In American West, Big Game Need Unbroken Migration Routes

Development threatens wildlife corridors, but solutions are emerging

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In American West, Big Game Need Unbroken Migration Routes
Pronghorn have adapted to thrive in a sagebrush ecosystem.
Emilene Ostlind

Big-game animals in the American West need more than room to move: They need contiguous corridors to travel to and from their seasonal feeding and breeding grounds. To learn more about those needs and what’s being done to meet them, The Pew Charitable Trusts spoke with Emilene Ostlind, editor and communications coordinator for the Ruckelshaus Institute of Environment and Natural Resources at the University of Wyoming. She’s also editor of the recently released Wild Migrations, Atlas of Wyoming’s Ungulates, a project of the Wyoming Migration Initiative.

This interview has been edited for clarity and length.

Q: How is wildlife migration redefining how people consider the ecosystem and species conservation?

A: Instead of thinking of land protections—say, a forest—as enough to sustain an ecosystem, we now understand that migratory ungulates use that ecosystem for only part of the year and are really linking what seemed like different, distinct, unconnected areas—the lower elevations’ sagebrush steppe habitats, and high-elevation forest.

And, through migration, they’re moving nutrients back and forth, affecting the plant systems, perhaps providing their own bodies as sustenance for predators in different areas at different times of year, and affecting the forage in these different habitats. 

When we think about conservation for our ungulate herds, we have to consider that whole picture. You can’t have robust elk populations and beautiful herds of mule deer in the mountains unless they are also accessing and making the most of their winter habitat down in the sagebrush steppes that other half of the year.

Q: What are the implications of wildlife migration for humans?

A: In the Rocky Mountain West and all over the world, there is a lot of value to having large, robust wildlife populations on our landscape. That value could be economic, such as for hunting, wildlife watching, and tourism, or ecological—having robust, intact ecosystems with all the species that belong in the landscape interacting.

Q: You spent four seasons walking one of the longest migration movements in the U.S., 100 miles, from Grand Teton to the Green River Valley in Western Wyoming. What was a highlight of that?

Emilene Ostlind

A: In the springtime, I timed my hike just right so that I reached the high mountain pass of the migration corridor about a day before the pronghorn arrived. I set up a little camp and kind of hunkered in, and in the afternoon, about 150 pronghorn antelope came punching their way through the snow up toward the high pass.

It was amazing to watch them move, almost like they had a drill sergeant shouting instructions, except they were totally silent. But they moved very calmly. They were super organized and deliberate. They all seemed to know the goal and be in communication with each other. At one point, they laid down for a rest. A few of them stayed either standing or holding their heads up to keep watching their surroundings while others just chewed their cud or dozed. And then they got up and started moving single file, taking turns leading the way through the snow.

It was incredible to watch that whole community working in synchrony toward a common goal of reaching this desirable summer range on the other side of the mountains.

Q: Did you see anything that surprised you?

A: Yes, watching the pronghorn cross rivers. There are about five river crossings that they make in this migration corridor. And they have really skinny legs and tiny hooves. You wouldn’t think they could do anything in water, but they were cordoned into these rivers that were swollen with spring runoff, and they kick their legs, and make it across pretty turbulent waterways.

Their hair is hollow and makes them buoyant, so it serves as a life jacket on those river crossings. It’s still dangerous and not all of them make it. But seeing the rest reach that summer range and knowing it’s a perfect habitat for rearing their young—that was pretty neat to experience.

Q: Has the science of studying wildlife migration advanced in recent years?

A: The science of studying land animal migrations, especially these hoofed mammals in the mountains, has taken huge leaps in the past five years. There’s been almost this renaissance of using GPS collars to study migrations. Researchers affix collars to the animals’ necks and program them to record locations several times a day over a couple of years. This tracking has opened up new understanding about the migrations and is helping us answer questions about the areas the animals use, the distances they cover, the time of the year they migrate, the environmental conditions that align with their migration, and the way they respond to obstacles on the landscape.

Q: How does that translate to opportunities for policymakers to affect the course or the success of these migrations?

A: We have an opportunity to use the data of wildlife migration to inform policy decisions about what we do on our landscapes. We could, through data analysis of the GPS collar waypoints, determine the key places for various populations in their migration, and make decisions about where to place infrastructure or other disturbances to either impede or enable the migrations to continue.

Q: What would you say are the biggest threats or challenges that migrating animals face?

A: Herds of elk, deer, bison, pronghorn, and moose need intact landscapes they can move through to get to and from their summer and winter ranges. And that means they can’t have development or highways or fences that cut those migration corridors in half. So, the biggest threat, I would say, to migrating ungulates in the West is infrastructure or development that blocks off migration corridors.

Q: What can be done to help these migrating animals?

A: Now that we know so much about how and where animals migrate in the West, we have an opportunity to put policies in place to direct future development on the landscape away from the migration corridors. In some cases, it’s just a matter of avoiding a place where animals are known to congregate or fuel up during their migration. Targeted conservation easements are another way to prevent development and sprawl on large pieces of private land on migration corridors.

A variety of groups, from conservation organizations to energy companies, have worked with landowners to retrofit their fences and make them easier for animals to cross. Another exciting way to protect migration corridors is by building highway overpasses or underpasses. And that can help to reduce collisions between vehicles and deer, for example, during migrations, when they’re crossing highways in great numbers.

There are also discussions of other ways to keep development outside of key migration corridors. Sometimes just shifting it a short distance to one side or the other will allow the animals to continue to move through. And there might be innovative solutions yet to come, since this is a relatively new field where we’re just getting a clear picture of what these migrations look like and starting to think about how to keep them intact for the future.