IN BETWEEN:

The marvel of the Greater Yellowstone Ecosystem’s migrations

The network of migratory wildlife that pulses in and out of the Greater Yellowstone Ecosystem’s core is one of the ecological phenomenon prized not just within the United States, but the entire world. And there’s a unique opportunity to save the whole system.

NE DECADE AGO, GRAND TETON NATIONAL PARK

biologists set out to learn where the mule deer that live in the park in the summer came from and what route they took to the Tetons.

There were some assumptions going into this 2013 effort to dart, capture, and collar dozens of doe deer in places like Jenny Lake, Colter Bay, Flagg Ranch, and Moose. Some of the animals likely came from eastern Idaho, past research had suggested. But other than that, there was little indication of where the Tetons’ summering deer spent their winters. Their paths to get there—i.e., their migration routes—were equally unknown. That fall and winter, when location results started trickling back from the deer’s GPS collars, biologists were struck with awe. Three previously unknown migration paths shot off to the east, tying the Tetons to places like the Absaroka Front and the Wind River Indian Reservation. Other deer trekked south, headed down the Green River Basin toward Rock Springs. The suspected westward travelers materialized too—deer bound for the Teton River corridor and Idaho’s Sand Creek Desert. Yet other park deer completed shorter seasonal journeys within Jackson Hole, headed for places like East Gros Ventre Butte and Cache Creek.

“These results were just simply incredible,” Teton Park wildlife biologist Sarah Dewey told an audience in 2021. “What these deer ended up doing just blew us away. It wasn’t just a single migration corridor. It turned out to be a whole network.”

If there’s anything unsurprising about the miraculous migratory melting pot of mule deer discovered in Grand Teton National Park a decade ago, it’s that they dwell in the Greater Yellowstone Ecosystem. It’s an intact, interconnected roughly 22-million-acre ecological complex that spans three states, 17 counties, and myriad land jurisdictions—and it’s absolutely teeming with migratory wildlife, including bison, moose, elk, mule deer, and pronghorn antelope. Superlatives are appropriate when describing the tens of thousands of ungulates flowing like a two-way river to and from the ecosystem’s high country to lower-elevation deserts and grasslands. “As we are getting a clearer picture of migrations around the world, we’re learning that the Greater Yellowstone is really this unique migratory landscape,” says Matt Kauffman, a University of Wyoming professor who leads the Wyoming Migration Initiative. The special stature of migration in the ecosystem isn’t limited to the ecological phenomenon, he says. “In some ways, what’s more exciting to me is that the opportunities to conserve the migrations of the Greater Yellowstone area are really unparalleled on a global scale.”

Migration policy and conservation are being pioneered in the region and in Wyoming. Jackson Hole’s 400 or so pronghorn pass through the first federally protected migration corridor in the United States, a route through the Gros Ventre and Upper Green River drainages known as the Path of the Pronghorn (see sidebar, page 116). It was designated by the Bridger-Teton National Forest in 2008, though southern reaches on Bureau of Land Management property still haven’t been protected 15 years later due, in part, to political pressure to not impose restrictions on valuable natural gas fields. A decade later the state of Wyoming followed federal land managers’ lead, designating the Red Desert-to-Hoback migration corridor—traveled by some of Dewey’s tracked deer—and two other mule deer migration routes via an executive order signed by Gov. Mark Gordon. “It is one of the first forays into the conservation of wildlife migration corridors,” says Matt Skroch, who directs a migrationfocused program for the Pew Charitable Trusts. “After several years, despite hav- ing some challenges in implementation, it remains one of the most robust actions by a governor in a Western state to conserve wildlife migration.”

There wouldn’t be such a robust effort to protect migrations if they were already gone. In much of the world and the American West, they’ve been wiped off the map. There’s a whole book about the largely human-caused collapse: David Wilcove’s No Way Home: The decline of the world’s great animal migrations What makes the Yellowstone region buck the trend?

One theory is that the ecosystem is a hotspot for migration partly due to another hotspot, this one geologic. A magma chamber pressing up against the earth’s surface has elevated the