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Bighorn Sheep’s Gordian Knot Part I

When I began research for my book Ghostwalker, I learned about the messy politics surrounding reintroductions of bighorn sheep into isolated ranges of the Southwest where they once lived yet disappeared centuries ago. This noble endeavor to reintroduce a once thriving species to these sky islands and basin/range habitats had a dark underbelly. The idea was to eradicate mountain lions from the targeted range beforehand in order to enhance the sheep’s success.

Because bighorns are so fragile, because their restoration has been so fraught, I felt for the sheep. Yet the method seemed arcane at best: the lion through no fault of his own, doing only what lions do, traded for the success of a small herd on a tiny mountain range. The emotions, the circumstances, all very complicated. Therefore I left this vital piece out of my book as it begged for much further research. But the problem stayed with me. This year I decided to do a deep dive into the issue.

But to begin to wrap our heads around bighorn sheep issues, there is a lot to understand. Therefore this will be a series of posts. In my first post, I’ll begin in the area where I live with Rocky Mountain bighorns. All bighorns came to their present delicate circumstance through the same doorway, so beginning with my Rocky Mountain bighorns will lay a good foundation for understanding the more complex issues with desert bighorns.

First, my title. Truth be told I stole it. It’s been used to describe the relationship of mountain lions and desert bighorns. But having spoken with many people and done some research, I do not feel that is an adequate nor comprehensive description of what plagues bighorns. Therefore, here is a Gordian Knot as described by the dictionary:

The Gordian Knot is a legend of Phrygian Gordium associated with Alexander the Great. It is often used as a metaphor for an intractable problem (untying an impossibly tangled knot) solved easily by finding an approach to the problem that renders the perceived constraints of the problem moot.


In 2015, in the Tendoy Mountains southwest of Bozeman, Montana Department of Fish Wildlife and Parks did something unusual—they sold 311 hunt tags for any bighorn sheep in an area of only thirty sheep. Drawing a bighorn ram tag in any western state is akin to winning the lottery. Many hunters put in year after year and probably will never draw a tag in their lifetime. But this fall in Montana was different. Why? Because the Tendoy herd had been struggling for years with a respiratory disease complex with die-offs and low lamb recruitment. The heart-breaking answer the department came up with was to eliminate the entire herd and start anew. What hunters didn’t kill, the department would. Five years later, in 2020, the department announced they’d begin transplanting sheep into the Tendoys again, this time from Flathead Lake.

If you think this is a strange anomaly, it isn’t. Eliminating an entire herd that struggles with a disease complex called Mycoplasma ovipneumoniae (MOVI for short) has been done over and over in the West. But the fault lies with humans, not with the sheep.

Bighorn advocates have compared the disease to how European diseases decimated Native Americans. When European settlers brought their sheep and goats throughout the West, those animals were carriers of these bacterial diseases. Yet the domestics had built up immunity over thousands of years. But for our native bighorns, these were novel pathogens. Between disease, market hunting, habitat loss, and forage competition, native sheep populations plummeted. Original numbers throughout the Western states may have been as high as 1-2 million. By the early 20th century, they were at less than 25,000.

To restore bighorn populations where they were lost, restoration projects began in earnest in the 1960s. The most obvious idea was to move sheep. And that is what wildlife managers did, from one state to another, from one mountain to another, wherever sheep could likely thrive or had been in the past. Canada was a big exporter. So was Wyoming. It was a well-intentioned mass effort. Unfortunately, though somewhat successful, we only added to the problem. Kevin Hurley of the Wild Sheep Foundation described it to me succinctly,

“Somewhere in the future a geneticist is going to look at this and go ‘What the hell were they thinking back in the 70s, 80s, and 90s where they just blended so many sheep from so many sources’.

“The analogy I always use is a daycare. If you put a kid in a room with twenty other snotty-nosed kids, at the end of the day they’ve swapped about as much spit and goo as they can.”

In fact, it wasn’t until around 2007 or later that the lightbulb went off. Up until then, we just didn’t have the technology to understand what was really killing sheep.

When you listen to the wildlife disease experts, the terminology gets way into the weeds. When the question section comes up in zoom public meetings, the one always asked is “Can’t we just create a vaccine?” Yet that is why its called a “pneumonia complex”, because the entire issue is complex. MOVI is what HIV is to aids, it weakens the immune system, leaving it vulnerable to a host of other diseases that might not have otherwise killed a sheep. Biologists called it a “set-up artist”. The fine hairs in the respiratory tract called ciliary are damaged, the sheep are coughing, their lungs slowly destroyed. Some develop nasal tumors which make it harder to slough the disease off, becoming super spreaders (we are all familiar with that term now). Maybe they don’t even succumb to the disease, but being a life-long carrier, a typhoid Mary. The ewes that survive pass the disease along to their lambs through breast feeding. The herd then has adult death and zero recruitment. Usually the die-off of the entire herd, or a large portion, is swift.

Another major problem is that rams, looking for mates and to spread their genetics, do walk-abouts, usually in large circles encompassing 30-40 miles. Even if they begin their journey healthy, they might run into domestic lambs or goats, contract the disease, then bring it back to their herd. One ram came from Colorado into southern Wyoming, traveling over 400 miles and through three different bighorn sheep herds. Wyoming Game and Fish only knew this because the ram was collared and they were alerted by Colorado game agency. Sheep are gregarious—sheep like sheep. They don’t need to touch noses to get infected. They might even be kilometers away if the wind is right. Because Game and Fish had no idea if this ram came into contact with domestic stock, be it a large herd or a hobby rancher, they couldn’t take a chance. This one ram could cost hundreds of sheep lives and devastate entire herds. The ram was euthanized.

From Doug McWhirter 2020 presentation. Lamb Survival in three Wyoming ranges

The deeper microbiologists and veterinarians delve into the bighorn disease issue, trying to find the silver bullet cure, the messier the problem becomes. Although MOVI is a major culprit, there are a whole host of diseases. Although just in the last ten years its been accepted that domestic sheep and goats are carriers, there is now a question if cattle can add to the disease problems as well. Add to that mountain goats who are also susceptible and inhabit the same terrain, the problem thickens. Although we are clear disease is the main issue with sheep die-off, there are still major puzzles to be solved.

The Absaroka mountains have the only bighorn herd in the United States that has never been transplanted into nor out of. It is a pure, native herd with between 3500 and 4000 sheep. Although the historical evidence says that mountain goats were never native to Wyoming, a very few were transplanted in the 1960s for hunting, and have migrated into the Absarokas, sharing similar terrain with the native sheep. From a lot of blood work and studies, at last count in 2020 these native Absaroka sheep had the full compliment of pathogens. In other words, they were all carriers as far as the story told by the captured individuals. And although there have been some ups and downs in the population with disease outbreaks, their population remains stable. The mountain goats, which might present a problem in one area as they did recently in the Teton range, don’t seem to present a problem as far as researchers can tell, with the Absaroka herds. One explanation was given to me by Doug McWhirter, Wyoming Game and Fish biologist who has spent his career studying bighorns.

“Some of these pathogens could still be cycling from being introduced decades before. It tends to cycle in those animals. You could have pathogens that are residing in live animals that they pass down to offspring that don’t kill them under most circumstances, but if they are stressed by a weather event, then their immune systems can be comprised, and then at that point in time those pathogens either spread, or become more virulent and that’s when those impacts can take place.”

Raina Plowright and colleagues simple graph of MOVI crash in bighorn sheep population*

Even though there are no domestic sheep allotments on the forest today, the Beartooths were last retired as recently as 2001, and up untill the late 1980s, the headwaters of the Greybull River as well as Carter Mountain had domestic sheep on the forests. My neighbor who passed away a few years ago and grew up in this valley, born in 1926, once told me there were sheep herders all over the valley. I described a strange log structure I discovered in a nearby narrow drainage once. The drainage led to a high meadow with old campsites littered with rusty tin cans. “There were thousands of sheep up there in the summer. The log structure was probably a food cache.”

The Absarokas are littered with old Shoshone Indian sheep traps as well. Trapper Osborne Russell wrote in the 1830s how he saw thousands of sheep on the mountains surrounding the Lamar Valley of Yellowstone. Our native sheep have been exposed to domestics for a long time. Yet another pristine herd in Wyoming is crashing, probably soon to go extinct. The Whiskey Mountain herd in the Dubois area has never received sheep, but have provided many throughout the Western states. Whiskey mountain was a major supplier from the 1960s through 1990. In 1991 the die-offs began, in multiple stages, and the herd has never rebounded. Although both the Absaroka and the Whiskey Mountain herds carry the complete composite of pathogens, what makes one more resilient than the other? Biologists don’t know, but possibly environmental factors come into play—weather, food stresses, minerals like selenium, the jury is still out.

With so many unknowns, wildlife managers and conservation advocates are focusing on what they can control. Where it used to be predator controls (and still is in many respects. More on that later), the main focus has shifted to attempting to control separation between bighorns and domestic sheep and goats. That requires producers to acknowledge their sheep are the problem carriers, and then get them on board. One strategy has been offering to retire allotments, or switching allotments to non-problem areas.

Believe it or not, the expansion of grizzlies and wolves has presented real opportunities for bighorn sheep. Permittees in some circumstances are more willing to take the cash offers from private organizations to retire their grazing allotment. Yet the code of the West that enshrines livestock and private property owners has, in my opinion, strangled some of this progress. Take for instance the story of Josh Longwell. Longwell had long been in disputes with federal agencies over grazing, right-of-ways, and wildlife. As retribution, which some might call “wildlife terrorism”, Longwell abandoned grazing cattle on a high elevation grazing allotment in the Owl Creek Mountains and substituted domestic sheep, knowing they’d co-mingle with native sheep. For the Game and Fish, the risk was great, and an infected ram from the Owl Creeks that rubbed noses with Longwell’s sheep could walk-about over to the Whiskey Mountain herd and even north towards the Cody area. The Governor approved an emergency early season and licenses issued for up to 34 sheep. Longwell smugly declared this was an issue between private property and wildlife. And he may have characterized it correctly, and the government caved.

Organizations that have fought hard and long to restore bighorn sheep throughout the West have long tried to work cooperatively, versus litigating. And that is a good avenue to begin. But when it comes to the most sensitive species, an iconic species with multiple strikes against it that we are trying to restore, there are limits. Longwell represents one of those.

Kevin Hurley started our interview with a line that sums up the life of a bighorn sheep.

I go back to the early 80s, Tom Thorne, he was our wildlife vet back then. I’ll never forget the article he wrote back then in Wyoming Wildlife magazine. It was called ‘Born Looking for a Place to Die’. The whole point was they live in tough country but they’re pretty wimpy, respiratory speaking.

*Ecology Letters (Plowright, Raina K., et al. “Age‐specific infectious period shapes dynamics of pneumonia in bighorn sheep.” Ecology letters 20.10 (2017): 1325-1336.)


Stay tuned for Part II.