Wildlife

Fences hinder migratory wildlife in Western US

Each year, thousands of migratory mule deer and pronghorn antelope journey northwest from their winter homes in the Green River Basin, a grassland valley in western Wyoming, to their summer homes in the mountainous landscape near Grand Teton National Park.

But to reach their destination, these ungulates must successfully navigate the more than 6,000 kilometers (3,728 miles) of fencing that crisscrosses the region. That’s enough distance to span nearly twice the length of the U.S.-Mexico border.

Fences don’t always pose an insurmountable barrier to wildlife, and different species find different ways to get around them. Mule deer are willing to jump over fences that are low enough. Pronghorn antelope, however, are reluctant to jump over fences and instead must seek out areas where they can move underneath.

Each year, mule deer encountered fences an average of 119 times, Xu found. Pronghorn antelope encountered fences at more than twice that rate, about 248 times per year. About 40% of these fence encounters resulted in a change in the animals’ behavior.

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