Born to roam one of the largest intact ecosystems in the temperate zones of the Earth, Wyoming’s wildlife often encounter a web of fence lines along their journeys. These fences can be deadly. Animals get caught up in the wire and die. Others are displaced and their migration patterns disrupted by impenetrable barriers in their paths.

Land managers admit that fences are a serious concern for wildlife. Both federal and state agencies now have fence standards to protect free-ranging wildlife migration routes. As part of the Restoring Wild Patterns program, the Wyoming Outdoor Council wants to increase open space for free-ranging healthy wildlife populations in Greater Yellowstone Ecosystem by identifying and removing fences that block wildlife migration routes.

What makes a fence wildlife friendly?
The “ideal” fence, from wildlife’s point of view, can be seen on approach so that it can be leapt over or crawled under without injury. The currently accepted wildlife-friendly fence standards are: three strands of wire with the bottom strand a smooth wire at 16", the second strand barbed wire at 24", the third, barbed wire at 32", and a pole on top at 40".

In 1990-92, the University of Wyoming’s Spatial Data and Visualization Center digitized fence data in cooperation with the University of Wyoming Cooperative Fish and Wildlife Research Unit and the Wyoming Game and Fish Department. They created a database that includes locations and descriptions of wire fences constructed for public lands livestock grazing and rights-of-way throughout southwestern Wyoming. Encompassing an area of over 36,000 square miles, the lands surveyed contained more than 1,600 livestock and roadway fences. These fences stretch thousands of miles across the landscape. Most of them do not meet wildlife-friendly fencing standards.

What happens with fences that aren’t “friendly?”
Wyoming Cooperative Fish and Wildlife Research Unit studies show that pronghorn select home ranges where fence densities (particularly woven wire) are lowest in order to minimize the number of fences they have to negotiate in search of forage or during migration. The consequence of this behavior is that fences are causing pronghorn ranges to shrink.

Other unfriendly fences entangle animals or intentionally create an impenetrable wall to keep livestock in or wildlife out. Together these fences permanently change where the animals roam in search of forage and shelter—distribution patterns that have developed over thousands of years.

Are fences being upgraded to be friendly?
As old fences are replaced on public lands, managers are required to use wildlife-friendly fence standards. Unfortunately due to serious livestock trespass and damage problems, some managers, including the Wyoming Game and Fish Department, are effectively blocking wildlife movements on state and public lands with fences that are unfriendly to wildlife.

Another problem is that highways and their right-of-way fences are not compatible with wildlife movement since the Wyoming Department of Transportation allows landowners to choose the style of fence they prefer, and these may not meet the voluntary wildlife-friendly fence standards. However, there are some incentives for change, particularly in areas that have been identified as critical to wildlife migrations.

The Wildlife Heritage Foundation of Wyoming has contributed $70,000 for private land wire fence modification to facilitate wildlife migration near Trappers Point, in the Upper Green River Valley. Trappers Point is the spot where the longest migration corridor in the continental United States—one used by pronghorn moving from Grand Teton National Park down into the Upper Green—pinches down to a passage that is only .75 miles wide.

In 2003, the Trappers Point Working Group was organized to solve some of the pronghorn and mule deer movement problems at the bottleneck. The group is comprised of representatives from the local ranching community, federal and state agencies, private landowners, recreationists and the Wyoming Outdoor Council. In 2004, BLM responded to recommendations from the group and installed a wildlife-friendly fence at Trappers Point.

The Wyoming Department of Transportation has widened the right-of-way between the fences and highway. They have also constructed an underpass, although most wildlife seem not to use it. The Department is now installing flashing lights and an electronic sign to warn motorists of wildlife crossing at Trappers Point.