Shocking Solutions to Bear Conflicts *
A Primer on Electric Fences
**New: How to build a simple electric predator fence
For the quick and easy set of instructions for construction of a simple predator electric fence, please click here:Constructing a simple electric predator fencebooklet.pdf
Electric Fences Make For Good Bear Neighbours
An electric fence has the power to keep bears out of landfills, apiaries, cabins, campsite, campers, livestock enclosures, gain sheds and just about anywhere else you don't want bears to go.
Today there are permanent fencing systems powerful enough to successfully keep grizzly bears out of a landfill. There are portable electric fences that can be set up and functional in less than two hours, and solar-powered systems that can be installed anywhere there's enough sun to charge the batteries. There are even lightweight, battery-powered fences that weigh less than 4 pounds (1.8 kg) and cost under $300 CDN that can protect a 30 foot X 30 foot (9.1 meter X 9.1 meter) camp site.
In the North Kootenay Lake area and the community of Kaslo, electric fencing installed through the North Kootenay Lake Bear Smart Program has been effectively used to prevent conflicts between both black and grizzly bears and fruit trees, chickens, hogs, and other small livestock.
Permanent Electric Fencing
Once properly installed, a permanent electric fence can be left in place for years. Permanent fences require less maintenance and stand up to environmental stresses like snow loads better than portable fences. You can also tighten hi-tensile loads better than portable fences. You can also tighten hi-tensile wire to 200 psi - when a bear pushes against the wire, the tension separates the bear's fur and the wire can deliver a shock right to the skin.
Permanent fencing makes sense for landfills, especially if bears are already conditioned to regard the area a food source. Camps, feed storage sheds, livestock pens, small orchards and gardens, and cabins in areas with along track record of bear-break-ins are also good candidates for a permanent electric fence.
Portable Electric Fences
Portable electric fences are great when you need temporary protection, like during lambing season. Or for apiaries that move hives to take advantage of pollination. Or even temporary back country camps. There are two main types of portable electric fencing designed to deter bears. One is a positive system; the other is an alternating positive/negative system.
A portable positive system normally consists of four strands of shock cord; 14 or 16 gauge wire stretched to 20 psi of tension. This type of fence is most often used at apiaries, small camps and to fence off gardens or fruit trees.
A portable six-strand light gauge wire system can be used in areas without good grounding, like dry gravel. Install a wire mess apron on extremely dry land, and spread calcium chloride around the fence to increase grounding during dry periods.
There are two proven systems that have been developed for temporary electric fences. A 30-foot X 42-foot (9.1 meter x 12.8 meter) electric fence can hold 32 bee colonies and costs about $300 to install. You can make a temporary fence out of electro-plastic netting, electrified twin or hot tape attached to posts or trees. Costs range from $200 for hot tape to $750 for electroplastic netting. As usual, you get what you pay for.
How An Electric Fence Works
An electric fence acts like an open circuit, with repeating pulses of electricity produced by the energizer flowing through the charged wires of the fence. When something touches a charged wire, it grounds the fence, creating a closed circuit - and a shocking experience for whatever's on the other end of the wire.
How Much Voltage?
You can't have too much, only too little. Bears have heavy fur, very thick skin, a high tolerance for pain and heavy foot pads that minimize grounding. This is one reason that an alternating ground wire configuration is recommended. Because they have big thick fur coats and insulating layers of fat, the latest recommendations suggest a minimum of 6,000 volts to effectively shock a black bear.
Components of an Electric fence
- An energizer operated by a solar module, a battery or plugged into a 110-volt outlet delivers the power.
- Live wire or wires of high tensile steel carry the pulses around the area being protected; 11 - 14 gauge wire with a minimum tensile strength of 200,000 psi and a minimum breaking of 1,800 pounds if recommended.
- Fencing posts made of treated wood, cedar, steel or fibreglass.
- High quality fence chargers. Use a 110-volt outlet or 12-volt deep-cycle marine batteries connected to a high-output fence charger approved by UL or the Canadian Standards Association (CSA). One recommendation is to use RV batteries, because they're designed for continuous operation and suffer no ill effects from being repeatedly run down and recharged.
- A grounding system that starts at the energizer, with low-resistance ground rods which go along the fenced area.
- Insulation to protect the live wire from accidental contact with the ground, which would short it out and “turn off” the fence.
- Tension springs or long stretches limit the mechanical tension in the wires, which contract when air temperature drops.
- Lightning protectors to protect your investment from lightning strikes and induction from power lines.
Installing A Permanent Electric Fence
Here's is the recommended installation of a permanent electric fence.
- Drive the corner posts and remove grass and weeds in an 18-inch (46-cm) strip along the fence line.
- Spray the cleared area with a herbicide to prevent re-growth; don't spray wider than 18 inches (46 cm) because the bear will be better grounded if it's standing on grass.
- Use four strands of polywire or electronet at 4, 16, 26 and 36 inches (10, 40, 66 and 91 cm above the ground. Stretch the wired to eliminate sagging. Use stones or weights to keep the wires at the correct heights when going over low areas.
- Leave extra wire at the knot so it can be wrapped around the lower wire to complete the circuit.
- Use a minimum voltage output of 6,000 volts. Verify your volt output with a voltmeter.
- Located the fence posts every 12 to 15 feet (3.65 to 4.57 meters) along the fence line, and install the insulators and wires. Wires have to be able to slide freely through insulators on fence posts.
- Put your battery in a water-tight container inside your enclosure, and energize all the wires.
- Every half-mile (.80 km) of fence line, drive four to six ground rods 5 to 7 feet (1.5 to 2.1 meters) deep into moist soil. In very dry, sandy soil or on rocky ground, grounding can be increased by laying grounded chicken wire around the outside perimeter of the electric fence - the predator will be standing on metal when it touches the hot wire.
Baiting The Fence
It is generally not smart to lure wildlife to places you want them to stay away from. But if you know bears have been visiting or likely to come around, baiting increases the odds the bear's sensitive nose, lips or tongue will come in direct contact with the hot wire and the resulting shock will send the bear on it's way. If you decide to bait, try raw bacon dipped in honey, molasses, or sardine juice, aluminium foil strips smeared with peanut butter or tins of salmon or tuna with a hole punched in them.
Anything that comes in contact with a charged wire can create a partially or completely closed circuit, including fallen trees or branches, blowing vegetation, or other animals like raccoons or deer. Routine maintenance is the key to keeping an electric fence in top shape, because if a downed tree branch closes a circuit, the fence is rendered powerless until the branch is removed and the circuit is open again. For the best performance, somebody should walk the fence line every day or two.
Grass or shrubs touching the wires draw down voltage; keep grass cut low under the bottom wire.
Make sure the wires are tight, and batteries are charged. DC chargers (6 and 12 volt) need their batteries recharged every two to four weeks.
Use at least a 70 amp-hour battery.
The fence charger should always be on. Check voltage weekly with a voltmeter. You should have at least 3,000 volts at the farthest distance from the charger. Always recharge during the day, so the fence is at maximum output at night, when bears are most likely to come calling.
Marine battery terminals and lead-composition eyelets resist corrosion. Keep your battery and fence charger dry and corrosion free. Disconnect lower wires if they're covered by snow.
Gates should be electrified, well-insulated and practical - they can range from single strands of electrified wire with gate handles to electrified panel or tubular gates. Some landfills install automatically closing gates to prevent wily bears from following vehicles into the landfill. Others find they can leave gates open during the day, as long as they're closed and fully electrified at night.
Whatever you do, don't make the mistake one person did and wire straight into the household current instead of using a fence charger. Households use continuous alternating current (AC) to power everything from lights to power tools, and it is always on. If an electric fence is plugged into an outlet, when someone gets zapped their muscles will contract and only partially release - making it very hard to let go, and pretty easy to get hurt.
Electric fencing combines high voltage with low amperage in a pulsating charge at 60-65 pulses a minute. When someone gets shocked, there's an involuntary muscle contraction. The pulsating charges give the person ¾ of a second to let go of the wire.
Getting zapped by an electric fence doesn't do any permanent damage to bears or people. But it's highly unpleasant, so put up a warning sign. In some municipalities, electric fences are illegal within city limits; be sure to check with your local municipal hall before installing one.
How To Get Fences
Many provincial agencies have diagrams, installation instructions and more on their Web sites. The Ministry of Agriculture, Food and Fisheries has an excellent set of instructions on electric fencing.
The folks at Premier Sheep are regarded as world leaders in electric fencing. You'll find a wealth of information and just about anything you could possibly want to order on their web site, including a handy chart that shows you what kind of fence to install based on what you're trying to protect.
Another company that sells and installs electric fencing is Margo Supplies, PO Box 5400, High River, Alberta T1V 1M5 Tel: 403-652-1932 Fax: 403-652-3511 E-Mail: email@example.com
Kid-Proofing Your Fence
People with kids who help tend the critters are often nervous about putting in an electric fence, and small children who get themselves tangled up in a fence can get a serious shock. One way to electrify a pen without electrifying kids is to use wooden posts for your fence posts; this allows a 4-inch (10 cm) separation between the inside wire and the outside wire. Use regular barbed-wire on the “outside” of the fence, at 12 inch (30 cm) spacing. Use the electric wire on the “inside” of the fence, also at 12 inch (30 cm) spacing, but set it in between the barbed-wire. Your outside barbed wire will be at 12, 24, 36 and 48 inches (30, 50, 61, 91 and 122 cm); your inside electric wire will be at 6,18,30 and 42 inches (15, 46, 76 and 107 cm). A child will encounter the barbed wire first; a predator will have to squeeze between the barbed wire, which puts its nose right in line with the hot wire. Install an electric cut-off switch at the gate to the pen or field, so when someone enters they can turn the power off.
* A Practical Guide to Bear Country - Living with Bears by Linda Masterson.
Electric Fence Suppliers
R & S Powerfence
645 Main Street
Penticton, BC V2A 5C9 Canada
Phone / Fax: (250) 492 7090
Kane Veterinary Supplies