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

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.

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. 

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.

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.