Questions & Answers about Bison Management

Management

Who manages Yellowstone bison?
The Interagency Bison Management Plan (IBMP) guides the management of bison in and around Yellowstone National Park. Five federal/state agencies and three tribal entities implement the plan.

Why are bison killed every winter?

  • Bison are killed because there are too many animals in too small a space. Yellowstone encompasses a limited amount of habitat and Montana only allows very limited numbers of bison in small areas adjacent to the park.

  • Allowing the bison population to grow indefinitely will cause overgrazing and possibly mass starvation of animals in Yellowstone, as well as larger migrations and greater conflict outside the park.

  • We don’t know of any bison conservation herds in North America that are naturally regulated: all require population reduction by capture and removal or hunting.

  • Yellowstone bison currently reproduce and survive at relatively high rates compared to many other large, wild, mammal species. The bison population increases by 10 to 17% every year (that’s ten times faster than the human population grows worldwide).

  • Currently, predation by bears and wolves has little effect on the bison population. Bison are massive animals that defend themselves as a group, making them more difficult to attack than animals such as elk.

  • Hunting outside the park has not been effective at limiting bison numbers because concentrated hunting pressure along the park boundary often causes bison to return to the security of the national park where hunting is prohibited.


How many bison will be killed this winter?
For the winter of 2016/2017, IBMP members collectively decided to reduce the bison population. In order to accomplish this, 900 to 1300 animals must be removed through hunting outside the park and capture/shipment to slaughter at the Stephens Creek facility.

Aren’t bison protected as our national mammal?
No: that designation did not provide any special protection to bison. Read more about the National Bison Legacy Act.

Why do bison leave the park?
Bison migrate to lower elevations in search of food during winter, just like bighorn sheep, elk, mule deer, pronghorn, and many other animals. They return to the park’s higher elevation grasslands to feed during summer.

Why do states treat bison differently than other wildlife when they leave the park?
Bison are not allowed to move freely outside Yellowstone due to fears they might transmit brucellosis to cattle (see below for more info), and out of concerns about competition with cattle for grass,human safety, and property damage. Elk are also infected with brucellosis, but their movements outside the park are not restricted. State governments control the management of wildlife outside Yellowstone (unless a species is federally listed as threatened or endangered).

Why don't you force surrounding states to change their policies?
Outside Yellowstone, states manage wildlife and Yellowstone cannot force them to tolerate more migrating bison.

Why don’t you just ignore the IBMP and let the bison go?
Doing nothing is not a realistic option. Allowing the bison population to grow indefinitely will cause overgrazing and possibly mass starvation of animals in Yellowstone, as well as larger migrations and greater conflict outside the park.

How are bison captured?
On behalf of the IBMP, bison are captured near the north boundary of Yellowstone as they migrate out of the park. Fences guide them into enclosures, so they wander in on their own or are sometimes pushed in by riders on horseback. For more information on the capture and shipment process, take a video tour of the Stephens Creek facility.

How are bison killed?
We transfer captured bison to our tribal partners who have them shipped to slaughterhouses.

What happens to the meat?
Our tribal partners distribute the bison meat and hides to their members.

Does Yellowstone profit from shipments of bison?
No: we receive no payment for bison shipped from our capture facility.

Are animals abused at Stephens Creek?
No. The safety of people and animals is our top priority at Stephens Creek. The Humane Society has evaluated the operation twice, and each time we've adopted their recommendations. These have included creating visual barriers (plywood walls) so the animals can’t see out of the corrals, and eliminating all nonessential people from the catwalks during processing. Two old photos are often used to falsely depict our handling practices at Stephens Creek. One shows a bison being held with a nose ring during brucellosis testing, a practice we haven’t used in many years (we now have a hydraulic chute that holds the animals relatively still during testing). The second shows a bison being carried by a front-end loader: a photo that was taken outside the park, most likely after a bison was shot by a hunter or hit by a car. Adult bison can be very large and heavy and often times require heavy equipment to move carcasses from vehicle accident scenes. For a detailed view of the capture and shipment process, take a video tour of the Stephens Creek facility.

Does culling put the population at risk?
No. Yellowstone’s bison population has grown steadily over the last 45 years: from 500 animals in 1970 to 5,500 in 2016. Along with elk, bison are the most numerous large mammals in Yellowstone, and periodic culling will not alter that fact. The sizes of most wild ungulate populations in North America are limited by hunting and/or captures and removals.

Are you catering to the livestock industry?
We are legally obligated to follow the directives of the the IBMP. Each member of the IBMP has a different perspective on the conservation of wild bison, so conflict resolution is an integral part of the management strategy. We would like to reduce the need for capture and shipment to slaughter, but that would require changing the current bison management plan and agreement from all members of the IBMP.

Brucellosis


What is brucellosis?

  • Brucellosis is a bacterial disease that induces abortions or stillbirths in infected animals, but does not kill them. For ranchers, brucellosis has an economic impact because it affects the reproductive rate and marketability of their animals.

  • Up to 60% of Yellowstone bison test positive for exposure to brucellosis (depending on age and sex).

  • Brucellosis has been eradicated in cattle herds across most of the United States. Bison and elk in the Greater Yellowstone Ecosystem persist as one of the last reservoirs of infection.

  • Brucellosis was introduced to Yellowstone bison and elk by domestic cattle in the early 1900s.

Is brucellosis really a threat?

Yes. People both understate and overstate the risk of brucellosis transmission. Transmission of brucellosis from bison to livestock is possible because in late winter, bison migrate to low elevation areas outside the park where livestock are concentrated. At this time, bison are late in their pregnancy: the most probable time for infected animals to abort fetuses that might be found by other animals. The fact that there's never been a documented transmission of brucellosis from Yellowstone bison to cattle does not mean it couldn't happen. Rather, it’s a testament to the diligent management efforts put forth by the state of Montana and the National Park Service to prevent co-mingling of bison and cattle during the time period when transmission is most likely.

Do other animals carry brucellosis?
Yes. Over the last two decades, nearly 20 livestock operators in the three states surrounding Yellowstone discovered brucellosis in their animals. In each case, wild elk transmitted the disease. However, the state of Montana allows elk to move freely outside Yellowstone: a freedom that bison deserve, but have been denied.

Why don't local ranchers vaccinate their livestock?
They do, but there is no vaccine that’s 100% effective at reducing abortions due to brucellosis or eliminating the potential of infection from wildlife.

Why can't bison that test negative for brucellosis be allowed to live?
Identifying animals that do not harbor the bacteria is difficult and requires many months or years of quarantine: a single test is not enough. For more details, read the Environmental Impact Statement about our proposal to establish a quarantine program for Yellowstone bison.

Why can't bison be vaccinated against brucellosis?

  • Vaccinating wild bison against brucellosis with existing vaccines would not substantially suppress the disease and could have unintended, adverse effects on the bison population in Yellowstone.

  • There is no easily distributed, highly effective vaccine: current vaccines would only create a 10 to 15% reduction in infection, and immune protection is short-lived.

  • Even if we reduced the prevalence of brucellosis in bison, they could be re-infected by elk.

  • For more details, read the final Environmental Impact Statement that evaluated the potential of remote vaccination of bison.

Alternatives


Are there alternatives to capture and shipment to slaughter?
In the history of North America, only humans, disease, predation, and starvation have successfully controlled bison numbers. Hunting outside the park is the preferred method for controlling the population today, but bison need greater access to land in order to disperse beyond our boundaries and pioneer new areas. Currently, the area where bison can be hunted is very small, and bison often respond to the hunting pressure by returning to the security of the national park (where hunting is prohibited). Our capture and shipment operation makes up the difference when hunting outside the park fails to meet reduction targets set by the IBMP managers.

Why can't Yellowstone ship live bison to other areas?
Right now, it’s against state and federal laws to move wild bison exposed to brucellosis anywhere except to meat processing and research facilities. We’ve proposed a quarantine program for bison, but livestock agencies and producers have opposed the plan. After completing a rigorous quarantine testing protocol, brucellosis-free animals could be sent alive to other public, private, or tribal lands. Quarantine would reduce the need for capture/slaughter operations, and it would promote an even more robust population of Yellowstone bison across the country.

Why can't hunting control the population?
To date, hunting outside the park has been ineffective at limiting bison numbers. The area where bison can be hunted is very small, and bison often respond to concentrated hunting pressure along the park boundary by returning the security of the national park where hunting is prohibited. For hunting to become more effective, bison need greater access to public lands outside the park, like wild elk and other animals, so they can disperse beyond our boundaries and pioneer new areas.

What about fertility control in bison?
No fertility control methods that are affordable, easily delivered, highly effective, and reversible are currently available for delivery to wild bison spread across a vast landscape. Fertility control could have unintended, adverse effects on the bison population in Yellowstone.

 
 

Last updated: February 1, 2017

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