Photograph by Charlie Hamilton James
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Bison and elk share winter ranges in Greater Yellowstone—these are in the National Elk Refuge near Jackson, Wyoming. Both can carry brucellosis, a threat to cattle. But elk are prized as game, whereas thousands of Yellowstone bison have been slaughtered in Montana because some consider them a menace.

Photograph by Charlie Hamilton James

How Ranching and Hunting Shape Protections for Bison and Elk

Both species can carry a much feared disease. But when they wander beyond Yellowstone's boundaries, only one is welcome.

Editor’s Note: This story accompanies the May 2016 issue of National Geographic magazine, devoted entirely to America’s first national park. Find more at

Wild animals do not recognize park borders. Two of Yellowstone’s iconic species, bison and elk, spill seasonally—and naturally—beyond park boundaries looking for food. One is welcome. The other is not.

Two years ago, Yellowstone’s chief scientist Dave Hallac gazed north from a sagebrush-covered rise near Mammoth Hot Springs across the park border into Montana. Musing aloud, he asked:

“What would happen, do you think, if we managed our migratory elk the same way we’re forced to manage bison? What if we chased elk back into the park on horseback to prevent them from leaving? What if we rounded up elk into corrals and sent them to slaughterhouses? What if we allowed pregnant elk mothers to be shot just a few weeks before they were due to give birth? Do you think there would be public outrage?”

Ranchers in Montana worry that their cattle—mixing on public grazing lands with wild bison from the park—could become infected with brucellosis, a bacterial disease that can cause pregnant cows to abort their calves. For those ranchers, infection could result in costly quarantines and restrictions on trading cattle and shipping them to market.

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A Yellowstone bison held temporarily at Ted Turner’s Flying D ranch is retested for brucellosis. When two of the ranch’s own commercial bison recently tested positive— infected by wild elk grazing the same pastures—they were euthanized and then necropsied at a lab in Bozeman, Montana. 

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A bison raised on the Flying D ranch near Bozeman, Montana, is put down after showing possible signs of brucellosis, a serious disease transmissible to cattle. Whether Yellowstone’s wild bison pose a similar threat is a matter of heated controversy.

Here’s the irony: Both bison and elk can carry brucellosis. And while bison have been regarded by Montana livestock officials as the primary brucellosis threat, in the past 30 years there have been no documented cases of Yellowstone bison directly transmitting the disease to cattle. Any outbreaks in beef herds near the park have instead been traced to elk.  

But in spite of statistics, the state has taken a hard line, refusing to let Yellowstone bison stray naturally outside the park boundaries. Park managers have been forced, by court order and a bison management plan many see as flawed, to kill and harass creatures they otherwise spend most of their time stewarding with respect and dignity. Since 1985, more than 9,000 animals have been destroyed after crossing Yellowstone’s invisible and fenceless northern and western borders.  

“It’s a big deal bison are still with us,” says Lee Whittlesey, Yellowstone’s park historian. “The protection of the bison as a species, because of their fortunate existence in Yellowstone, is, in the opinion of a great number of us, what saved the animal from total destruction.”  

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A fetus was removed from an infected bison that had been euthanized and necropsied at a Bozeman lab.

Whittlesey refers to the massive slaughter of wildlife, mainly by market hunters, that occurred during the middle to late 1800s. During that time, a continental population of 35 million bison was brought to the brink of extinction. The park, established in 1872, served as a sanctuary for just two dozen survivors. Today some 5,000 bison, beloved by visitors, roam within the park.  

Yellowstone Superintendent Dan Wenk said in a recent interview that concerns about disease mask an entirely different reason for the state to thwart bison migration. He says the truth behind the conflict involves a battle for turf: Members of the livestock industry don’t want cattle to have to compete with bison for the grass on public lands outside the park.  

The public, of course, has its own voice—and every year outrage over the harassing and slaughtering of bison grows. Finally, driven by pressure from citizens, Yellowstone Park and the state of Montana, lead by Governor Steve Bullock, are in the midst of drafting a new management plan that could let bison leave the park in winter and allow a small number to live permanently on nearby national forest lands.

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At Fort Hall, Idaho, outside a sweat lodge where Shoshone-Bannock tribe members gather for purification ceremonies, Leo Teton stands next to a pole ornamented with bison skulls. The animals were taken near Yellowstone in hunts that express tribe members' spiritual connection to the animal and affirm long-standing treaty rights. Bison loom large as sacred animals in traditional Native American customs and rituals.

“When you consider this from a science, economics, public opinion, and commonsense perspective, it makes a ton of sense for Montana to give wild bison from Yellowstone year-round habitat in the state,” says Matt Skoglund, northern Rockies regional director with the Natural Resources Defense Council.

There are no lethal management policies to keep elk from moving in and out of Yellowstone. They largely have free rein in Montana—despite the fact that they carry brucellosis, just as bison do. The reason for the difference: Elk have a vocal fan club within the state’s big-game hunting community.

But the threat of brucellosis remains real. South of Yellowstone, in the state of Wyoming, that threat just takes a different form.  

For more than a century, thousands of elk wintering on the National Elk Refuge near Jackson have been fed artificial grass pellets to keep numbers high in the absence of adequate habitat.  The Wyoming Game and Fish Department operates 22 similar feed grounds.

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At a ranch in southwestern Montana, Robbie Magnan and other Fort Peck tribe members ceremoniously butcher a Yellowstone bison, removing its heart. Surplus park bison were kept at the ranch before going to the Fort Peck Reservation. This male was too dangerous to transport.

But when elk congregate in unnaturally large numbers on feed grounds, the rate of brucellosis infection increases. Wildlife veterinarians warn that these crowded animals become vulnerable to an outbreak of an always fatal chronic wasting disease, a cousin of mad cow disease, that is rapidly spreading west across Wyoming in migratory deer herds.

Some say the solution is to stop feeding elk. But that remedy is roundly opposed by outfitters and guides who benefit from having more elk available for their high-paying clients and fellow hunters.  

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The side of a harvested bull elk and its prized antlers are transported the old-fashioned way—by mule. More than 72,000 hunters came to the lands around Yellowstone and Grand Teton in 2014, many enlisting guides to equip them and lead them to their quarry.

As of this spring, chronic wasting has shown up in deer just miles away from Yellowstone, Grand Teton, and the National Elk Refuge.  

There are no simple solutions. With both bison in Montana and elk in Wyoming, politics and culture trump ecological prescription. “We have the knowledge and wherewithal to be smarter,” Dave Hallac told me when he left Yellowstone to become superintendent of Cape Hatteras National Seashore. “While getting there isn’t easy, it’s only our own unwillingness to think out of the box that is holding us back.”

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Members of the Cody herd traverse the remote Thorofare Plateau, just outside the southeast corner of Yellowstone. The elk bands graze there until early autumn, when snow pushes them out of the mountains.

In a spectacular yearlong event, the National Geographic Channel series America’s National Parks will show you the parks’ natural wonders—both big and small—as you have never experienced them before. Learn more about the series.