The Chronic Incompletion of Bighorn Sheep Restoration

Owing to their high-elevation haunts and habit of staying well away from the more disruptive tendencies of humans, bighorn sheep were fairly insulated from our first continental wildlife reckoning.

As deer, elk, wild turkeys, pronghorns, and a whole menagerie of birds got caught in the thresher of American progress, bighorn rams were relatively unaffected by farms, factories, and the firearms of market hunters. The exceptions that paid the price in extinction were our lowland sheep, the Audubon subspecies of the lower Missouri and Yellowstone rivers that fed the crews and woodhawks of the steamboat era.

In the high country, mountain men whittled at Rocky Mountain bighorns, while across the Southwest, Native tribes built cultures and cuisines around the horns and meat of desert sheep. The remote habitat of these species shielded them from the industrial-scale losses that decimated their river-dwelling brethren.

When the most virulent influence of humans’ intrusion arrived in bighorn country in the middle years of the last century, it was hard to see at first. It still is. It’s a microscopic pathogen, carried by Old World domestic sheep, goats, and even llamas that New World wild sheep have no natural immunity to fight. Wild sheep that contact domestic livestock often contract what in humans might be considered the barnyard equivalent of the common cold. But with no ability to fight it, that sniffle in bighorns becomes highly contagious pneumonia that becomes fatal respiratory failure in a staggering number of wild sheep from British Columbia to Sonora—and every American state in between.

The effects of Mycoplasma ovipneumoniae (better known as M. ovi) often deliver an ignominious end to an animal that represents the austere purity of wild country. In a perverse way, the microorganism has kept Kevin Hurley in business. The vice president of conservation for the Wild Sheep Foundation (WSF) and former big-game biologist for Wyoming’s Game & Fish Department, Hurley credits M. ovi with keeping bighorn sheep restoration an energetic present- and future-tense challenge. In 2024, WSF raised and directed over $11 million for wild sheep conservation, adding to some $145 million the organization has generated and put into wild sheep conservation in its lifetime. While much of that private-sector investment has gone toward expanding suitable habitat and herds, a sizable percentage is devoted to restoring sheep in places where disease has wiped them out, sometimes repeatedly, over the past 50 years. Over the past century, an estimated 22,000 wild sheep have been transplanted in some 1,500 operations.

“Every once in a while, I wonder: Are we better off now than when the Foundation for North American Wild Sheep [the precursor for WSF] started in 1977?” asks Hurley to no one and to everyone. “If your metric is hunting opportunity, then undoubtedly we have been successful. We are raising the sea level. If your metric is more sheep on the mountain, then I think the jury is out.”

Have we recovered wild sheep? Hurley’s simple answer is no. His more complicated answer illuminates the nuances of managing wildlife in a climate of scarcity, as opposed to the abundance that defines our management of whitetail deer, Canada geese, and elk in many places. The habitat-limited populations of sheep grow slowly and with frequent setbacks. Add climate change, human encroachment, and the wild card of disease ecology and you can appreciate Hurley’s job security.

“But with wild sheep, I look at historic range and suitable range, and they’re not always—or even often—the same. There’s a lot of historic range that can never be reoccupied because it’s no longer suitable.”
- Kevin Hurley - Wild Sheep Foundation Vice President of Conservation 

Kevin Hurley assisted during the translocation from Elephant Mountain to Franklin Mountains State Park in Texas.

A Sliding Definition of Habitat

Disease devastates wild sheep, but it has a cascading effect on wildlife managers who invest limited agency resources in building wild sheep populations only to see them crash for reasons beyond their control. The risk of disease, along with drought, human development, and habitat constraints, have caused Hurley to narrow his field of view.

“As conservationists, we often measure our success by filling the historic range” of wildlife species, he says. “But with wild sheep, I look at historic range and suitable range, and they’re not always—or even often—the same. There’s a lot of historic range that can never be reoccupied because it’s no longer suitable.”

Hurley points to the basin-and-range habitat around fast-growing Las Vegas, Nevada, or the interstate-bisected sky-island mountain ranges of southern California, both of which are historic desert bighorn sheep habitat. In those cases, the habitat is so compromised by wildlife-limiting infrastructure that bighorn restoration is out of the question. It’s historic range, but not suitable range.

“Any time someone wants to put sheep in a place, the first question I have is, ‘Were they there historically?’ Second, I ask, ‘Why did they go away?’ and third, I ask, ‘Is the habitat still suitable?’ If I get three affirmative answers then we’re on our way to sheep restoration. But if not, then we take a step back and look at what has changed.”

Complexities of Modern Wildlife Restoration

The pioneers of wildlife restoration overcame daunting challenges. The science of wildlife management hadn’t yet been invented, so species conservation tended toward either preservation or domestication, with as much time spent in capitol buildings and boardrooms seeking political wins as in the field. When the next generation of conservationists hit its stride, with trap-and-translocation operations planting animals in vacant habitat, missions had the singular purpose and muscularity of a military campaign.

Restoring bighorns depleted by disease combines aspects of both these earlier restoration eras. Intensive monitoring is so intrusive—with capture, testing, marking, and retesting—that it can resemble animal husbandry. Politics, especially convincing decision-makers to invest in sheep restoration, is a big part of contemporary conservation. And the conventional response to a catastrophic disease outbreak is repopulation, which involves the same muscular catch-and-release operations of a previous generation.

But overlaying all that intensity is a hanging question that never bothered early wildlife restorers: Is it worth it?

“Wild sheep management isn’t linear,” says Keith Balfourd, WSF’s director of communications. “In some jurisdictions populations are stable, in others increasing, and in others decreasing. Data suggest that in the 1950s and ‘60s, desert and Rocky Mountain bighorns together amounted to about 25,000 animals. Now we’re pushing 90,000. But it hasn’t been a steady increase. Instead, some years we’re up, other years we’re down, but the trend is positive.”

But Balfourd notes that sheep populations are small everywhere, which is why each additional hunting opportunity is proportionately bigger than for other species. This dynamic is at the root of WSF’s novel and sometimes controversial approach to restoration. Because wild sheep conservation is expensive and uncertain, many state agencies are reluctant to dedicate revenue to their welfare. But the Wild Sheep Foundation has cracked the code on earmarked revenue generation.

By convincing decision-makers—by turns governors, agency directors, or fish-and-game commissioners—to donate special hunting licenses to WSF to auction to the highest bidder, the organization has raised and directed millions of dollars for wild-sheep conservation that has, in turn, created more opportunity for hunters to draw one of the few but increasing public tags.

The arrangement is controversial because it awards rarified hunting opportunities to those with the means to pay. But because auction-tag revenue is reinvested in wild-sheep habitat and management, restoration success generally results in more tags for anyone to draw.

After New Mexico’s Department of Game and Fish invested staff and resources in bighorn management, wild sheep there “went from state listed as threatened to downlisted to delisted, with two full-time sheep biologists and a herd of about 800,” notes Hurley. Now that New Mexico’s sheep herd is pushing 2,600 animals, the state issues more hunting opportunities than ever. Earlier this year, WSF auctioned New Mexico’s statewide Rocky Mountain bighorn tag for a record $1.3 million.

“That money will be plowed back into the sheep program to create even more hunting opportunity,” says Hurley, “but it’s also validation that intentional sheep conservation has real value.”

Keith Balfourd at phase 1 of construction on the Muddy Mountains guzzler project in Nevada, said this undertaking is the largest guzzler ever built for water collection and distribution in Nevada’s history. In addition to receiving funding from WSF and Bergara, the project also received funding from the Nevada Department of Wildlife (NDOW), WSF affiliates, Fraternity of the Desert Bighorn, Nevada Bighorn Unlimited-Fallon, Nevada Bighorns Unlimited-Reno, and Meadow Valley Wildlife Unlimited. 

Limiting Factors

Back in reflective mode, Hurley and Balfourd look across landscapes at impediments to bighorn recovery or factors that make restoration hard or impossible.

“When I look at what’s different for desert sheep versus what Rocky Mountain bighorn need, it’s water,” says Balfourd. “Conservation of desert sheep almost always comes down to a pretty basic truth: No water, no sheep.”

Installing and maintaining guzzlers, which collect and hold water in arid environments, have sustained desert sheep in historic range where natural water sources are scarce and getting scarcer.

Keeping wild sheep away from pneumonia-transmitting domestic sheep and goats is an ongoing challenge in both mountain and desert habitat, says Hurley, who returns to his historic-versus-suitable-habitat differentiation. Wild Sheep Foundation has mapped a 14-mile circle around vacant bighorn habitats. If a domestic sheep-and-goat operation is inside that 14-mile radius, then WSF no longer considers that suitable habitat.

“We have mapped pretty much all the available bighorn habitat across the West,” Hurley says. “And there’s some pretty choice habitat that is both historic and which would be available if not for the presence of domestic sheep and goats, either production flocks or what we call hobby farms—those people who live on 10 acres out of town and have 5-10 sheep and goats for meat or wool or just because they like the idea of small-scale farming. The problem for wildlife managers is that you could put sheep on the mountain, but in the winter they’re coming down near those hobby farms. And all of a sudden, what looked like choice, available habitat is no longer suitable habitat” because of the vector of disease transmission.

One response to managing in a disease-prone environment is to flood the zone with sheep, putting bighorns in all available habitat as a buffer in case a single herd succumbs to M. ovi. That strategy requires constant monitoring and frequent supplemental translocations, but until (if ever) a vaccine for M. ovi in wild sheep is developed, it keeps wildlife managers one step ahead of the disease. Hurley says the strategy may ultimately save one of the original source herds for North American bighorns.

“California bighorns [a subspecies of desert sheep] came to the United States in 1954 from the Junction herd at Williams Lake, British Columbia,” Hurley says. “The first translocation was Steens Mountain in Oregon. Seven states now have California bighorns that descended from that B.C. source.

“But the Junction herd is struggling, and there’s talk that some of these American herds are doing well enough that, 70 years later, they may be able to repatriate the Junction herd. That’s the challenge, but it’s also the promise of wild-sheep restoration. You lose a few, you gain a few, but over time, you are building herds and hunting opportunities and putting more sheep on the mountain.”

“When I look at what’s different for desert sheep versus what Rocky Mountain bighorn need, it’s water. Conservation of desert sheep almost always comes down to a pretty basic truth: No water, no sheep.”
- Keith Balfourd - Wild Sheep Foundation Director of Communications

SIDEBAR

Public Policy of Wild Sheep Conservation

Wild sheep conservation requires timely and directed public policy to grow bighorn herds throughout North America. Reducing competition from feral horses, considering bighorns’ seasonal habitat requirements in agency land-use planning, and researching disease ecology all bear on wild sheep restoration.

In Nevada, with the highest population of desert bighorn sheep of any jurisdiction in either America or Mexico, feral horses and burros are outcompeting native wildlife for water and forage. The Wild Sheep Foundation and Boone and Crockett Club advocate for active federal management of these grass-eating, wetland-damaging invasive ungulates, employing strategies such as adoption, sterilization, and agency-led removal to reduce their numbers. Both conservation organizations call on Congress to fund the $66 million modernization of the U.S. Geological Survey’s National Wildlife Health Center in Madison, Wisconsin. The center is the nation’s only facility dedicated exclusively to the detection, control, and prevention of wildlife diseases. While its most urgent efforts focus on avian influenza and chronic wasting disease in deer and elk, a top priority is also understanding and preventing the transmission of M. Ovi pathogens between domestic and wild sheep.

Similarly, both groups are pushing the establishment of the Wildlife Movement Through Partnerships Act, which would add wild sheep to big-game species included in provisions of Secretarial Order 3362, the so-called Migration Order issued by then-Interior Secretary Ryan Zinke in President Trump’s first administration.

Because wild sheep both migrate seasonally and also foray in designated “movement areas,” the bills would establish conservation priorities for key migration routes and foray areas to minimize contact with domestic sheep and goats.