Working Toward a Better Migration for Yellowstone's Pronghorn
Getting landowners to remove or alter fencing is key to restoring pronghorn routes and improving their overgrazed, overdeveloped winter habitat.By Melynda Coble Harrison, 11-03-10
Pronghorn and fawn in the Lamar Valley of Yellowstone National Park. | |
The doe is agitated and tries to break free of the buck, but he chases her and herds her back.
From this spot, the group can look past the pronghorn and into the Gardiner Basin. What used to be prime winter habitat there is now overgrazed and developed. Before ranches sprung up all over southwest Montana, the park's pronghorn migrated beyond the park boundaries to Paradise Valley—all the way to Livingston. But unlike deer, elk or moose, pronghorn can't forage through deep snow, so they moved into a winter range where strong winds keep the ground relatively snow-free. Come spring they run back into Yellowstone.
Joe Josephson, wildlife fellow for the National Parks Conservation Association's Yellowstone Field Office, talks to the group about pronghorn courting dynamics and explains the action taking place below them. His audience listens carefully, all the while scanning the hillsides for more of the ungulates. Josephson is working with about a dozen landowners in a two-mile stretch critical to pronghorn migration. There are three natural bottlenecks, so NPCA is trying to remove or alter fences to open up the areas on either end of these areas. During one of Josephson's work parties, his group took down a couple miles of fence in the Gallatin National Forest. "You don't have to remove the fence for pronghorn," he said. "It just has to be passable to wildlife, while still working for the landowner." As Scott Bergen, a researcher with the Wildlife Conservation Society (WCS), also at work on this issue: "Pronghorn don't like places where they can't see far or run fast."
European explorers called them "antelope" or "goats" because of their resemblance to familiar animals, but pronghorn are unique to North America and have no close relatives anywhere in the world. They evolved in the Pleistocene along with dire wolves and saber-toothed cats in places where their incredible speed helped them avoid being eaten. Regardless of how fast pronghorn are, when faced with a fence, they either crawl under (if there is room and they aren't pressured) or they stop. These days, Yellowstone's pronghorn are largely limited to the park and Gardiner Basin, where they compete with development and other animals, turning it into a tough, degraded habitat.
Around 1995, some pronghorn desperate for fresh forage found their way through Yankee Jim Canyon onto ranches along the Old Yellowstone Trail north of Tom Miner Basin. Once there, many stayed year-round, effectively creating another population.
Watching for pronghorn atop Mount Everts. Photo by Melynda Coble Harrison.
Similar work is happening with landowners and public entities on a recently discovered route that includes southeast Idaho and western Wyoming. The herd summers at the base of the Pioneers Mountains and migrates to the Continental Divide's Beaverhead Mountains, passing through Craters of the Moon National Monument – a roundtrip of more than 160 miles. The route crosses federal, state and private land and narrows in one stretch to a bottleneck narrower than two football fields. There, animals are restricted by mountains, fences, Routes 20 and 26 and lava fields in Craters of the Moon. Its discovery is part of an ongoing study to track the herd's migration. The 1,200- to 1,500-member herd that winters together, breaks apart when it's time to head to summer ranges and no one is sure exactly where they all go or how they get there. But according to WCS' Bergen, the winter range is already tough, with just enough sagebrush, water and space for the thousands of deer, moose, elk and pronghorn that winter there. Adding habitat fragmentation and obstacles make it extremely challenging for pronghorn.
WCS is working with Craters of the Moon National Monument and private ranches to take out or rehabilitate fences. Some ranches have long been supportive, including Lava Lake Land and Livestock, which established an institute to study habitat and migration on its grazing lands and is part of the "Freedom to Roam" campaign started by Patagonia. The Idaho pronghorn project is contributing data to a Western Governors Association (WGA) pilot project dealing with wildlife connectivity and core habitat issues. There are nine projects all together, including "the Path of the Pronghorn"—the seminal study that garnered federal and WGA support and action. Established on a route tracked by WCS, scientists used GPS collars to document pronghorn traveling from Grand Teton National Park to the Green River Valley (150 miles round trip) or even farther—up to 400 miles roundtrip for the animals that make it all the way to Rock Springs. It's the longest terrestrial migration in the lower 48 states—tagged "the Path of the Pronghorn." "In a country with over 3 million people, that's a pretty substantive distance," said Joel Berger, a WCS scientist who's on the faculty of the University of Montana's wildlife biology program. In 2008, the U.S. Forest Service adopted an amendment that aims to safeguard significant parts of the corridor. The 10-year plan doesn't allow any building without an environmental assessment and public hearings, Berger said. No new fencing is allowed and established fencing must be modified to be wildlife-friendly. "We wanted everyone to feel good about (the Path of the Pronghorn) and a wide group of people were supportive," Berger said. "There were no takings, cattle can still graze and people like pronghorn. They're not eating sheep, they're not eating cattle and they're not moving disease around."
Up on Mt. Everts, Josephson's pronghorn-watching group finishes up a day of following a small part of the pronghorn migration route. They scramble and slide down a steep hill, avoiding cactus, rocks and rattlesnakes, wishing they had the dexterity and endurance of pronghorn. They end their hike in the Gardiner Basin—winter range for Yellowstone's pronghorn.
What's clear, even to this group of casual observers, is that this part of the herd is isolated from other pronghorn in the area and has minimal forage available. These conditions put them at high risk for disease, predation and inbreeding.
"Without action, we risk losing one of the West's most iconic species in Yellowstone National Park," Josephson said.
Great article. So true, so well written. People don't appreciate how our fences and development have altered precious habitat for so many species. Pronghorn are beautiful animals with spectacular instincts and need their migratory routes open. Thank you for writing this. I will be sharing it!
ReplyDeleteThanks for posting my piece. People like pronghorn, so they are good ambassadors for getting folks to mitigate fences etc.
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