Places We Protect

Pioneer Mountains to Craters of the Moon


A pronghorn antelope standing in an open grassland.
Idaho Pronghorn Pronghorn moving through the migration corridor of central Idaho © Steve Dondero

Working with ranchers to protect one of the longest pronghorn migration routes in the West.



From the Pioneer Mountains to the Craters of the Moon lies a relatively unknown and largely unspoiled natural area in Central Idaho. Spanning 2.4 million acres of diverse terrain, including lava beds, high desert, rivers and alpine forests, the Pioneers to Craters area was identified by TNC scientists as one of the most climate-resilient places in the Pacific Northwest. At its lower edge is a sagebrush sea dotted with springs and aspen groves. At its high point is Idaho’s third highest mountain peak. Wildlife thrive across this diverse range, among them migrating pronghorn, wolverine and greater sage-grouse.

It is against this backdrop that generations of ranchers and farmers have made homes and livelihoods, guided by a respect for the land and what it provides. In the early 2000s, residents, government agencies and nonprofits took on the monumental task of conserving much of the private land in the area through an effort known as the Pioneers Alliance. TNC Idaho set a goal of conserving 100,000 acres of private lands that were critical connections to public lands in this area.

To date, TNC and its partners in the Pioneers Alliance have conserved more than 95,000 acres — closing in on the overall goal and vision to keep the Pioneers to Craters whole, thriving and resilient to climate change.


Limited Access

This landscape is a mix of public wild lands and private working lands.


2.6 million acres

Explore our work in this region

On this sagebrush prairie of the Pioneers-Craters, pronghorn does watch for signs of spring—the melting snow and the sprouting of nutrient-dense vegetation. They are preparing to move west from their wintering range into the verdant valleys at the foot of the Pioneer Mountains.

Timed just right, the wind becomes their friend and they traverse the emerging green wave of vegetation that will sustain them for birthing in spring. This journey east to west stretches more than 80 miles each way. It is one of few long-distance mammal migrations still viable in the lower 48 states.

Studying Pronghorn Migration

Scientists and wildlife biologists first tracked this journey in 2008. Ten pronghorn does were captured and fitted with GPS collars. The study of the migration continued for another two years, yielding findings that would guide and manage decisions such as removing fencing that impeded migration.

Tess O’Sullivan, then the program director with the Lava Lake Institute for Science and Conservation and now a conservation manager for The Nature Conservancy in Idaho, led the project. The migration study was conducted in partnership with the Institute, TNC Idaho, the Wildlife Conservation Society, the Idaho Department of Fish and Game, and a coalition of local ranchers and conservation NGOs called the Pioneers Alliance.

“The information was so powerful. With old wildlife studies, you ended up with a few dots on a map, with the newer more precise GPS technology we could follow the exact movements of the pronghorn from start to finish,” recalled Tess. “It allowed us to truly learn how far they went, how fast they went and where there were pinch points or very narrow areas where they concentrated.”

As they travel east to west, they will walk single file passing through the Craters of the Moon National Monument, north of the lava flows and the route’s narrowest constriction. Entering the Pioneers, they pass directly through a critical piece of land known as the Cenarrusa Ranch before they fan out across their summer range, where they give birth to and raise pronghorn calves.

A wide-open landscape with scrubby plants and hills in the distance.
Cenarrusa Ranch The ranch contains critical wildlife habitat and migration corridors for a myriad of wildlife that include big game and sage grouse. © Tess O'Sullivan/TNC

Tracking Study Yields Big Results

The insights illuminated by the tracking study combined with TNC’s scientific analysis that identified the Pioneers-Craters as one of the most climate resilient areas in the region—based on its incredible topographic diversity and largely undeveloped state—provided crucial data points from which TNC Idaho created a decades-long vision to protect more than 100,000 acres between Craters of the Moon National Monument and the Pioneer Mountains. That vision included the protection of the 8,891-acre Cenarrusa Ranch.

TNC Idaho secured an agreement to purchase the property in 2016, the first step in ensuring the natural landscape would continue to provide open passage and quality forage for the pronghorn and other wildlife that depend on it. Importantly, for TNC, this vision includes the human communities who have a mutual dependence on this landscape. Purchasing the ranch was the first step toward long-term protection. We needed to find a partner to help us conserve this property, a partner who could purchase and manage conservation easements on the land to protect it for future generations.

Conservation through Collaboration

We found that partner in the Bureau of Land Management. With funding from the Land and Water Conservation Fund, the agency stepped forward this winter to purchase the easement. In the coming years, we’ll search for a conservation-minded landowner to purchase the ranch.

The Cenarrusa Ranch is a key piece in a larger vision of conservation in the Pioneers to Craters and an ideal example of TNC Idaho’s approach to conservation where science, community and collaboration come together to conserve Idaho’s great places and iconic wildlife.

With protections in place for the Cenarrusa Ranch, we are now within reach of our goal for the Pioneers-Craters

Your Chance to Give Back

The Nature Conservancy is working to protect Idaho's wild places for people and nature.