PINEDALE, Wyo. — When the snow cover peels off the Upper Green River Basin, a biannual dance springs to life outside this century-old ranching community. Thousands of pronghorn antelope head north, the females deep into pregnancy, to birthing grounds and summer range at higher elevations.
Last April, in the sagebrush between Jackson and Pinedale, I encountered numerous bands of these tan and white creatures on the way to their summer haunts in the mountains. They grazed peacefully, until they noticed me watching. Then they were off and running at highway speeds.
One of nature’s greatest athletes, Antilocapra americana is the continent’s swiftest animal. Having co-evolved with a long-extinct cheetah-like cat, the pronghorn is capable of sustained speeds of 50 mph.
While every other surviving species of North American ungulate is linked to forebears that crossed the Bering Land Bridge from Asia, the pronghorn is a true native, the sole surviving member of a family that dates back 20 million years.
Prior to white settlement, pronghorn rivaled the great herds of bison that also roamed the Plains; ecologists estimate there were 30 to 60 million of the animals. Wholesale slaughter drove them to near extinction at the turn of the 20th century; then conservation, led by sport hunters, allowed their numbers to rebound to about 1 million in North America.
Today, about half the entire pronghorn population lives in Wyoming, making the animals more plentiful than people in the so-called Cowboy State. But the pronghorn remain vulnerable, because they need open land. They tend to avoid forests and thick brush, and are unwilling to jump fences, though they can duck under barbwire with an effortless downshift.
One band of several hundred pronghorns here has become a cause célèbre among conservationists, because it makes the longest overland migration of any animal in the Lower 48 states. The twice-a-year trek takes the band between winter range south of Pinedale and summer pasture in Grand Teton National Park. The migration, which crosses a 9,000-foot pass in the Gros Ventre Mountains, stretches 160 miles one-way.
But the future doesn’t look bright for this band, or for any of the other 46,000 pronghorn that spend part or all of the year in the Upper Green. The basin — which is also home to 60,000 deer, elk, moose and bighorn sheep, and one of the largest remaining populations of sage grouse — happens to sit on top of one of the nation’s richest natural gas deposits. Under energy-policy directives coming out of the White House, and with headlines screaming about a gas shortage, the southwest corner of Wyoming — already a full-fledged resource colony — is getting even busier, swarming with seismic-exploration thumper trucks, drilling rigs and Texans.
The federal Bureau of Land Management, which is the primary landlord here, has already leased about a million acres for possible drilling — 86 percent of the Pinedale Resource Area, plus the rights under some private and state land. The players include multinationals such as ExxonMobil, Enron Oil and Gas, EnCana USA, BP America, and billionaire investor Warren Buffet, who owns a giant pipeline that connects to power plants and other energy-hungry customers in Southern California.
The gas boom promises to test industry’s professed commitment to tread lightly on the land. It’s also shaping up to be an epic struggle between two core Western values: conservation of wildlife and resource extraction.
An arid, high-elevation sagebrush plain with only a few thousand human residents, the Upper Green River Basin is hemmed by spectacular mountains including the Wind River, Gros Ventre and Wyoming ranges. To get back and forth from the mountains, the pronghorns that winter in the basin — and their distant cousins, mule deer — follow ancient migration corridors that narrow in places biologists call “bottlenecks.”
The most famous bottleneck is a few miles west of Pinedale, where the terrain undulates to a high point between the Green and New Fork rivers. Several thousand pronghorn and deer pass through Trappers Point, among them the far-ranging Teton Park band. The topography funnels them through a mile-wide slot between the rivers — a bottleneck that’s been effectively narrowed to just a half-mile wide by a scatter of houses, dirt roads and U.S. Highway 191.
I visited Trappers Point in April at the tail end of the migration with Meredith Taylor, a veteran Wyoming Outdoor Council conservationist and Dubois, Wyo., outfitter. “This is the neck of the hourglass. You see those pronghorn over there?” she said, gesturing toward a group across the highway. “That’s where it’s starting to widen out.”
The place has been a busy wildlife crossing for thousands of years. When Highway 191 was widened in the early 1990s, crews uncovered a 6,000-year-old kill site. From the bones and spear points, archaeologists determined that ancient hunters took advantage of this bottleneck to lie in wait for migrating antelope. Fetal bones indicate the pronghorn were killed at a late stage of pregnancy, offering proof they were passing through at about the same time of the spring as they do today, says Dave Vlcek, a BLM archaeologist.