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Electric Breach Guard for Beaver

A fence energizer is a device that was designed to control livestock. However, it can also be used to keep beaver from repairing a breach in a dam by creating an electrified exclosure.

fence energizer

How it Works

A rigid main wire is suspended above the water on floats. Several short "dangle" wires hang from this main wire. These wires extend too within an inch of the surface. When a beaver swims up to inspect the breach in the dam, it will receive a shock when it touches one of the dangle wires.

Special Considerations

  1. The main advantage of the beaver shocker is that it is easy to install and is a fairly compact device to carry in the field.
  2. The device has to be checked daily after the installation until the beavers receive a shock and learn to leave it alone.
  3. Maintenance is minimal. The device must be checked for battery condition and to make sure there is no debris in the breach that might short out the system and shorten the life of the battery.
  4. Use only deep-cycle RV batteries. They are designed to be recharged many times without damage.
  5. The depth of the breach in the dam determines the depth of the water in the pond. If the water becomes too shallow behind the dam, beaver may try to build a dam around the upstream side to try to neutralize the device.
  6. Don't use fence energizers that utilize 120-volt house current. This will create a dangerous situation.

Materials (4.ft wide breach in a beaver dam)

  • Electric Shepard ES250 fence energizer which delivers 8000 kilovolts-no load and 1500 kilovolts-heavy load (a substitute energizer can be used as long as it is comparable).
  • 12-volt deep cycle battery 600 CCA (cold cranking amps) minimum
  • 4 - 6 ft x 5/8 in diameter fiberglass posts
  • 12 - 6 in x 4 in PVC floats with 3/4 in diameter hole
  • 16 ft 1/8 in diameter soft steel wire
  • 20 ft 14 gauge electric fence wire
  • 8 ft 1/4 in diameter (inside) rubber hose
  • Double insulated electric fence wire (length varies with individual applications)
  • Steel ground rod 3 ft to 4 ft in length
  • Box with lock to secure energizer and battery (optional)


Shocker construction: It is suggested that the shocker be constructed and assembled inside or at a shop and not in the field. For an illustration of how the shocker is assembled refer to the figure above.

  1. Cut the rubber hose into 5 in long pieces.
  2. Cut the 14 gauge wire into 18 in long pieces which are formed into straight pieces of wire 16 in long with a 3/8 to 1/2 in diameter loop formed on the end.
  3. Form 4 loops 1 1/2 inch to 2 inch diameter in the 1/8 inch diameter Wire using the dimensions from the attached diagram. As you form the loops be sure to slide the correct number of dangle wires and spacers before forming the next loop. The first loop to be formed will be an end loop and then add the appropriate number of spacers and dangle wires. The next loop is formed and more spacers and dangle wires are added. It is important to use the correct number of spacers and dangle wires and in correct sequence. Also, the distance between the loops must be of sufficient length so that the dangle wires move freely and don't bind against the rubber spacers. After the fourth loop is formed, cut the excess wire off, but leave a short end to which you attach the hot wire from the energizer. An easy way to form a loop in a wire is to wrap the wire around a cylindrical object which is of the desired diameter. It is also easier if the cylinder is clamped in a vise.

Shocker Installation

The figure at the top of the page shows what the shocker should look like in a dam.

  1. Breach the dam to the desired dam height with the width of the breach 1 ft less than the width of the shocker.
  2. Install the two posts closest to the dam With the breach centered on them. They should be close enough to the dam so that the beaver cannot swim around the end of the shocker but far enough away so the floats will move up and down freely. You may have to make a sump around these posts so that they can move freely. Place 3 floats on each post.
  3. Place the shocker on the two posts closest to the dam and use the shocker as a guide for the installation of the two other posts w/floats. Try to keep the posts plumb.
  4. Check the dangle Wires to make sure that they move freely and are above the water at least an inch.
  5. Drive the ground rod into the dam preferably in the water and as close as possible to the area where you will set up the energizer and battery.
  6. Connect the shocker to the energizer using the double insulated fence wire. I used a compression sleeve to connect the wire to the shocker, but use whatever works for you.
  7. Connect your ground \wire to the ground rod.
  8. Connect the battery to the energizer.
  9. Turn the energizer on and test the shocker to make sure it is working. An inexpensive tester can be found at most farm retail stores.
  10. Be sure that the floats move freely and that the dangle wires are not touching the water.
  11. If there is a problem with security, construct a box big enough for the battery and energizer out of plywood and lock it and chain it to an immovable object.

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  • NYSDEC Fish and Wildlife
    625 Broadway
    Albany, NY 12233-4750
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