Bison Management

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2 minutes, 6 seconds

The protection and recovery of bison in Yellowstone is one of the great triumphs of American conservation. This video explains why Yellowstone bison are managed.

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The National Park Service (NPS) has sole authority to manage bison within the boundaries of Yellowstone National Park. However, the NPS coordinates with other federal, state, and American Indian Tribes pursuant to an Interagency Bison Management Plan (IBMP) signed in 2000 by the secretaries of Agriculture and Interior and the governor of Montana because bison, like other wildlife, leave the boundary of the park. Bison are managed differently than other wildlife because the state of Montana provides limited tolerance for bison migrating out of the park.

In 2024, the NPS created a new bison management plan through a Final Environmental Impact Statement and Record of Decision pursuant to the National Environmental Policy Act because of new scientific information, changed circumstances, and litigation. The 2024 plan defines how the NPS will manage bison within the park. It also sets conditions for how the NPS will support its partners in their efforts outside the park. The NPS will continue to meet with the other federal, state, and American Indian Tribes under the existing framework for the IBMP to coordinate the implementation of the park’s bison management plan and to meet the principal purpose identified in the 2000 IBMP.


Our Goals

We preserve a sustainable population of 3,500-6,000 wild, migratory bison.

Yellowstone’s bison are the closest resemblance left today of the vast herds that once roamed the continent. Bison act as ecosystem engineers fundamentally designing grassland ecosystems, and they hold significant cultural importance to people, with a connection spanning thousands of years.

We coordinate with federal, state, and Tribal partners to manage the bison population.

Yellowstone bison must be managed because the population is growing exponentially and there is limited winter range for bison within the park. Like other wildlife, bison migrate out of the park to find food in winter, but unlike other wildlife, there is limited tolerance for them outside the park. Yellowstone works with its partners to control numbers, limit bison migrating out of the park, and help Tribes restore Yellowstone bison to their livelihoods.

We develop the best available science to preserve our national mammal.

Making decisions about bison population management requires contemporary research on population viability, habitat use, and the effects that bison have on grasslands to ensure a sustainable bison population and habitat.


Conserving Yellowstone Bison

Archeological evidence indicates bison have lived in the Greater Yellowstone Area for more than 10,000 years. By 1902, only 23 bison were counted in the park, the last wild bison remaining in North America. Concerted conservation efforts through the 1900s recovered Yellowstone bison as the most valuable conservation population of bison in the world.

As the population recovered, bison began migrating out of the park into Montana. The movement of bison from the park into the adjoining state of Montana created one of the most complex wildlife management dilemmas of the present day.

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34 minutes, 49 seconds

Bison Program Coordinator Chris Geremia talks about the past, present, and future of bison management in Yellowstone National Park.

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NPS Bison Management Plan

Multiple federal, state, and Tribal entities are involved in managing bison and hold different opinions on how they should be managed. These opinions are heightened because each entity has varying authorities over bison management depending on the land the bison are on, whether it be the national park, surrounding U.S. Forest Service lands, or private lands in Montana.

In 2024, the NPS created a new Bison Management Plan to address how we manage bison in the park and support our partners with their actions outside the park. This plan builds a better future for our national mammal by revising the tools used for controlling numbers, setting a target population range, and determining how we manage brucellosis in the population. The 2024 plan identifies three ways to control bison numbers: the Bison Conservation Transfer Program (BCTP), the Tribal Food Transfer Program (TFTP), and Tribal harvests and state hunts.

bison in a holding pen near snowy mountains
Bison in holding pens to prepare for transfer to Fort Peck Indian Reservation.

Bison Conservation Transfer Program (BCTP)

The 2024 plan prioritizes the BCTP to capture and identify bison that do not have brucellosis and transfer them to Tribes. As bison migrate north out of the park, some are captured at Yellowstone’s bison facility and entered in the program. The goal is to enter 100-300 animals each year; however, if a lower number of bison migrate out of the park, or the population is below 3,000, we may not reach this goal during some years. Roughly 30–40% of the captured bison qualify for the program because animals must test negative for brucellosis and be younger than 3 years of age.

Once in the program, animals are moved between facilities to undergo various testing phases. The first phase is completed in Yellowstone quarantine facilities or on private lands leased by Animal and Plant Health Inspection Service (APHIS) near the northern park boundary. APHIS and Montana animal health officials certify bison as brucellosis-free at the completion of this phase, which takes approximately 300 days for males and 2.5 years for females. The bison are then moved to the Assiniboine and Sioux Tribes of the Fort Peck Indian Reservation, where the bison are held in an assurance testing facility for one additional year of testing. Afterward, the Fort Peck Tribes transfer some bison to the InterTribal Buffalo Council, who distribute them to other Tribes across North America.

Listen to the story of the first live bison transfer in 2019 to the Fort Peck Indian Reservation located in northeastern Montana (this episode was created before the expansion of the park’s bison facility and the reduction of timelines for male bison in the BCTP):

A bison leaping out of a trailer
Yellowstone bison released at Fort Peck Indian Reservation in 2019.

Tribal Food Transfer Program (TFTP)

Yellowstone transfers bison to Tribes who then sacrifice them for their meat and hides at meat-processing facilities. The program supports Tribal food independence and provides bison as food to Tribal members who may not be able to participate in harvests outside the park.

Tribal Harvests & State Hunts

Currently, eight American Indian Tribes exercise their treaty rights to harvest bison outside the park. These harvests are managed by each individual Tribe. We support Tribal efforts to increase harvest outside the park to provide them with access to traditional food and cultural and material sources.

The state of Montana also manages a relatively small public hunt. Combined, these efforts can be an effective tool to manage bison numbers when weather conditions are favorable.

a herd of bison moving through a field at sunrise
A bison group on the move in Lamar Valley at sunrise.

Target Population Range & Adaptive Management

Managing wildlife populations to a static number is not realistic or appropriate. Bison migrate with the weather, causing the number exiting the park to vary substantially each year. Therefore, the target bison population under the 2024 plan is between 3,500 and 6,000 animals.

Each year’s management strategy adapts to that year’s bison population and migration numbers. There is no set removal target each winter, but we provide guidelines to our IBMP partners and Tribes each fall to avoid removing so many bison in a single year that it affects the health of the population.

Below a population of 5,200, we only place bison in the BCTP and utilize the TFTP to remove brucellosis-positive bison that are identified in selecting animals for the program. Above 5,200, we rely primarily on Tribal harvests and state hunts to manage numbers. If harvests and hunts are unable to reduce numbers, we commit to decreasing the population by removing additional animals through the TFTP. We prioritize the removal of brucellosis-infected bison, which stabilizes or decreases brucellosis prevalence over time. If the late-winter population nears 3,000 animals, the park protects the population inside the park and encourages partners to reduce hunting outside the park.


Studying Yellowstone Bison

Each summer, bison managers conduct aerial counts of the bison population using fixed-wing aircraft. We integrate these counts with survival rates of radio-collared bison and ground surveys of male-to-female and female-to-calf ratios to estimate the population status. We then use population modeling techniques to provide management recommendations to our partners for implementing hunts in winter.

Genetic Monitoring

Bison in the park are a metapopulation or a single population with two distinct breeding groups. During the July and August breeding season, we collect genetic samples from bison using biopsy dart projectiles. From these samples, we determine gene frequencies and track genetic diversity to help ensure that we are sustaining the population.

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1 minute, 12 seconds

A Yellowstone field crew collects bison DNA samples during the rut.


Rangeland Monitoring & Grazing Experiments

Bison use only about 40% of the grazeable acreage in the park, but in some areas, like Lamar Valley, they graze intensively. We use small grazing exclosures throughout the high-grazing areas of the park to evaluate consumption patterns and impacts on soil health, plant productivity, and nutrient cycling. We monitor long-term exclosures to see how plant communities are changing with and without bison.

To view more bison research in Yellowstone, visit Science Publications and Reports.


Questions & Answers


Interagency Bison Management Plan (IBMP)


NPS Bison Management Plan


Bison Stats




More Information

a bison calf nursing during an early morning
History of Bison Management

Learn about the history of bison management in Yellowstone.

A bull bison grazing in tall grass on the Blacktail Deer Plateau.
Bison Ecology

Learn more about North America's largest land-dwelling mammal.

two park rangers inspecting the wing of a small bird
Science Publications & Reports

View science publications and reports created by Yellowstone's Center for Resources on a variety of park topics.

two park rangers walking with bison seen in the background

Learn about the current natural and cultural resource issues that Yellowstone is managing for this and future generations.


Bison Management News

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    Last updated: July 24, 2024

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