Bison Management

A nursery group of bison cows and calves makes its way through Lamar Valley. Due to high rates of survival and reproduction, the bison population increases by 10 to 17% every year: ten times faster than the human population grows worldwide.
A nursery group of bison cows and calves makes its way through Lamar Valley. Due to high rates of survival and reproduction, the bison population increases by 10 to 17% every year: ten times faster than the human population grows worldwide.

NPS / Neal Herbert


Success & Controversy

The protection and recovery of bison in Yellowstone is one of the great triumphs of American conservation. In 1902, after years of market hunting and poaching, there were only two dozen bison left in Yellowstone. Over the next hundred years, park employees worked to bring this species back from the brink of extinction. We succeeded, and now face the challenge of helping to manage a healthy, rapidly growing population of bison that sometimes roams beyond our borders onto private land and land managed by other agencies.


Yellowstone’s bison population is growing, the park’s borders are not.
Allowing the bison population to grow indefinitely could result in overgrazing in certain areas and possibly mass starvation of animals in Yellowstone, as well as larger migrations and greater conflict outside the park. Due to high rates of survival and reproduction, the bison population is currently increasing by 10 to 17% per year. Predation by wolves and bears has little effect on bison numbers. However, Yellowstone encompasses a limited amount of habitat and bison are not allowed to migrate freely outside the park like deer, elk, and other animals.

The state of Montana treats bison differently than other wildlife.
Bison are not allowed to move freely outside Yellowstone due to fears by livestock interests that they might transmit brucellosis to cattle and compete with cattle for grass, as well as concerns for human safety and property damage. These fears have resulted in Montana legislation that prohibits moving live bison from the park to other conservation areas. For long-term conservation, Yellowstone bison need access to habitat outside the park, similar to other migratory wildlife like elk (another species that carries brucellosis).

Hunting inside the park is not an option.
Hunting is prohibited in Yellowstone, which is why the park offers some of the best wildlife viewing in the world. A few groups want to open the park to bison hunting, but Yellowstone National Park managers strongly oppose this idea. Allowing hunting in Yellowstone would affect the behavior of animals and drastically change the experience people expect when they visit. This is not the future we want for Yellowstone, and we don't believe it's the future the public wants either.

Eight groups play a role in making decisions about Yellowstone bison.
In 1995, Montana sued the National Park Service because bison were migrating out of the park on to state lands. A court-mediated settlement reached in 2000 created the Interagency Bison Management Plan (IBMP), which set a population target of around 3,000 animals and established a cooperative effort to manage bison in and around Yellowstone. If you care about bison, we encourage you to learn more about the agencies and tribes that play a role in deciding their future.

Bison need to be managed.
Until there is more tolerance for bison outside Yellowstone, the population will be controlled by hunting outside the park and capture near the park boundary. Captured bison are transferred to Native American tribes for slaughter and distribution of meat and hides to their members. For 2019, the IBMP partners agreed to reduce the population by 600 to 900 animals using both hunting and capture. We understand that many people are uncomfortable with the practice of capture and slaughter. We are too, but there are few options at this time. Along with our IBMP partners, we’re pursuing alternatives like quarantine and expanded tolerance outside the park that would reduce the need for capture and shipment to slaughter.

Our Goals

We work to maintain a viable, wild, migratory population of our national mammal.
Yellowstone provides one of the few places where bison live much like their ancestors did: unfenced, and unprotected from harsh winters, drought, or predation. Yellowstone bison also provide a physical link to those ancestors, and show no evidence of interbreeding with domestic cattle. They were declared our national mammal in 2016 because they’re a symbol of wild America, an important part of our heritage, and a key player in an ecosystem that’s much larger than a national park.

We want to send Yellowstone bison to other conservation areas.
Right now, it’s against Montana state law to move wild bison exposed to brucellosis anywhere except to meat processing and research facilities within the state. We’ve started a quarantine program for bison in collaboration with the Assiniboine and Sioux tribes on the Fort Peck Reservation in Montana. From quarantine, animals that repeatedly test negative for brucellosis could be sent alive to other public, private, or tribal lands. Quarantine could reduce the number of bison shipped to slaughter, and facilitate the restoration of plains bison in other suitable areas of the country.

In August 2019, Yellowstone National Park transferred 55 male bison to Fort Peck. While this is a good start, substantial work remains to continue building a sustainable quarantine program. If quarantine is going to succeed, more capacity and partner involvement will be necessary in the future. We want to expand the quarantine program to ensure a more regular and predictable number of bison can move through the protocols. Yellowstone cannot do this alone. Our partners, including IBMP and others, need to play an increased role to make the program sustainable over the long-term.

We need a new bison management plan.
While the existing plan (IBMP 2000) has been effective at preventing brucellosis transmission and maintaining a viable population, we believe that we've outgrown it. New data about bison biology and disease prevalence are available, and public opinion is shifting toward more tolerance for bison in Montana. We need a new paradigm that recognizes bison as wildlife and gives them the ability to move more freely on suitable public lands outside the park.

What You Can Do

We encourage you to learn more about bison conservation. Read about the history of bison management, review some questions & answers, download a copy of Yellowstone Bison: Conserving an American Icon in Modern Society, or watch an extended video Q&A with a lead bison biologist.

Get to know all the people and agencies for whom this issue is important, including state legislators, congressional representatives, and the members of the Interagency Bison Management Plan. We’ll need to work together to find a future that includes wild bison.


Last updated: September 16, 2019

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Yellowstone National Park, WY 82190-0168



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