Effectiveness of Modifying Existing Fence to Prevent Ungulate Use of High Value Pastures 2005

Introduction

Deer (white-tailed deer, Odocoileus virginianus and mule deer, O. hemionus) and elk (Cervus elaphus) in Montana and other areas of the intermountain west cause considerable monetary losses as perceived by some farmers and ranchers (Conover 1984, Wywialowski 1994, Irby et al. 1997). Big game animals caused an average monetary loss of $5,616 in forage consumption per landowner in southwest Montana in 1993 (Lacey et. al. 1993). Financial losses due to wildlife lower landowner tolerance of wildlife on their property (Conover, 1998). In other states, compensation programs exist to replenish losses accrued by rancher for wildlife forage consumption, but these program are increasingly costly and do not satisfy all producers (Van Tassel et. al. 1999 and Wagner et. al. 1997).

Many methods of preventing damage by ungulates have been used. Chemical scents, frightening, hazing, trapping, and localized shooting are current methods. Results vary, and many of these methods provide only temporary relief with each application. Habitat alternations to encourage ungulate use of different areas can be effective but is often costly. Fences provide the most consistent long term control compared to other deterrent methods, but are costly to erect (Craven 1983, deCalesta 1983). Many designs of woven wire and electric fences are currently used. Costs of erecting deer proof fencing could be greatly reduced if an existing fence can be modified instead of being replaced entirely. Modifying fences could be made a more cost effective means of controlling ungulates use. No information currently exists on how density of ungulates affects a fence’s effectiveness to deter deer or elk.

Objectives

This study will investigate the possibility of modifying existing fences to prohibit deer and elk crossings. Currently, no literature exists on the cost or effectiveness of such fences for deterring deer and elk. The objective of this study will be to determine the cost and effectiveness of fence modifications in terms of effectively reducing the number of deer and elk that penetrate them.

A simple method will be developed to help ranchers determine the cost effectiveness of fencing on their ranch. A simple procedure to measure forage loss to deer and elk using exclusion cages and the cost of fencing to eliminate that forage loss will be described in all project information materials.

Study Areas

Formal testing of high-tensile and net-wire fence designs is taking place on ranches in south central and southwestern Montana. Four individual replication sites for deer and four for elk are being used. Sites where designs are being tested with deer are near Livingston and Two Dot, and locations for testing with elk are near White Sulphur Springs and Cameron.

Methods

At each site, five individual standard four-strand barbed wire fence exclosures were constructed. Each exclosure was 32 feet by 32 feet. Four exclosures were then randomly modified to one of four selected types, with the fifth left as a control. In all modifications, 3/8 inch rebar was used to extend the height of the posts to six feet three inches. Modification one consisted of adding a single strand of 12-gauge high tensile wire between each existing wire and between the bottom wire and the ground. Three strands of 12-gauge high tensile wire were added above existing wire to bring the fence height to a total of six feet. Modification two was exactly the same as the first; except for the bottom four strands of high tensile wire were electrified with at least 4,000 volts of electricity. Modification three had 47-inch woven wire placed at ground level over the barbed wire, with three strands of 12-gauge high tensile wire strung above existing wire to bring the total height to six feet. In modifications one, two, and three, the rebar was bent at approximately a 45-degree angle to the outside of the exclosure. Modification four had 39-inch woven wire placed at ground level over the barbed wire, with 32-inch woven strung above to bring the total height to five feet eleven inches, with the rebar left straight. Six bales (approximately 400 pounds) of high quality alfalfa hay were then placed inside each exclosure as bait. Exclosures were monitored weekly to determine if deer or elk entered them.

Results

The testing is between the first and second year so results are preliminary and represent only the first year data. Testing will begin again in October of 2005 and continue through March of 2006. Eighty-eight total breaches of each design were possible for both deer and elk during the first year of the study. For the designs in elk areas, the control was breached 21 times, the seven-wire non-electrified was breached once, the woven wire with high-tensile above was breached twice, and the seven-wire electric and full woven wire were not breached at all by elk. For the designs in the deer areas, the control was breached 55 times, the seven-wire non-electrified was breached 36 times, the seven-wire electrified was breached 26 times, the woven wire with high tensile was breached four times, and the full woven wire fence was not breached at all by deer.

Cost of materials to modify an existing fence using the seven-wire non-electrified design cost approximately $1,300 per mile. The same design with electrification cost $1,500 per mile. The woven wire-high tensile combination cost $2,600 per mile and the design made of all woven wire cost $3,500 per mile.

Preliminary results indicate effective modifications can be made to existing fences for $1,300- $3,500 per mile for materials. Traditional complete construction of game fences cost more than $10,000 per mile. These fences may be used in lieu of compensation programs for ranchers. Also, if farmers and ranchers can keep big game out of important foraging areas, their tolerance for these animals on the rest of their property may greatly increase.

The number of individual producers that may benefit from this study is entirely dependent on the unique circumstances surrounding each farm or ranch, but impact will likely be widespread.

Contact Information

James E. Knight, Professor and Extension Wildlife Specialist
Montana State University
Animal and Range Sciences Department
219 Linfield Hall
Bozeman, MT 59717
(406) 994-5579

Last Modified: 08/07/2006