effective, new beavers may move back into an area. Most beaver problems on our Headquarters Farm involve plugged overflow pipes and inlets which cause pond levels to rise over design levels, leading to erosion problems.
We use four methods to address this problem:
- night shooting,
- unplugging the overflow pipes or
- erecting exclosures around overflow pipes.
All of these require a certain amount of time. The third method, which involves removing mud and other debris from the overflow pipe, is the most time consuming. Two of our ponds on the Headquarters Farm have parallel-bar boxes over the inlets of overflow pipes. Parallel-bar boxes are constructed with 1-in. gaps between rods. Since these have been in place, beavers have built a dam around the sides of these boxes causing the pond level to rise.
This led us to the innovation of an electrical flotation device that deters beavers from plugging overflow inlets. It is constructed of 2-in. schedule 40 PVC pipe. The size of the flotation device is dependent on the size of the parallel-bar box. The key to making the flotation device work is to make it about three inches larger on all sides than the parallel-bar box itself. We used 1 in. x 4 ft. fiberglass rods for each inside corner of the flotation device to keep it in place and allow it to rise and fall with the water level.
The device can be powered by a portable energizer that uses six D-cell batteries and costs about $110.00. Battery life is three to four weeks. Another source of power is a permanent electric fence. When the flotation device is in place, beavers get an electrical shock when they try to dam up the parallel-bar box. In some cases the shock is enough to encourage beavers to leave the pond. A consistent power source is critical during late winter and spring when overflow cage inlets are flowing water. Within a few days after disconnecting the power source, beavers dammed around the parallel-bar box, covering the flotation device.
The flotation device takes about two hours to build. It has a capped PVC upright near each corner with two plastic insulators screwed onto the outside to attach polywire at heights of five and 10 inches from the water level. Once electrified, this prevents beavers from plugging the overflow inlet. The cost of building this device is about $33, not including an energizer (see table). It may be necessary to purchase an entire roll of polywire although only 40 feet is needed. With the flotation device in place, landowner time and labor as well as beaver damage is reduced.
Another application for electric exclusion is at a beaver dam. We break the beaver dam in the morning, dropping the water level within two to six inches above the channel bottom. At this point, we place a single strand of polywire three inches above the water supported by 3/8 in. x 4-ft. fiberglass rods. We run this wire the full length of the former dam. As beavers touch the energized wire they receive an electrical shock. This method buys some time and prevents beavers from damming the stream until night shooting or trapping can be conducted.
The methods outlined above can be used to help you battle beaver damage on your farm. Depending on your situation, one method may prove more useful than the other; however, in certain situations all four methods may be needed to deter beaver damage. None are foolproof and all require time and money.