Wildlife-Friendly Fencing in Montana

Why do ordinary fences hurt wildlife?

FWP's guide lists the problem features: fences that are too high to jump, too low to crawl under, have loose or broken wires, have wires spaced too close together, can impale or snag a leaping animal, are hard for running animals or birds to see, or form a complete or three-dimensional barrier. Deer and elk most often catch their back legs between the top two wires while jumping.

The guide summarizes a Utah State University study of more than 600 miles of rangeland fence in Utah and Colorado. Researchers found on average one ungulate a year tangled per 2.5 miles of fence, most dying in the top two wires, with juveniles eight times more likely to die than adults and 70 percent of deaths on fences higher than 40 inches. Woven wire topped with a single barbed strand was the most lethal type. Fawns separated from their mothers by fences they could not cross were found dead beside fences, mostly woven wire.

What does a wildlife-friendly fence look like?

FWP's recommended livestock and wildlife compromise is specific. The top wire or rail preferably no more than 40 inches and at most 42 inches above the ground. At least 12 inches between the top two wires. The bottom wire or rail at least 16 inches and preferably 18 inches above the ground. Smooth wire or rail on top and smooth wire on the bottom. Preferably no vertical stays, or stiff plastic or composite stays if used. Posts at 16.5 foot intervals. And gates, drop-downs or other passages where wildlife concentrate and cross.

The guide says these standards will control cattle in most situations. Its three-strand smooth wire design puts wires at about 18, 28 to 30, and 40 to 42 inches on wood or steel posts 16.5 feet apart. Compare those numbers with Montana's legal fence definition, which requires a height between 42 and 48 inches for most types; our guide to Montana fence law explains why that standard matters if you are fencing out cattle.

What wire spacing works for cattle and wildlife together?

Where cattle are on the land year round, FWP's guide offers a four-strand barbed wire layout adapted from Wyoming Game and Fish: wires at 18, 22, 28 and 40 to 42 inches, which keeps 12 inches between the top two wires and 18 inches under the bottom, with a smooth bottom wire. It notes that most livestock pastures do not need a five or six strand barbed fence, and that a three or four strand fence, a mix of smooth and barbed wire, or high-tensile electric often does the job.

Sheep are harder because they need low wires, and woven wire, the usual sheep fence, is the worst for pronghorn and fawns. The guide's workaround is to raise the smooth bottom wire in selected sections so pronghorn can crawl under. For migration corridors it describes a drop-down top wire: one ranch hangs the top wire at 42 inches and lowers it to 36 inches in fall and winter so elk can pass. These are small changes to a fence you may already have.

Why does visibility matter so much?

Running animals and low-flying birds may not see a wire fence until they hit it. FWP notes that smooth wire, and high-tensile wire in particular, can be essentially invisible to animals. Its fixes: a top rail, small PVC pipe slipped over the top wire, flagging, fence markers, or high-visibility poly wire or tape on the top strand. It recommends black and white markers so the fence shows against both summer vegetation and snow, and says marking matters most in grasslands and near creeks and wetlands where grouse, owls, swans and waterfowl fly low.

A rounded top rail is preferred because it sheds snow; the guide says heavy snow buildup can deter elk and deer from crossing. That is one reason we often suggest a pole top rail on rural boundary fences, and it ties into our guide to snow and frost damage on fences.

How should a fence be placed on the land?

FWP says placement matters as much as design. Watch for daily and seasonal movement patterns and trails, keep swales, gullies and stream corridors open, and give wildlife access to water and riparian areas. Use tight exclusion fencing only where it is critical, such as gardens, orchards, children's play areas, kennels, haystacks, or calving and lambing pastures, and design boundary fences so wildlife can cross.

Slope changes everything. The guide illustrates how a 42 inch fence on flat ground becomes the equivalent of about 62 inches on a 30 percent slope and 75 inches on a 50 percent slope for an animal approaching from below. A fence that works on a valley floor can be a barrier on the hillside lots common above the Bitterroot. Where fences must cross slopes or follow ditches, drop the height there or add crossings.

Can you fix an old barbed wire fence instead of replacing it?

Usually. FWP's list for existing fences: keep wires tight, since sagging wire snares animals; replace barbed wire with smooth wire, especially on the top and bottom; lower the top wire to 40 inches, 42 at most; open the gap between the top two wires to 12 inches; cut the fence to three or at most four wires; add a top rail, visible top wire, PVC cover or flagging; and raise the bottom wire to at least 16 and preferably 18 inches. You can also convert only the sections where trails cross.

For seasonal passage, the guide describes drop-down top wires, lay-down fence sections, and gates left open when livestock are not present. The best fix of all, it says, is removing obsolete fences that are no longer needed. Old wire lying in the grass is also a legal matter in Montana, as our fence law guide explains.

What about fences around a house?

FWP's residential advice is short and worth following. Avoid fences with spikes, pickets or barbs that stick up above the top bar; deer judge a jump by the top horizontal bar and can be caught or impaled on decorative points. Use tall fences of any material only for small areas around the home, not as large perimeter fences. Space vertical bars or planks closely enough that animals do not try to push through. And remember that an animal that wanders through an open gate into a fully enclosed area may not find its way back out.

Many residential areas are in wildlife winter range, and the guide suggests landscaping or low, very permeable fences there. Where you must exclude animals from a small area, it recommends gates at corners so a trapped animal can find its way out. Local codes may also shape this: the City of Missoula, for example, limits deer garden fences to rear yards and requires a visible top rail; see fence height and permit rules.

What about open pipe posts?

This one surprises people. FWP's guide calls open vertical pipes, including hollow metal or PVC fence posts and gate uprights, silent killers of birds and small animals, which climb in and cannot climb out. The fix is simple: cap pipe posts, or fill them with sand, gravel or concrete, and use commercial caps on chain link posts. If your property has old open pipe posts, it is a quick job worth doing.

Is there help for wildlife-friendly fence projects?

FWP's guide says its Private Land Technical Assistance Program can contribute information, technical help and sometimes cost-share to projects that reduce wildlife conflicts on private land, and that NRCS offers technical and financial assistance for wildlife-friendly fence work through voluntary programs. The guide is from 2012, so program details may have changed; contact your local FWP office or NRCS field office to ask what is available now. FWP's current fence modification page still points landowners to the guide.

How HJ builds wildlife-friendly fences

We build post and rail, rail with smooth or welded wire, and ranch fences across Missoula and Ravalli counties, and we can build to FWP's heights and spacing, add a visible top rail, and leave crossings where your trails are. We also replace or rework sagging old wire; see fence repair. For styles, see split rail and buck-and-rail fences and horse fencing, and our custom fencing page for everything we build. This guide is part of our Montana Landscaping, Lawn & Irrigation Guide.

Call HJ Property Care & Tree Service at (406) 215-7319 or request a free fence estimate and we will walk the line with you.

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