How Bad are Fences for Wildlife?

Mule deer trapped in fence

Remains of Mule deer trapped in fence.

I’ve seen it dozens of times before and you probably have too. The partial mummified carcass or skeleton of a deer, elk or antelope hanging in a wire fence. But now here is another one and it’s almost in my back yard. This was one of last year’s fawns that came through our neighborhood last Winter.

We discovered it during the first “dry” walk around the property in late March. We made one “post-holing” trudge and few snowshoe treks back during the Winter, but didn’t see the carcass then. It’s possible we missed it, but I’m thinking this little guy survived his first Winter just to die an agonizing death hanging on a forgotten, unneeded fence.

This fence is on a small piece of remaining Winter range (a quarter section) at the edge of town that has only survived because of the “economic downturn”. Construction had already begun on roads, water and sewer for a new housing development. Then we noticed all the heavy equipment had been removed and the remaining sewer pipes and even the pile of crushed rock had been loaded up and hauled away. Word is, the bank now owns the property.

Since the area is not posted, it offers a place to take a quick walk off the pavement when we don’t have time to get out of town and take a real hike. It’s also still provide some winter habitat for deer, elk and other wildlife. It’s also good for the meadowlarks and the other migrant shrub-steppe birds that still breed here.

But is it really good for the deer population if a neglected fence on 160 acres of land kills a single yearling buck? I’m starting to believe the problem may be bigger than we think.

Study of Wildlife Mortality and Fences

I did some research and found a recent study (Harrington & Conover, 2006) published in the Wildlife Society Bulletin (Volume 34, Issue 5, pages 1295–1305, December 2006) of antelope, mule deer and elk mortality along an 600 miles of road (1,200 miles of fence) in Utah and Colorado. They found 0.25 mortalities per year per km of fence (0.11 antelope; 0.08 mule deer and 0.06 elk) , or one dead antelope every year per 5.6 miles of fence; one dead mule deer every year per 7.8 miles of fence and a dead elk every year for every 10.3 miles of fence.

Obviously every section of fence is not equally good or bad and wildlife will tend to funnel to some sections of fencing more than others.  This study also looked at fences along roads, which will cause wildlife to be spooked by vehicles and to behave differently than they would at fences in the middle of sage flats or forest stands, but one dead antelope, mule deer or elk every 2.5 miles of fence adds up.

The Harrington & Conover study also concluded that fawns and calves were eight times more likely to die in a fence than adults, and that mortality peaked in August about the time that fawns are weaned. In addition to animals found dead and tangled in a fence, they also found a dead ungulate lying next to a fence every 1.2 miles (every year), of which 90% were fawns that are presumed to have separated from their mothers when they were unable to cross the fence.

If the Harrington & Conover study found a dead animal tangled every 2.5 miles of fence every year and a dead animal next to a fence every 1.2 miles every year then over the two year study, they found over 1,900 dead animals in or next to fences in one study.

How Many Miles of Fence?

This is not an easy question to answer and I doubt anyone knows the answer. After much research, I found that the BLM manages for grazing on 157 million acres in 16 western states on 21,000 allotments (data from BLM website) and the U.S. Forest (USFS) manages 193 million acres on 155 National Forests and 20 National Grasslands of which 96 million acres are considered rangeland. I know for a fact that forested acres are also fenced. If the BLM or USFS know the answer, they don’t make it easy to find. I doubt anyone even knows how many miles of fence exist on State or private lands.

The average BLM allotment is 7,476 acres. If the USFS allotments are about the same size, that would total 33,841 total allotments for both BLM and USFS.  If each allotment was fenced with no cross fencing and each allotment was square, each allotment would have 13.67 miles of fence. Since many allotments would share common fences, if we assume that each allotment shares fencing on three sides with other allotments, at a minimum, there would be over 115,000 miles of fence.

If we assume the data from the Harrington & Conover study can be applied to our crude estimate of the amount of fences on BLM and USFS lands, then there could be over 92,500 animals killed annually (in 16 Western states) due to fences.

The Most Lethal Fence for Ungulates

The most lethal type of fence was a woven-wire fence topped with single barb wire strand. This combination trapped more animals than 4 strand barbed wire or woven-wire with topped with two barb wire strands. The biggest danger is animals getting their back legs trapped between the top two wires, so any fence is dangerous if the top wires are loose.

Fence Recommendations for Wildlife

The Harrington & Conover study found that 70% of ungulate mortalities were on fences that were more than 40 inches high.

  •  Highly visible to wildlife and birds – bright colors, flagging, pvc, reflective etc
  • Allow animals to jump over or crawl under
  • Allow access to important habitats and travel corridors
  • 42 inch maximum height of top rail or wire
  • 12 inch minimum between top two wires
  • 16 inch minimum height of bottom rail or wire
  • Smooth top wire or rounded rail, smooth bottom wire
  • Keep in mind that fencing on inclines are harder to jump

Raptor, Waterfowl and Grouse Fence Mortality

Fences don’t kill just ungulates that try to jump over them. The problem extends to birds that fly into them as well.

I know an avid sage grouse hunter (and falconer) who has been saying for years how many sage grouse he has found dead because of fences. He has spent countless hours on his own time putting vertical wooden slats in fences and wiring beer cans to fences to make them more visible to sage grouse, raptors and other wildlife.

So for all you guys out there that have ride around on BLM lands and chuck your beer cans out the window, do something good for sage grouse and wire your cans to a fence instead.

In a study in Wyoming (Tom Christiansen Wyoming Game & Fish),  4.7 miles of fence were checked for mortality between April 2005 and November 2007. The study area was surveyed 9 times and a total of 170 dead birds and 2 dead pronghorn antelope were found. 146 (86%) of the dead birds were sage grouse. (FYI – The U.S. Fish and Wildlife Service is currently in the process of evaluating whether the Greater Sage Grouse should be listed under the Endangered Species Act).

Then, reflective markers were placed on fences to test if they could reduce mortality. Mortality was reduced by by 61% by using various reflectors. Some markers were nearly 100% effective, but were cost prohibitive. I don’t think they tested beer cans or wooden slats.

Another study in Oklahoma claimed that 40% of all Prairie Chicken deaths were due to fence collisions.

FYI, Since 2005, BLM has built 3,150 miles of fence in sage grouse and prairie chicken habitat (reference here).

Federal Budget Issues Prevent Repairs to Fences

One of the main problem with fences seems to be cause when the top strands become loose. They might get lower where it would be easier for animals to jump, but when they get loose, animals are more easily trapped.

The problem on federal land is not likely to get any better according to the USFS 2011 Budget. In the 2011 budget, $298 million have been deferred for critical fence maintenance. If I understand that correctly, that includes money that is needed to repair fences, but due to shortfalls is not available, so fences will get worse.

We should make all those fat DOJ bastards that were eating $16 muffins and drinking $12 coffee while doing absolutely nothing at useless meetings go fix the fences. I have something better in mind for the Federal employees and the Solyndra executives that lost $500,000,000.

Wildlife Safe Fencing Guidelines by State

Elk Calves and New Fence

One June morning just before sunrise, we were driving up an access road across private land to our work site on U.S. Forest Service land. It was just light enough that we could see elk  in the pasture next to the creek. When they saw our vehicle, the herd bolted and ran for high ground. They were angling to cut in front of us, so I slowed down and watched them as they jumped the fence and took off up the hill through the trees. Then we noticed 10-12 calves that were slamming themselves into the barbed wire trying to follow their mothers. I know I have been fortunate to live a fairly sheltered life, but this was one of the most disturbing scenes I have every witnessed.

This was not a normal 3 or 4 strand barbed wire fence, but a brand new, five strand fence with two stiffeners per section and the elk calves were not able to get through the wire. We just sat there starring at their predicament as they repeatedly ran into the fence and bounced off. We watched for several seconds, helpless to do anything, before I floored the truck and moved away, just to remove our presence out of the equation.

When we returned to the spot after work, we could see there was a lot of hair and flesh left on the fence where the calves had tried to cross. There was also a fair amount of hair on the top strand where the adults had jumped, proving that even some of the adults were not jumping the fence cleanly. I didn’t measure the fence, but it seems to be taller than most fences.  It was probably closer to 50 inches tall and and animals crossing from the pasture to the road were also jumping uphill.

As I said, the fence was a new fence.  There had been a fire in the area a few years before and as part of the habitat rehabilitation work, the Forest Service had regraded the road and I assumed they (U.S. Forest Service) had also replaced the fence. By the look of the ranch house, the trucks and the old fences, the ranch didn’t look too prosperous, and I couldn’t imagine that the ranch owner would have spent the money to build that fence on his own.

Who would deliberately build a tall, five-wire fence (with stiffeners or stays) where elk and deer need to cross? Certainly not the U.S. Forest Service, since there are Federal guidelines for fences on Federal land (according to BLM website); All federal fences can not be higher than 42 inches above the ground and the bottom rail or wire must be smooth and allow space for small animals to pass safely under the fence. But this was not on public land. I need to look more into this.

Antelope and Fence

Anyone that has seen antelope run, know why they are the fasted ungulate in the world. One day we were driving along a dirt road that borders U.S. Air Force land and noticed an antelope running down the road in front of us. Antelope are used to seeing cars in this area and usually just move a little way off the road when cars go by, so I don’t know what exactly spooked this one.

I was already driving slower than he was running, so I wasn’t too worried about pushing him. He veered off to one side of the road as if he were going to cross the fence onto Air Force land. I knew the Air Force had replaced the bottom strand of barbed wire with smooth wire to make it easier for the antelope to cross. I was curious to see how this antelope was going to cross the fence while running as fast as he was. They usually drop to their knees and crawled under the fence, but this guy was still moving pretty fast, so I thought he might jump the fence.

The antelope slowed down a little, but instead of jumping the fence, he dove between the top two strands still running at least 20 mph. There was an explosion of dust and fur as he went through the fence and then raced off into the distance. I still cringe thinking about hitting the fence that hard. I guess that guy knows now why luxury car manufacturers have to use European leather.

What Can We Do about Fences That are Dangerous for Wildlife?

I have started carrying wire cutters and gloves with me when I’m hiking around and scouting. I’m not in the habit of cutting fences that don’t belong to me, but sometimes it’s obvious that a fence has been totally forgotten and is posing a danger to wildlife. I also cut and roll up loose wire and sometimes I tighten loose wires. Check to see if your local Rocky Mountain Elk and the Mule Deer Foundations participate in fence removal and other clean-up type projects.

If you own a fence, check it to make sure your animals and the wildlife are safe. Also check out the links above about Wildlife Safe Fencing Guidelines. Private lands are crucial for maintaining wildlife populations, so fixing or modifying fences on private lands may be even more important than on public land. Chances are as a land owner, you know where 95% of the animals cross your fences. A few changes or fixes at a few places may make a big difference to the wildlife in your area.

Why Bother Fixing Dangerous Fences?

Aren’t we supposed to leave a place better than we found it? Because it is the right thing to do.

Years ago, when I was still in school, some friends of mine used to ask me “Why don’t the State do something so we have more raccoons to hunt?” My question to them was “What have you done, so you have more raccoons to hunt?”

If nothing else, if I fix a few bad fences here and there, maybe I keep a deer or two from needlessly dying a slow death. Maybe someone (hopefully me) will even have an extra mule deer to hunt.

Throughout the West, mule deer and antelope populations are declining. There are many reasons for this, but bad fences should not be one of them.

Next time you’re heading out, throw a pair of wire cutters in your pack.

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