Study shows dramatic declines in mule deer, pronghorn antelope herds along Wyoming, Colorado border

Decrease blamed on increase in oil and gas drilling

By Troy Hooper
Real AspenJuly 21, 2011
The industrialization of once wild landscapes is partly to blame for dramatic declines in mule deer and pronghorn antelope in Colorado and Wyoming, according to a new report.

After reviewing population trends, hunter-harvest reports and licenses sales from the two states over the last 30 years, wildlife biologists John Ellenberger and Gene Byrne concluded that oil and gas drilling, wind farms, agricultural practices and other human encroachments are slicing and dicing critical habitat the animals have historically relied upon to survive phenomenons of drought, weather and disease. The result: A slow, inexorable decline in populations of both species.

Humans are “cutting these big legendary Western landscapes into smaller and smaller islands of habitat. Not only is the winter range not as big and leaving mule deer and pronghorn antelope with fewer options but even the summer range is being impacted and, in some cases, the corridors the animals use to move between these ranges are being restricted by industrial uses,” Steve Torbit, the National Wildlife Federation's regional executive director, told the Colorado Independent this week. “Some of those chunks of land are just not useable and the animals' biological response is to either leave or die.”

Young buck in Colorado.
David O. Williams

The study, titled “Population Status and Trends of Big Game along the Colorado/Wyoming State Line,” is the first professional review of broad statistics over such a long period of time. It focused on both sides of the Colorado-Wyoming border in an area roughly bounded by Interstate 80 to the north, the Green River to the west, U.S. Highway 40 to the south and Laramie, Wyo. and Walden, Colo., to the east.

Although the Wyoming Department of Game and Fish and the Colorado Division of Wildlife do share information for big-game management, much of the federal land along the common border is overseen by the U.S. Bureau of Land Management, which is administered by state directors whose mandate is “to focus on issues specific to the state they work in” and that “can lead to decisions that may be detrimental to neighboring states,” National Wildlife Federation representatives assert.

Too often, federal land managers approve development that characterizes itself as good for jobs and good for the economy without acknowledging it is detrimental to the ecosystem, according to the report.

“The BLM must recognize the cumulative, landscape-wide impacts of its decisions and that a lease or permit granted in one area or state can directly result in added stress to migrating game herds in an adjacent state,” Torbit said. “The needs of wildlife over the entire landscape need to be fully factored in before permits for oil, gas, wind farms, agricultural practices or any other human activity are permitted.”

Biologists dismiss claims from some area residents who believe coyotes and other predators are responsible for the decline in mule deer and pronghorn populations. There are fewer predators than before, the biologists point out, and historically deer and antelope herds have recovered from nature's killers.

“What's changed are the intense demands we are placing on Western landscapes,” Torbit said. “It appears that the new predator is the increased development and other human activity that has picked up pace over the past several decades. Mule deer and pronghorn are now experiencing 40-acre spacing of gas drilling pads and thousands of miles of roads and pipelines.”

With oil and gas development expected to surge as new fields in the Niobrara Formation are tapped along with other wide-open tracts in the West, biologists are concerned for the future of the animals.

“Evaluations of impacts to wildlife and wildlife habitat need to be performed at the landscape level, not just localized impacts,” said Ellenberger, the study's co-author. “We are concerned that at some point, the resiliency of these herds to recover will be lost, creating a situation where we can only expect further declines.”

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