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Wednesday, May 10, 2017

How do pronghorn cross the fence?


Alberta Conservation Association - 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 (global affiliate of TNC Canada), the University of Montana and Alberta Conservation Association. The answer proved to be a surprise.

The team tested three different fence types. Each raised the bottom wire to at least 18 inches above the ground - since pronghorn crawl under rather than jumping over fences. 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. Both the other two modifications worked well.



"Our team wanted to critically evaluate three commonly recommended fence modifications to allow daily and seasonal movements of pronghorn. We...found that previously recommended goat-bars did not improve movements and in many cases, deterred movement... On top of that, no cattle crossed under smooth wire or clips during the entire project, which makes these modifications useful for working ranches," says Andrew Jakes, University of Montana post-doctoral researcher.

Researchers used remote cameras on the Conservancy's Matador Ranch and in Alberta, Canada to monitor whether pronghorn were crossing the various fence types.

"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 the Conservancy's Grasslands Conservation Director Brian Martin.

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 ranchers make smart decisions about where to remove or modify fences or to simply leave open a gate.

Of course, the best fence for wildlife is no fence at all. "So, we partnered with the Alberta Fish and Game Association and their volunteer army and removed 20 miles of fencing and raised and replaced the bottom wires on another 66 miles," says Paul Jones, senior biologist with Alberta Conservation Association. In addition, over the last few years, the Conservancy has removed or modified another 50 miles of fence on our Matador Ranch and with our grassbank partners.

Funding for the study was provided by the National Fish and Wildlife Foundation.



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