Biologists Launch Study of Greater Yellowstone Mule Deer Migrations

Wildlife researchers have launched a landmark study to map mule deer migration corridors over the entire eastern portion of the Greater Yellowstone Ecosystem. It is one of the largest collaring efforts ever conducted in Wyoming, focused on multiple herds and spanning an area from the Wind River valley to the Bighorn Basin.

researchers releasing mule deer

The study is a unique collaboration between the Wyoming Migration Initiative, the Wyoming Game and Fish Department, and The Nature Conservancy. Researchers and managers increasingly recognize the importance of intact migrations for healthy, abundant mule deer herds.

The mapping project will document in detail the migration corridors of several key herds that have never been the focus of the latest tracking technology. All 90 animals captured will be fitted with “real-time” GPS collars that send data back to researchers every three days. That represents a vast improvement over previous GPS studies that required researchers to recover dropped collars to download the data after one to three years.

The study targets deer in five separate herds near Cody, Meeteetse, Dubois, and Lander. A second collaring effort to bolster sample sizes on these same herds will occur in 2017. Individual mule deer will carry the collars for up to two years, gathering movement data from two cycles of spring and fall migration.

The real-time data from these collars allow researchers to do something new for wildlife research in Wyoming: They will share what they learn with the public as collared deer make their migrations through one of the wildest areas of the continental United States.

From late March through mid-summer the collaborators will post maps of these migrations weekly on Facebook and Twitter using the hashtag ‪#‎wyodeer‬.

Matthew Kauffman, Wyoming Migration Initiative director and zoology professor at the University of Wyoming, says the study is timely. It follows on the recent decision by the Wyoming Game and Fish Commission’s to define additional aspects of migration corridors as “vital” habitat.

Study area of GYE mule deer migrations

“In order to plan for these migrations across the many habitats they require, you need to have detailed maps of the critical corridors and stopover areas, and knowledge of where the obstacles are,” Kauffman said. “This study will help Game and Fish, other wildlife researchers and conservation groups pinpoint potential trouble spots and specific conservation opportunities, and that should benefit Wyoming’s struggling mule deer herds.”

Since 1990, mule deer populations in Wyoming have declined 36 percent due to various factors including weather, habitat, competition, predation, and disease.

In response, the Wyoming Game and Fish Department created the Mule Deer Initiative, an effort to stop the decline and work towards growing the herds again.

“The Wyoming Mule Deer Initiative is a long-term endeavor to conserve an iconic species,” said Daryl Lutz, Game and Fish’s wildlife management coordinator for the Lander region. “It is not easy work and our Commission has committed to invest significantly in mule deer. This study is another way for us to advance conservation with many partners.”

The study may also help game wardens focus anti-poaching enforcement surges to specific areas of winter range.

The Nature Conservancy of Wyoming is a key collaborator in the study. For decades the nonprofit has preserved big-game winter range through conservation easements along the eastern Greater Yellowstone Ecosystem.

“This part of the GYE is a critical area for our land conservation, and protecting big game migration corridors has become a priority for TNC Wyoming,” said Holly Copeland, TNC ecologist in Lander. “Since detailed maps of these corridors don’t yet exist, we were keen to partner with WMI and WGFD to do the research that can guide our work to conserve these critical corridors.”

For decades scientists have suspected that mule deer in the region migrate in surprising ways, perhaps ranging from the Tetons to the eastern edge of Greater Yellowstone near Cody. Pioneering biologist Olaus Murie wrote of similar movements in 1929.

Hunters, taxidermists, and timber harvesters in Dubois have also seen clues of local deer spending summer near Jackson Hole or Yellowstone Lake. Tracks left in snow in the Mt. Leidy area hinted at a possible migration east over the Continental Divide to Dubois or the Cody area.

While few details existed on such routes, a recent study conducted by Grand Teton National Park biologist Sarah Dewey indicates such migrations could be very impressive.

Dewey collared deer near Jackson Lake during summer. At least one deer ranged west to the Idaho border, then made its way east to Dubois. Other Teton deer wintered on the South Fork of the Shoshone River, just outside of Cody.

Dubois Game and Fish Warden Brian Baker spotted a collared mule deer doe in the town of Dubois this winter, which he suspects was part of Dewey’s study.

“We know some of the mountain passes that migrating elk are using, and there is no reason to think that deer couldn’t use a lot of these routes,” Baker said.

In Lander, Game and Fish warden Brady Frude and biologist Stan Harter hope the study will show how deer move in the foothills east of the Wind River Range.

A deer collared in the 1980s at Beaver Rim south of Lander migrated around the south end of the Wind River Range to Boulder, Wyoming, Harter said. That’s a distance of about 100 miles over South Pass.

Arthur Middleton, a WMI researcher and study collaborator who recently completed a comprehensive map of elk migrations in Greater Yellowstone, sees the mule deer study as another step toward the long-term goal of mapping all ungulate migrations in Greater Yellowstone. “Ungulates are the lifeblood of this incredible ecosystem,” Middleton said.

Wyoming is home to the longest-known mule deer migration in the lower 48 states, a 150-mile journey that stretches from the Red Desert to the Hoback. The trek ranges from lowland sagebrush steppe in winter to lush mountain ridges in summer.

Mule deer evolved these iconic seasonal migrations to maximize their search for the best forage, a highly effective survival strategy in Wyoming’s harsh climate.

“I think deer are going lots of places that will surprise us when we see their actual movements,” Dubois warden Brian Baker said. “I am really interested to see where these deer go.”

The study is funded in part by the Knobloch Family Foundation, The Nature Conservancy, the Bole and Klingenstein Foundation, Wyoming BLM, Wyoming Governor’s Big Game License Coalition, 10 Country Chapter of Muley Fanatic Foundation, and the EA Ranch of Dubois.

Follow along on Twitter with #wyodeer using @wyokauffman @GregNickersonWY and @WGFD,, or WMI Facebook and WGFD Facebook.