Buffalo, Bison

Bison Wild Recolonization Stopped With Slaughter – By George Wuerthner


The bison slaughter is proposed to appease the intractable and unreasonable demands of Montana’s livestock industry to zero tolerance for native bison on Montana soil. All of this is justified in the name of controlling brucellosis, a disease that can cause domestic livestock to abort their first calf.

bison, Yellowstone National Park, Montana wildlife politics
The on-going slaughter of Yellowstone National Park bison is justified on the basis of disease control—namely trying to prevent transmission of brucellosis from bison to cattle. While the potential economic impact brucellosis is real, the likelihood is extremely rare. Photo: EMI- Shutterstock

Bison Slaughter in Yellowstone Begins Again: A Bloody Smokescreen

By George Wuerthner, Originally Published in CounterPunch

Deep snow in Yellowstone National Park is once again forcing bison to seek out winter range at lower elevation. In their search for exposed forage, bison naturally wander to snow-free lands outside of the park. Unfortunately for the bison, once they leave the park, they are killed by the Montana Dept. of Livestock ostensibly in the name of brucellosis control.

See the documentary, Hear the Buffalo

Even worse, the National Park Service is participating in this slaughter of native wildlife. Just this past week hundreds of bison were herded into corrals INSIDE Yellowstone National Park where it is anticipated that at least some of them were be killed.

The bison slaughter is done to appease the intractable and unreasonable demands of Montana’s livestock industry to zero tolerance for native bison on Montana soil. All of this is justified in the name of controlling brucellosis, a disease that can cause domestic livestock to abort their first calf.

Such a slaughter would be bad enough if Montana’s stockgrowers were paying for it out of their own pockets, but both the state and federal agencies involved in this slaughter program are taxpayer funded. If the livestock industry had to pay for these machinations themselves, it is doubtful there would be a brucellosis eradication program, much less an active harass, capture and slaughter program.

Thus far this winter more than 100 bison have been killed, and more are likely to die unless policies are changed. In the winter of 2006/2007 more than 1600 bison were killed. And since the first bison was killed in 1985, nearly 6800 wild bison have been slaughtered outside of the park.

No reasonable solution is possible as long as the livestock industry is in charge, in part, because disease control is not the real issue—rather the slaughter of bison is as much about keeping wildlife bottled up in Yellowstone Park and off other public lands as anything to do with protecting Montana’s livestock from disease.


The on-going slaughter of Yellowstone National Park bison is justified on the basis of disease control—namely trying to prevent transmission of brucellosis from bison to cattle. While the potential economic impact brucellosis is real, the likelihood is extremely rare.

There are two major reasons for eliminating brucellosis from livestock. The first is that the bacteria, Brucella abortus, can cause cattle to abort their calves.

Beyond this obvious loss of a calf to the rancher, current government policy also requires any herd found to contain infected animals to be quarantined and eventually slaughtered, representing another loss to any ranching operation which has invested in building a reputation based on a quality herd.

Also livestock producers in states that are brucellosis-free can avoid mandatory testing of animals shipped across state lines. However, both of these last regulations could be altered.

For instance, there is no reason why an entire state should lose its brucellosis-free status simply because one cow or even a few herds in the state test positive for brucellosis. This is a self-created problem that could easily be solved by modest modification in regulations. The problem isn’t with bison and brucellosis, rather the USDA’s Animal and Plant Health Inspection Service (APHIS), the government agency in charge of brucellosis control remains inflexible in its approach to dealing with brucellosis. APHIS uses the threat of a loss of state-wide brucellosis-free status as a club to maintain management control over public wildlife like bison. APHIS is a tax funded arm of industrial agriculture whose main constituency is the livestock industry, not the public interest.

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Though mandatory vaccination would help to reduce the brucellosis transmission fears, there are a host of reasons why the brucellosis scare is likely a smoke screen for motives other than a genuine concern about disease. A little background on the disease is worth discussing.

Recall from above that the main concern of livestock producers is that brucellosis can cause a cow to abort its fetus. That would represent an economic loss to the rancher. That’s an understandable concern to any rancher who might lose a few calves, but why is the federal government involved in brucellosis control? The answer has to do with history.

Back in the 1930s the federal government launched its brucellosis containment program to control Bang’s Disease, the name given to the ailment in livestock. Tax payer support was justified on the basis of public health because Bang’s Disease can cause what is known as Undulant Fever in humans for the undulating fever it causes, along with muscular pain.

The main source for human infection was consumption of unpasteurized milk and/or having contact with infected meat. But with the widespread adoption of pasteurization, and a requirement that all dairy cattle be vaccinated, the disease has not been a public health threat since WW11. But once the program was started, and had benefits for the livestock industry, it was impossible to eliminate the public funding of the program. Since the 1930s the government has spent billions of taxpayer funds to eradicate the disease—largely to benefit the pocketbook of cattle producers.


A glaring inconsistency in the treatment of Yellowstone’s bison herd is the fact that elk also carry brucellosis. There are far more elk in the ecosystem than bison, and furthermore, they are more widespread and difficult to control than bison. Indeed, all the known cases of wildlife to livestock brucellosis transmission in the Greater Yellowstone Ecosystem have involved elk, not bison. And even if it were possible to remove brucellosis from bison, as long as elk remain active carriers of the disease, reinfection of wild bison is likely.

There are approximately 100,000 elk in the ecosystem that wander freely among livestock operations without being harassed, captured, and slaughtered. One may reasonably ask why bison are singled out for slaughter, while elk are permitted to move freely throughout the ecosystem.

There are two reasons. One is that elk have a big constituency comprised of hunters and outfitters. The livestock industry has; so far, avoided antagonizing these people by going after elk. However, there are some in the livestock industry that believe elk should be captured, tested, and those with positive reactors, slaughtered as well.

The second reason is perhaps less obvious. But if disease were the primary motivation for killing bison, it would make sense to capture and slaughter elk. However, I believe a good deal of the motivation for killing bison is to prevent bison recolonization of public lands. The livestock industry recognizes bison restoration as a direct threat. If bison became widespread on public lands, competition for forage would arise, and likely lead to reductions in public lands grazing by private livestock.


New research suggests that on-going slaughter is amplifying the presence of deleterious genes in bison created by past genetic bottlenecks. The original wild herd of bison in Yellowstone had a limited founding population, (as have all herds in the West) and unnatural selection over the years that have compounded the occurrence of these mutations.

Symptoms of the disease can include fatigue while running, lactic acid buildup in the blood and ragged red muscle fibers. The bison do not die at birth but may get tired while running, succumb to prolonged winter cold, get fatigued brushing snow aside for feeding, lose out in breeding competition or fall to predators. In fossil evidence, only 5% of the bison had the mutation, while 81% of bison today are found to have these mutations. Continued culling by the Montana Dept of Livestock amplifies these genetic problems further.


Several vaccines that offer some resistant to brucellosis infection have been developed. Although not 100% effective, they do reduce the likelihood of infection considerably and provide quite a bit of protection against brucellosis transmission– 65-75% in field tests. They cost $4 a shot to administer. But Montana does not require mandatory brucellosis vaccination. At present approximately 70% of the state’s cattle are voluntarily vaccinated against brucellosis.

In 2010 members of two of Montana’s largest livestock groups, the Montana Stockgrowers Association and Montana Farm Bureau Federation, have adopted policies officially opposing the vaccination of all sexually intact female calves because they think it’s unnecessary.

While vaccination is not a silver bullet offering complete protection against infection, it would go a long ways towards reducing exposure in any cattle herd, and reduce the presumed rationale for killing bison.


Even without a mandatory vaccination of all livestock, brucellosis transmission between bison and cattle is rare in practice for a host of reasons.

An important point is that many bison do not carry the active disease. One of the distortions perpetuated by the livestock industry and amplified by the media are reports of field tests of bison showing a significant number test “sero positive” for brucellosis. Field tests for brucellosis only demonstrate the presence of anti bodies which are produced upon exposure to brucellosis; however the presence of anti bodies does not necessarily represent active cases. Thus, due to the limitations of the field test, something less than the number testing positive for brucellosis actually have an active infection and represent a potential source of infection for domestic animals.

To put this into perspective, I would test positive for polio because I was “exposed” to polio by vaccination as a youth, but I cannot transmit polio to anyone today. In the rare instances where more complete lab testing for active brucellosis has been done, the percentage of infected bison is always lower than the number reported as sero-positive in field tests.

The livestock industry often notes that 50% of all bison tested are positive for brucellosis without noting that only sexually mature female bison (usually two years or older) can transfer the disease to domestic livestock. This is a much smaller subset of a bison herd—i.e. much less than 50% of a herd. Bison calves, bull bison, and young female bison are for all intents and purposes unable to infect domestic livestock. Thus the vast majority of bison which test positive and are subsequently slaughtered, including all bison calves and bulls that are killed, can in no way pass on the disease to domestic animals.

The primary route for disease transmission results when a bison or any other animal (elk also carry the disease), aborts its fetus and the dead fetus and/or birthing fluids are licked, nosed, or otherwise touched by another animal. The likelihood that this would occur between domestic cattle and wild bison is possible, but exceedingly rare for a host of reasons.

Timing is critical. Brucellosis bacteria are very sensitive to temperature and moisture, and die rapidly when expelled from a body. And any aborted fetus is a tempting meal for a passing coyote, raven and other scavengers. Thus, unless cattle and bison are actively mixing together, it is unlikely that any livestock will come upon an aborted bison fetus with live brucella bacteria.


Bison abortions, if they occur (and they are exceedingly rare under wild conditions), tend to happen in the spring when most cattle are on the home ranch, and long before any cattle are moved to summer pastures on public lands where they might encounter an aborted bison fetus.

Furthermore, few cattle are present over most of the area outside of Yellowstone where bison are currently being harassed and slaughtered. Nearly all public lands grazing allotments near West Yellowstone and north of Gardiner have been closed. Cattle on private lands in the West Yellowstone area are only there in summer. North of Yellowstone beyond Gardiner, there are some small cattle operations on private lands, however, most of these operations involve fenced livestock where mixing of bison and cattle is unlikely. And they are set within a much larger matrix of public land including the Gallatin National Forest and several state wildlife management areas are cattle-free year round.

Thus there is no legitimate reason why bison should not be permitted to wander out of Yellowstone in these areas and to occupy these public lands. Suitable habitat exists on Gallatin National Forest lands in the Eagle Creek drainage and Dome Mountain areas north of Gardiner, as well as west around Horse Butte and north of Yellowstone Park on Gallatin National Forest lands in the Madison and Gallatin Ranges between Big Sky and West Yellowstone. This amounts to hundreds of thousands of acres of potential bison habitat outside of the park.


The disease is really a smoke screen for control of wildlife, and to prevent the restoration of bison to public lands in the West. What the livestock industry really fears is a widespread demand by the public to have its public wildlife like bison given priority on public rangelands. Since bison eat essentially the same forage as domestic livestock, if bison herds were to reestablished there would have to be a dramatic reduction in forage allotment for the private livestock grazing public lands. That, far more than the exceedingly small risk of brucellosis transmission, is what has been driving bison brucellosis politics for decades and has resulted in the death of thousands of America’s wildlife heritage wild bison and the wasted expenditure of millions of dollars of taxpayer dollars.

I got a hint of the real reason for brucellosis politics decades ago when the first bison were killed when they wandered from Yellowstone NP. I was living in Livingston, Montana just north of the park at the time and doing research for a magazine article on the bison-brucellosis issue. I had put a call into the Montana State Veterinarian. For some reason when he got on the phone with me he automatically assumed that I was a rancher.

He said to me, “where do you live?” I said “Livingston.” And he immediately said to me, “Hey you don’t have to worry about brucellosis because you live far enough from Yellowstone that it’s unlikely your animals will get the disease. Beside, the state would won’t lose its brucellosis-free status even if a few herds got brucellosis.”

I was surprised by this last statement because he had repeatedly told the media that the biggest fear for Montana’s livestock industry was losing its brucellosis-free status. So I asked him to clarify.

“Why won’t the state lose its brucellosis free status?” I asked.

He replied, “Oh,” he said candidly, “If any limitations are imposed due to brucellosis status APHIS will restrict that to a few herds around Yellowstone.”

I said thanks for the reassurances, and hung up.

Despite this assertion, the state continued to argue that loss of brucellosis status was a real threat. And has used the brucellosis card as a club to silence and detract the media and others from following the money. And the big money for many ranchers is the potential loss of subsidized grazing on public rangelands if bison were permitted to reoccupy those lands and grazing allotments are closed and/or forage for domestic cattle reduced to accommodate bison herds.


Lest we forget, bison are herd animals that have complex social organization based upon familial ties. The testing and slaughtering of animals continuously reshuffles and breaks these family ties. Cultural knowledge about migration routes, how to defend against predators, and other information critical to the long term health of the herd are lost and/disrupted by present management. The most important thing to remember about bison—they are not domestic livestock—and we should treat them for what they are wild creatures that deserve respect rather than the contempt shown by Montana’s government agencies.


So to summarize, in order for disease transmission to occur, a whole litany of events must transpire. First, the bison has to have the disease. It has to be a sexually mature female bison who then aborts her fetus. The aborted fetus has to be undetected by coyotes, ravens and other scavengers which would quickly consume it. All during this time, the bacteria must remain alive. Finally, a domestic animal has to physically lick or otherwise come in contact with the aborted fetus before the bacteria dies.

The fact that less than a thousand and perhaps as few as 200 cattle occupy the zone of current overlap between bison and livestock makes it easy to establish a buffer zone around the park where all cattle should be vaccinated, and tested regularly for brucellosis. Isolating the test requirements to those animals immediately in the zone of overlap would not create an undue burden on the rest of the livestock industry. This would be far less expensive solution for taxpayers—who are after all footing the bill– than the current test and slaughter of wildlife.


Bison have suffered tremendously from the artificial management that has afflicted the species for more than a hundred years. All founding populations, including the bison in Yellowstone which at one time numbered less than 100 animals, have suffered genetic bottlenecks that have amplified the occurrence of deleterious gene mutations. The first step in overcoming these harmful genetic loads is to permit natural selection to weed out the bison that are less fit. This can be accomplished in two ways. One by allowing natural selection in the form of winter starvation, predators like wolves , and other natural selective processes to continue to whittle away at less fit bison, removing them from the herds.

Beyond that, we need to greatly expand, not reduce, wild bison numbers across the West. One way to enlarge bison herds and avoid future bottlenecks is to expand the public lands available to bison. As previously mentioned, there are significant acreages of land immediately surrounding Yellowstone where bison could recolonize in the Gallatin and Beaverhead-Deerlodge National Forests without significant conflict with private livestock operations if reasonable preventative precautions are followed.

Bison could also find suitable habitat in the Union Gap/Upper Green River country north of Pinedale Wyoming as well as in the Green River Valley/Salt River, and Commissonary Ridge areas of the Bridger Teton NF and BLM lands between Daniel and Kemmerer Wyoming.

In addition, to ensure maximum genetic diversity bison should be reintroduced on to other suitable public lands where extensive public holdings would minimize conflicts with private lands. Among these sites are the Charles M. Russell Wildlife Refuge and Missouri River Breaks National Monument in central Montana, the Red Desert and Big Horn Basin, and the Thunder Basin National Grassland areas of Wyoming, the Snake River Plain surrounding Craters of the Moon National Monument and the drier valleys between the Lost River, Lemhi and Beaverhead Mountains in Idaho, the Book Cliffs/Roan Cliffs region of Utah-Colorado, the Vermillion Basin and Brown Park NWR of NW Colorado and Dinosaur NM on the Colorado-Utah border, the Little Missouri National Grasslands and Theodore Roosevelt National Park in North Dakota, the Buffalo Gap National Grassland and Badlands National Park in South Dakota and the extensive parcels of BLM lands in southern New Mexico.

Brucellosis is a smoke screen. It’s time for citizens to challenge the livestock control of our public wildlife, and to demand that bison be given a bright future by ensuring the widespread restoration of these magnificent animals. Bison are part of America’s wildlife heritage that deserve better than the slaughter house.

George Wuerthner is an ecologist.

After a judge cleared the way for slaughter, Governor Schweitzer halted it for the year, calling for federal intervention…

See NRDC Press Release: No Need for Buffalo Body Count: New Brucellosis Rules Should Force Adaption of Yellowstone Bison Management

Updated 1 March 2023

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