How does a pronghorn get safely through a barbed-wire fence? That was the question posed by researchers in a study conducted by The Nature Conservancy in Montana and our partners. The answer proved to be a surprise.
Because pronghorn evolved grasslands, where they didn't see anything taller than a sagebrush, they aren't big jumpers. When confronted with fences, they crawl under rather than jump over. But, when the bottom strand of gnarly barbed wire is too low, it can scrape the hide right off the animals exposing them to frostbite and infection.
PHOTO: Hide scraped off back of pronghorn, exposing skin.
So, the team tested three different fence types. Each raised the bottom wire to at least 18 inches above the ground – to allow enough room for pronghorn to crawl under. In one group they replaced the bottom barbed wire with a smooth wire. In the second they clipped the bottom wire to the span above it, raising it higher. The third was the so-called “goat bar” which encases the lower two wires in a plastic pipe – an often-recommended modification. The big surprise was that the highly touted goat bar was a near total failure. Both pronghorn and deer balked at that one. The other two worked well.
PHOTO: Young bucks check out a goat bar
Researchers used remote cameras on the Conservancy’s Matador Ranch and in Alberta, Canada to monitor whether pronghorn were crossing the various fence types. The bottom wires of many fences are too low for pronghorn to crawl under, or may scrape fur from their backs, leaving them susceptible to frostbite and infection. A successful fence would let pronghorn pass through, while keeping cattle inside.
PHOTO: Sliding under a smooth bottom wire
It also turns out that pronghorn are creatures of habit. They tend to return to the same crossing points year after year, and condition their young to do the same. That finding helps us make smart decisions about where to remove or modify fences or to simply leave open a gate.
“Results from this research can be used across the species’ range. Raising bottom fence wires with a clip can be a great first step in enhancing the passage for pronghorn, given how quickly it can be accomplished for a minimal cost,” says Montana’s Grasslands Conservation Director Brian Martin.
PHOTO: Bottom wire clipped up to raise level from the ground
Of course, the best fence for wildlife is no fence at all. So, researchers also removed 20 miles of fencing and raised the bottom wires on another 66 miles, using funding from the National Fish and Wildlife Foundation, which backed the study. Our partners were the Alberta Conservation Association and University of Montana.