CASPER, Wyo. — In a pen surrounded by 8-foot-high fences, at a research station by the side of a winding canyon road in southeast Wyoming, stand seven elk that are going to die.
The creatures don't look sick yet. Their caramel-colored fur still covers round bodies the size of small horses. They run back and forth with each other and two bighorn sheep ewes that share their pen, greedily eating food offered at the gate. How long they'll last is a question researchers can't answer.
Each animal has been exposed naturally to chronic wasting disease, a killer that can lie dormant for years before corroding their brains with tiny, sponge-like holes.
But these female elk are unlike most others. They have rare genetics, which might just prolong their lives.
The cow elk are one small piece of a complicated puzzle that has confounded researchers, scientists, wildlife managers and federal disease specialists for decades, threatening deer and elk in more than a dozen states and three Canadian provinces.
At stake is Wyoming's identity. The Cowboy State's iconic herds not only draw thousands of hunters and wildlife viewers each year, they're why many people live here in the first place.
The puzzle started in the 1970s in a Colorado State University lab. Late-CWD researcher Beth Williams noticed that some deer acted disoriented and weak before they eventually died. She diagnosed the killer as chronic wasting disease, a cousin to "mad cow disease," scrapie in sheep and the always-fatal Creutzfeldt-Jakob disease in humans. Her discovery led to a nationwide panic over fears it could spread to humans, followed by relative apathy when it seemed more and more like it would not.
Now the seven elk behind the 8-foot fence could possibly be the key, even in the smallest sense, to solving the mystery of a disease that first appeared in Wyoming in the mid-1980s and is creeping northwest, permanently infecting everything it touches.
"As one question is answered, two more pop up," said Hank Edwards, wildlife disease specialist for the Wyoming Game and Fish Department. "It is frustrating. It's hard to get a handle on controlling this disease when there's so much left to learn."
After decades of work, wildlife managers are, in some ways, starting over in figuring out how to manage the disease. The Centers for Disease Control and Prevention still don't recommend humans eat an infected animal, but there have been no cases of transmission. Nor did the disease initially tear through herds as quickly as first predicted.
But that's all starting to change. New models are showing that in the long term, mule deer numbers, particularly in central Wyoming, could plummet.
Instead of raging through like an ancient plague, the disease kills slowly, taking years or even a decade, and spreading in ways no one quite understands. So Wyoming wildlife managers and researchers are regrouping, working at ground zero with new information and seeking input from the public as they race to grasp the full impact of — and possible solution to — one of the most deadly wildlife diseases facing the state.
One crisp morning in late winter 2016, cattle rancher Peter Garrett opened his front door and found a four-point deer leaning against the side of his house.
The rancher's dogs — black and white McNabs — raced outside without noticing the buck. Startled, Garrett tried shooing the buck, but the animal just stood and kicked, then laid back down.
Ten minutes later, the buck was still there. Nothing could make it move. Not the dogs coming back. Not Garrett. Not his wife.
"Maybe he was looking for warmth against the house," Garrett said. "It was right there where the sun beats and by the fireplace."
The Garretts ultimately called Game and Fish, as they always do when they find sick deer on their ranch, which sprawls on both sides of Highway 487 southwest of Casper. When the game warden arrived, he removed the buck. Later, he told Garrett that it tested positive for CWD.
It wasn't the first.
More and more deer were dying on and near Garrett's ranch in what Game and Fish calls Hunt Area 66. It has the inauspicious distinction of carrying the second-highest rate of CWD in the state.
But the mule deer herd is part of Garrett's life. It helped keep the lights on in his family ranch 50 years ago when he and his new wife were short on cash and worked as outfitters on the side. It kept them alive when the couple couldn't afford to eat the beef they were raising for market. Shed antlers cover chandeliers in his log home tucked at the base of a mountain. Mounts of some of the deer he and his sons have shot nestle in corners.
Garrett, 70, has spent years working with Game and Fish on habitat projects in the area to try to improve food for the deer. His list of accolades from organizations such as Game and Fish and Wyoming Stock Growers Association for good stewardship of his land grows longer each year.
But a solution still eludes him.
"I don't like it, but what can you do?" he said. "Our deer numbers — when my kids were in school, you could count 400 to 500 between here and the highway, and now you're lucky if you count 50."
"And that's on a good day," said his wife, Ethel Garrett. "Now it's 10 or 15. Then we complained about too many deer. But we'd like to have a happy medium."
Game and Fish estimates that in that particular herd, about 23 percent of the buck deer will die in less than two years.
Chronic wasting disease is certainly not the only wildlife illness to confound specialists.
But finding a solution is particularly tricky because, like Alzheimer's or Parkinson's, CWD can't be targeted and killed like a bacteria or virus. It doesn't have a cure or vaccine. It doesn't die if you simply cook it long enough or let it sit in the sun.
"Diseases like brucellosis, we know how to work with that," said Scott Edberg, deputy chief of Game and Fish's wildlife division. "There's no silver bullet, but we're trying to find one. It's not like a common cold."
Edberg, Hank Edwards, the disease specialist; Dr. Mary Wood, the state wildlife veterinarian; and a handful of other researchers and wildlife experts in Game and Fish are all part of a CWD think tank of sorts. They meet periodically to talk about new research, changes in the herds around the state and new cases of the disease.
At a February meeting at the Tom Thorne and Beth Williams Wildlife Research Center at Sybille, they explained CWD's complexities and its infamous history in Wyoming.
CWD, Edwards said, is a prion. That means it's a protein, a natural part of a body, which mutates and becomes infectious. The mutated protein then attacks other cells living in the body's nervous system. As it forms tiny, sponge-like holes in an animal's brain, the animal begins to act lethargic, become emaciated and drool excessively before eventually dying.
Chronic wasting disease itself affects only mule and white-tailed deer, elk and moose in Wyoming, but there was a time after the disease was first discovered in southeastern Wyoming in 1985 when fears ran rampant.
"The threat that this prion disease could go to humans, that really drove a lot of our research and awareness, but now, based on our information, we don't believe the disease will go to humans," Edwards said. "I think it is time to switch the focus away from human health to herd health."
Yet for every question researchers seem to have answered, they find new ones that are more confounding.
The prions that cause scrapie, for example, have changed over time, forming multiple strains, said Wood. Something is keeping the strains from crossing into other species; researchers don't know what that biological reason could be and whether it's strong enough to continue to prevent crossover.
Researchers also don't know why CWD seems to kill deer at higher rates than elk or moose or why it kills more males than females.
It spreads by contact, researchers believe, but it also sheds off animals and can likely live in the ground for more than a decade. So far only incineration above 1,000 degrees, lye and bleach can actually kill the prion.
"What we don't know in a free-ranging herd on the landscape is: How significant is animal-to-animal transmission versus environment-to-animal transmission? We don't know what's going on on the landscape," Wood said. "That makes it hard. Knowing key transmission is the most important thing to model what is going to work."
The disease is always fatal but takes more than a year and a half, depending on genetics, to actually kill an animal.
"Along those lines, how high does CWD prevalence get in a herd? How much can a herd withstand? Every herd is going to be different," Edwards said. "As time goes on, we will figure this out, of course. It's a big question of how much CWD these herds can stand without seeing a pretty big population reduction."
Scientists are starting to get a better idea. Research by Melia DeVivo, a former University of Wyoming graduate student, concluded that the mule deer bucks in Hunt Area 65 southeast of Casper have a 40 percent prevalence, which means if nothing changes, the herd could be essentially gone in about 50 years.
Down the highway from Peter Garrett's ranch, on a cold, windy, late February day, a helicopter capture crew netted, tackled and carried mule deer two at a time to a staging station for testing.
Game and Fish biologists and a host of volunteers and researchers stood by, waiting for each blindfolded creature. The female deer had their ages and body conditions recorded and a GPS monitoring collar fixed around their necks. Wood, the wildlife veterinarian, took rectal tissue samples to test for CWD.
The study wasn't specifically for CWD research — biologists are trying to learn more about the herd — but Area 66 is west of Hunt Area 65, the mule deer herd with the highest prevalence of CWD in the country.
"As CWD continues to proliferate in Wyoming, we've seen this inevitable westward march," said Justin Binfet, Game and Fish's regional wildlife coordinator in Casper. "It's a good chance to look at what CWD prevalence is doing in a herd that is not known for being long exposed but is developing into a pretty significant prevalence."