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Journey's End?
Development threatens to sever the pronghorn's ancient migratory route
They don't linger long—these rows of pronghorn with oblong faces and black nose splotches poking out from an endless sea of sage. Surprised by the pickup truck lurching across the bumpy terrain toward them in the midday sun, the animals launch into an all-out sprint, their characteristic white rumps quickly obscured by dust clouds. They run so far so fast that within seconds they're out of sight, even on this flat landscape—flat, that is, except for the mountain range rising in the distance and the natural-gas well that mars the view.
When the dirt track across federal Bureau of Land Management property nearly dumps biologist Leigh Work's cherry red truck straight into a three-foot sinkhole, we have literally come to the end of the road. “This is where life gets interesting,” she says, grabbing her tracking equipment and taking off down a path so densely trodden by pronghorn that the hoof prints look like tire treads.
This is the winter range for several thousand pronghorn in western Wyoming's Upper Green River Basin, including a herd of 200 to 400 that migrate here from their summer stomping grounds in Grand Teton National Park about 150 miles north. For at least 6,000 years, these pronghorn—three-and-a-half-foot tall, antelope-like mammals—have traveled with the seasons. In winter, flanked by the Wind River range to the east and the Wyoming range to the west, they inhabit the sage-swept lowlands, where less snow makes foraging easier. In spring, they head north to the uplands, where lush meadows provide sustenance until the aspen leaves turn yellow and drop, and crimson willow stalks again sweep the riverbanks.
Recognized as the longest migration by land mammals in the lower 48 states, this 270-mile roundtrip trek made in groups of three to 20 at a time in about a three-day period is now in jeopardy from private land subdivisions—complete with fences and guard dogs, while an energy development boom threatens the pronghorn's traditional winter habitat.
Defending Pronghorn
Defenders has long worked as part of the Upper Green River Valley Coalition to maintain pronghorn and other species in Wyoming's Upper Green River Valley by limiting the negative effects of rampant energy development on wildlife and human communities. At the southern portion of the greater Yellowstone ecosystem, the valley hosts more than 100,000 big game animals, including the largest mule deer herd, and is home to the longest big-game migration corridor in the lower 48 states.
Defenders and the coalition have worked to draw international attention to this irreplaceable wildlife resource and has petitioned the Bureau of Land Management to designate the most important portions as “areas of critical environmental concern” to protect imperiled migration corridors and winter range essential for pronghorns, mule deer, elk and bighorn sheep.
Defenders is also leading efforts to strengthen wildlife management standards on America's public lands—in the face of the Bush administration's relentless campaign to remove crucial wildlife safeguards in the National Forest Management Act—and to ensure the long-term health and vitality of wildlife populations that range across the jurisdictions of many federal agencies.
For more information on Defenders' work on public lands, and what you can do to help, please visit www.defenders.org/ YourLandsYourWildlife.
In the last decade, encouraged by rising energy prices and a pro-development Bush administration, nearly 3,500 wells have been sunk here, accompanied by a network of roads, powerlines and pipelines to service them. And rather than enforcing seasonal restrictions to prevent drilling during the harshest winter weather (to limit detrimental effects on wildlife) as happened in the past, the administration is granting exceptions to energy extractors as it also moves to allow more than six times the number of wells currently permitted. More than 75 percent of the 1.2 million acres of federal land here is already under lease for oil or gas extraction.
“It's an environmental catastrophe in the making, and those living outside of the Rockies are largely unaware of it,” says Mike Leahy, Defenders of Wildlife's regional director in the Rockies. “The Bush administration has turned this vital habitat into a national sacrifice zone.”
This is especially worrisome in areas where natural land features already cause bottlenecks that constrict paths to a width of a couple of hundred yards. With one historic migration route still available to the only long distance pronghorn migrators left here, Work's research, and that of her fellow Wildlife Conservation Society biologists, Kim and Joel Berger and Jon Beckmann, is crucial to preserving this ecological phenomenon—and the presence of pronghorn in Grand Teton National Park.
The worry is not that these 100-pound animals will disappear—some 800,000 pronghorn still lay claim to North America's grasslands, scrublands and desert habitats, stretching from Canada down into Mexico—but that further development will stop the animals from migrating. “It's not a matter of losing the pronghorn—they will still exist,” says Work, “just not in Grand Teton National Park. Once you sever a migration corridor it's nearly impossible to repair.” Three years into a five-year study, the team is trying to determine how adept these pronghorn are at navigating the fields and what can be done to ensure this species' age-old epic migration doesn't slide into oblivion—like that of the bison's.
“Hindsight is 20/20,” Beckmann tells me the night before, while the team discusses their action plan. “We want to address the problems before the pronghorn shoot off a cliff, before they get into total freefall.” One of the researchers' concerns is that they might not figure out all the areas needed by the pronghorn until it's too late. “We're having mild winters right now, and pronghorn numbers seem to be improving,” adds Kim Berger. “But what about that one-in-10 bad winter? The pronghorn might need a particular place to find food. If it's been developed by then, it's a problem.”
This is the reason why Work is out searching for dropped radio collars this morning. Last December, the team net-captured and radio-collared 50 pronghorn. The collars track the animals by satellite and are timed to pop off the pronghorns' necks the last week of October—wherever the animals happen to be standing or stampeding at the time. “It could be a pasture next to a road or in a roadless area in the middle of the national forest,” says Work. “Then depending on snow, we either hike or get out the cross-country skis.” It takes five to 10 days to find all the collars. The data from the collar will tell the researchers the exact route taken by each of these pronghorn during their migration. Yesterday Beckmann flew over their winter grounds to pin down the coordinates of dropped collars and get Work close. Her goal is to find five today before the sun goes down and the programmed collars turn off for the night to save on batteries.
With her GPS (global positioning system) as her guide, Work makes an abrupt left-hand turn and tramps briskly into the sage, dodging the narrowly spaced, foot-high brush as best she can. She moves in a zigzag for about 20 minutes before pulling out her telemetry antenna and starting to twirl, listening for the direction of the strongest beep. Then she's off again. When the beep becomes strong in all directions, all that's left to do is walk slowly in circles and look for a piece of brown leather. It takes about 15 more minutes to find this one. On the way back to the truck an immense funnel of smoke rises up from a distant natural gas well and spreads flat across the horizon.
We're traveling a section of the 200,000-acre Pinedale Anticline (six miles wide and 35 miles long), as yet only 3 percent developed. The adjacent 30,000-acre Jonah Field is the largest natural gas field in production in the country, with thousands of wells on public lands that the Bureau of Land Management leases to energy developers. During drilling, each well pad is like a small town, with generators, engines and processing stations all causing a round-the-clock ruckus.
Besides having to adapt to these disturbances, pronghorn face an additional threat: mass collisions with vehicles that travel the service roads between well pads. As the Western Hemisphere's fastest land mammal at speeds of up to 60 mph, pronghorn once had a pace with a purpose—to outrun long-extinct North American cheetah-like cats—and their herd mentality, which enables them to turn on a dime, kept them safer in a crowd. “When we're flying above them, we can really see how they synchronize their steps,” says Work. “They can look like schools of fish.” But today quick, uniform movement can mean multiple collisions when members of the herd are unable to stop or to separate fast enough to save themselves. Last year, for example, 21 pronghorn died near a station on the edge of the Jonah gas field after running en mass into a service truck traveling 35 mph down a dirt road on a clear afternoon.
Another problem the pronghorn face is barbed-wire fencing, which Work repeatedly points out on our drive to other collar locations. Pronghorn don't like to jump fences and, when possible, will crawl under them—if they don't accidentally plough into them first. But the ground-level, square-pattern fencing favored by the sheep industry is a real problem. “If they encounter a fence they can't get under, the whole group may walk the length of the fence forever, looking for an opening,” says Work. Frustrated, they might eventually attempt to jump it—but too often one will snag and get hung up by a leg. Unable to get loose, it will die draped over the barbs. “There is some good news though,” says Kim Berger when the team regroups about an hour after sundown—and Work has five collars in hand. “Some property owners have been adapting their fences to make them more wildlife friendly.”
Looking for a more permanent solution that would help the pronghorn get to and from their critical winter range, a few years ago Joel Berger began calling for a new type of refuge—the nation's first national migration corridor. Ninety miles long and a mile wide, it would protect those animals that must hoof it for tens of miles—including mule deer and elk. Given that 92 percent of the corridor would run through federal lands, the idea is tenable. “Wyoming has a long tradition of wildlife conservation,” says Kim Berger. “It has the first national park, the first national forest and the first national monument. Now it could have the first national migration corridor.”
Barring that, the researchers worry the Pinedale Anticline will be fully developed before the gas companies can make any changes based on this study's recommendations. “But given the fact that the entire Rocky Mountain region is going to be developed,” says Work, “the hope is that if we can't help matters here, we can take the lessons learned and apply them to other public lands facing the same issues.” Part of the challenge is helping people to see that sagebrush habitat is worth protecting. “People typically see it as wasteland,” adds Kim. “The first thing they often think of is 'how can we get rid of it and make it more productive for us.' But sagebrush doesn't occur anyplace else in the world and a lot of animals besides the pronghorn depend upon it like pygmy rabbits, kit foxes, swift foxes, sage sparrows and sage grouse.”
The next day I make the pronghorn's recent migration in reverse, back to the Tetons, and along a windy, dipping highway. Beckmann tipped me off to a hayfield that the pronghorn use as a staging ground before they begin their fall migration. Last week he watched hundreds gathering here—but it's late in the season. Most have already moved on. I pull off the road and sit, at first seeing nothing. Then the tiny specks in the distance become more obvious. With the help of binoculars, I count 46 white rumps. Heads down, backs to the road, the last of the Tetons' pronghorns are busy filling their stomachs in preparation for their age-old journey.
