Wildlife Migrations in the U.S. Sustain Species, Ecosystems, and Economies—but Face Threats

New report details latest science on animal movements, key risks, and recommendations for conservation

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Wildlife Migrations in the U.S. Sustain Species, Ecosystems, and Economies—but Face Threats
A line of brown female elk walk from left rear to right front along a deep path in snow with snow-flecked fir trees, blue sky, and puffy clouds in the background.
Conservation of ancient pathways used by migratory ungulates—such as these elk trekking to their winter range—can help protect these animals and the many benefits they provide to ecosystems and human communities.
Gregory Nickerson and Travis Zaffarano Wyoming Migration Initiative, University of Wyoming

Each year, millions of mule deer, elk, pronghorn, and other large ungulates (hoofed mammals) traverse the vast landscape of the American West. In recent years, GPS technology, in the form of collars affixed to individual animals, has revolutionized scientists’ understanding of these migrations by enabling researchers to pinpoint when, where, and how wildlife moves at a grand scale.

This new and growing body of data is also transforming the work of wildlife managers, land stewards, transportation officials, and policymakers: Since the beginning of 2022, seven Western states have passed legislation to maintain wildlife habitat and movement, marking a seminal moment for connectivity conservation efforts.

Now, a new report from The Pew Charitable Trusts, “How to Conserve Wildlife Migrations in the West,” promotes further integration of the rapidly evolving research with state, Tribal, and federal management and policy efforts. The study details the current state of knowledge about the many long and sometimes remarkable migrations in Western states, examines the role of animal movements in the region’s ecological and economic heath, identifies the most substantive threats to migrating wildlife, and makes recommendations for the long-term conservation of migratory animals and the corridors they travel.

Wildlife managers from the Shoshone & Arapaho Tribes Fish & Game, U.S. Fish and Wildlife Service, University of Wyoming, and The Nature Conservancy.
Wildlife managers from the Shoshone & Arapaho Tribes Fish & Game, U.S. Fish and Wildlife Service, University of Wyoming, and The Nature Conservancy map out a GPS collaring project for ungulates on the Wind River Reservation in Wyoming that will help determine where to undertake conservation measures.
Gregory Nickerson Wyoming Migration Initiative, University of Wyoming

Ungulates often roam great distances in large herds between summer and winter habitats, contributing to food webs that many species rely on by feeding predators, transporting seeds, and otherwise moving biomass and nutrients across the landscape. And along the way they support billions of dollars in economic output from activities such as hunting and wildlife tourism. 

A herd of pronghorn migrating uphill, with apparent difficulty, through snow up to their bellies.
Pronghorn struggle in deep snow in Wyoming’s Upper Green River Basin.
Joe Riis Yellowstone Migrations

Pew’s report found that these migrations are a critical part of the life cycle of most ungulate populations. Animals that migrate successfully are more likely to survive the winter and produce healthier young. But when migration pathways are disrupted, animals cannot access adequate food or important habitat and populations tend to decline.

The study identified several key threats to migratory corridors. In particular, several forms of development, such as transportation systems, urban sprawl, fencing, and energy and mineral extraction operations, can impede migratory behavior and jeopardize the health of wildlife populations. Climate change is also altering the availability of forage at key locations and times. And wildlife-vehicle collisions on the nation’s roads claim the lives of millions of animals—and injure tens of thousands of people—each year.

Seven elk cross a curved, two-lane road in front of a white SUV.
Wildlife-vehicle collisions pose serious risks to motorists and ungulates, such as these elk crossing U.S. Highway 89 north of Jackson, Wyoming, during their spring migration.
Mark Gocke

In light of these findings, Pew developed a set of recommendations to help land and wildlife managers, conservationists, industry, and others better coordinate and direct their efforts to conserve migratory corridors and protect these majestic species. These include expanded use of GPS-informed research; strategies, such as fencing modifications and wildlife bridges and underpasses, to minimize physical barriers along migration routes; improved approaches to land use at the local and regional levels; more robust partnerships with diverse landowners, including incentives for participation in conservation efforts; and adoption of smart energy and mineral development practices.  

The report outlines these steps in detail and shows how, together, they represent a comprehensive approach to conserving migratory corridors, the health of ungulate species, the region’s many and varied habitats, and the character of the American West.

Matt Skroch is a project director and Leslie Duncan is a senior officer with The Pew Charitable Trusts’ U.S. public lands and rivers conservation project.

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How to Conserve Wildlife Migrations in the American West

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The natural spectacle of wildlife migration has beguiled people for millennia—a sense of wonder that continues today. Aristotle and his contemporaries marveled at the sudden disappearance of birds and animals in the fall and their reappearance in spring.1 Now, in the 21st century, science is uncovering fascinating new information about the amazing treks that mule deer, elk, and pronghorn make each year across the American West.

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Western States Use Science to Safeguard Migrating Wildlife

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By the early 20th century across the American West, a host of far-ranging native wildlife had been reduced to a small fraction of their former numbers or geographical extent, with some teetering on the brink of extinction because of overexploitation by early non-Indigenous settlers.

Graduate students in Wyoming tag a mule deer with a GPS tracker to monitor its migration path across hundreds of miles.
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Using the latest technologies involving GPS-enabled collars, wildlife biologists can track big game migrations in real time as animals move—in some cases—hundreds of miles. With this data, researchers are then able to analyze the effects of development, roads, and climatic conditions on animals’ historic migration routes, which can help state and federal agencies make informed wildlife management and development decisions.

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Wildlife Crossings Can Protect Migrating Animals

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Designated bridges and tunnels offer passage for herds, preserve habitats, and keep people safe.

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