The Basics of Electric Fencing

for Deterring Grizzly and Black Bears

By following best practices, a properly designed and constructed electric fence can be very effective at excluding grizzly bears and black bears from human areas and preventing conflicts.

There are various fence designs and ways to use electric fencing for deterring bears. Electric fences can be designed to be a permanent fence, or temporary, allowing for portable or seasonal use. It can be used to protect livestock, including for around chicken coops; goat, sheep, and pig pens; calving and lambing grounds; night pens; and larger pastures. It can be used around residential yards, or to protect gardens, fruit trees, bee yards, or around larger crops and orchards. It can protect areas with stored attractants, such as garbage, livestock or animal feed, or any area you might be looking to keep bears out of or away from.

Fence design, voltage output, and correct grounding are three important factors to ensure the fence is effective in deterring bears.

How Electric Fencing Works

Electric fencing uses an energized power source (an energizer) to send pulsed electric current through wire, providing an electric shock to deter wildlife or animals from crossing a boundary. When an animal touches the electrified wire, the electric current passes through the animal, into the soil, and is gathered by a ground rod system and diverted back to the energizer. In order for an animal to receive a shock, the electric current needs to find its way back to the energizer to complete the circuit (Figure 1).

Figure 1. An all-hot (live) wire electric fence. When a bear touches an electrified wire, the electricity travels through the animal, into the soil, to the ground rod, and back to the energizer, completing the electrical circuit, which delivers the shock.

A good grounding system is essential to any electric fence to ensure the electric current completes the circuit back to the energizer. For small-scale fences and areas with sufficient soil moisture, an all-hot (live) wire electric fence with a ground rod system can be sufficient to deter bears. For areas with drier soils, like the Rocky Mountain West, or for larger fence projects, the soil conditions may be not ideal to carry the electric current back to the energizer to deliver an effective shock. In this case, you can use a ground-return fence design, which includes a ground wire in the fence (Figure 2).

Figure 2. Alternating hot (live) wires and ground wires in an electric fence. When a bear touches an electrified and ground wire simultaneously, the electricity passes through the animal, and back to the energizer through the ground earth system.

Fence Design and Wire Height Recommendations

Fence design is one of the important components to ensure an effective fence for deterring bears. Wire height and wire spacing are two important parts to an effective fence design.

Wire Height Specs

The lowest hot wire should be no higher than 6-8 inches off the ground, or a bear may be tempted to dig under the fence. If existing fence has welded woven wire or barrier, the lowest wire can be adjusted up to 10 inches.

The highest hot wire should be at least 36-48 inches tall.

Wire Spacing Specs

Spacing should be no greater than 10 inches between wires. If existing fence provides a barrier (i.e., woven wire), electric wire spacing can be adjusted from this rule.

Voltage Output

When choosing an energizer, check to be sure it meets the minimum specs to deter grizzlies.

  • Joule rating: 0.7-1.0 stored joules or higher

  • Output joule rating: 0.5-0.7 output joules or higher

  • Pulse rate: 45-60 pulses per minute, or once every 1.0-1.5 seconds

Correct Grounding

The grounding system is a vital component for an effective electric fence. To complete the electric circuit, electricity must return to the energizer. This is accomplished with a grounding/earthing system. A grounding system in the soil attracts and gathers the flow of electricity and delivers it back to the energizer. For an electric fence to be effective, a grounding system must be big enough in relation to the energizer and soil moisture conditions.

Correct grounding should allow for 6-8 feet of galvanized or copper ground rod per 1 joule of energy in energizer.