Pronghorn numbers drop; researchers look for answers

Snow fell heavily in the winter of 1994, coating Glendo Reservoir and drifting over fences.

A small herd of pronghorns living east of the reservoir migrated west, looking for better forage and thinner snow. They walked on top of the frozen lake, wandered over covered fences and crossed Interstate 25, said Mark Zornes, Green River wildlife coordinator for the Wyoming Game and Fish Department, whoat the time worked in Wheatland.

Then the snow melted, and they couldnt get home. Theyve been stuck there ever since, he said. That is the problem fences cause pronghorn. But if the fences werent there, wed have killed them all on the interstate. Youre darned if you do, darned if you dont.

Antelopes didnt evolve to jump like deer or elk, Zornes said. They will walk up and down a fence until they die.

Barriers such as fences continue slicing through antelope ranges, forcing them to live in smaller and smaller areas. And it may be starting to take its toll.

While seemingly abundant across Wyomings plains, pronghorns no longer outnumber people in the Cowboy State. Researchers know that hard winters and drought have played a role in lowering their numbers, but they also want to know to what degree the species' inability to migrate has contributed to the decline.

Pronghorns, like many species in the West, were hunted to near extinction at the turn of the 20th century. Conservation efforts brought them back, and by the mid-2000s, their numbers held strong around 560,000 animals -- more than Wyomings human population.

Then hit the winter of 2007-08, a prolonged drought and another bad winter in 2010-11.

Their numbers dropped to just over 400,000 in 2012 and about 367,000 in 2013, reported Grant Frost, a wildlife biologist for the Biological Services.

Pronghorns have endured hard winters and drought in the past. The problem is that they arent rebounding as they normally would, said Tony Mong, a wildlife biologist for the Game and Fish Department.

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Pronghorn numbers drop; researchers look for answers