FAQs Bison Management

Rick Wallen

Video Q&A - Bison
In a videotaped interview, Rick Wallen answers a range of questions about the challenges of bison conservation and the park's management goals.


What is the current bison population?

  • In August 2016, the bison population was estimated to be near 5,500, roughly an 11% increase over 2015.
  • In 2000, the Secretaries of Agriculture and Interior and the Governor of Montana signed a court-mediated agreement that included guidelines to limit bison abundance near 3,000.
  • Biologists from the National Park Service (NPS) have proposed removing 600 to 900 bison near the northern boundary this winter to offset the population increase expected this year.

Why are bison being removed from the population?

  • Bison populations increase rapidly when environmental conditions are suitable. Yellowstone bison are prolific and have high survival rates, with wolves currently killing few bison because elk are more vulnerable prey. We're not aware of any bison conservation herds in North America that are naturally regulated: all require population reduction through hunting or culling.
  • Bison need to be removed from the population at times. The fast-growing bison population could fill available habitat and out-pace the acquisition of additional habitat and tolerance for bison in Montana. Options for relocating Yellowstone bison elsewhere are limited by real and perceived disease and social concerns.
  • Under-nutrition (starvation) only contributes to high mortality when bison abundance is high and snow pack is at or above average. Also, most bison migrate to lower elevation areas in response to such severe weather events —which eventually brings them into conflict with agriculture and development.
  • The food-limited carrying capacity inside the park could be as high as 5,500 to 7,500 bison during winter, but lower-elevation habitat for bison is limited by mountains in the park and by competition with agriculture, development, and transportation systems outside the park.
  • A panel of expert scientists reviewing Yellowstone bison and brucellosis issues concluded that culling or removals of bison, along with hunting, would be necessary to limit the size of the bison population for biological, social, and political reasons.

How will the bison be removed from the population?

  • Members of the Interagency Bison Management Plan (IBMP) agreed to use public and tribal hunting outside the park as the primary method for removing bison from the population. However, logistical and social challenges generally limit the effectiveness of hunting to a maximum of several hundred bison annually. Congress has specifically prohibited hunting within Yellowstone National Park.
  • The secondary method of population reduction will be capturing bison near the park boundary and then transferring them to Native American tribes for processing and distribution of meat and hides to their members. Under this year's IBMP operations plan, capture will begin no earlier than February 15, 2016 and will cease no later than March 31, 2016. Capture is done without regard for age, sex, or disease status.

Why are bison being shipped to meat processing facilities?

  • The demand for bison for quarantine or research is minimal due to a lack of facilities, and the social capacity for public and treaty harvests near the park boundary is probably only about 300 to 400 bison each year due to the timing of migration, constricted area where bison are currently hunted, and the number of different management jurisdictions that authorize hunting of Yellowstone bison (4 tribes and the State of Montana). Thus, bison at times need to be removed from the population by other means, such as shipments to meat processing facilities, even though there is little political or social support for such actions.
  • At the current population level, there could be a mass migration of many hundreds of bison out of the park this winter if there is deep snow pack at higher elevations. Also, without harvests or culls, we predict the population will increase to nearly 6,000 bison by the end of winter in 2016.

Why can't you harvest bison through hunting instead of shipping them to meat processing facilities?

  • Hunting in the park is not authorized by Congress and longstanding policy prohibits hunting in units of the NPS system unless specifically authorized by Congress (NPS Organic Act of 1916, 16 USC I, V § 26).
  • Even if hunting were to be authorized, it may not be popular with the vast majority of the American and world-wide public due to wounding, behavioral changes (avoidance) and other unintended effects to bison and other iconic and threatened wildlife species (e.g., bears, elk, pronghorn, wolves), and adverse effects to wildlife viewing and visitor enjoyment.
  • Hunting outside Yellowstone's park boundaries in Montana generally removes less than 300 bison each winter due to variable and often infrequent migration of bison outside the park until late winter when females are late in pregnancy and hunting of these females is considered undesirable. Also, there appears to be a social tolerance that will limit substantial increases in bison hunting and associated gut piles in places near the park boundary.
  • In 2013, a panel of expert scientists reviewing bison and brucellosis issues concluded that culling or removals of bison, along with hunting, would be necessary to limit the size of the bison population.

Why don't you just keep all the bison within Yellowstone National Park?

  • While the park provides a large amount of habitat for bison, it does not provide sufficient habitat for the population during some winters when deep snow limits access to forage at higher elevations. As a result, some bison migrate to low elevation habitat outside of the park in search of food.
  • Annual migration allows bison to access necessary resources for their survival—similar to bighorn sheep, deer, elk, moose, and pronghorn in the system. If migration by Yellowstone bison into Montana is restricted or shortened by human intervention, then bison numbers will be largely determined by food availability inside Yellowstone, with substantial winter mortality occurring after bison reach high densities.
  • Fortified fences could be used to limit bison migrations, but they would also impede or serve as a barrier to the movements of other wildlife species such as bighorn sheep, deer, elk, moose, and pronghorn. Fencing creates a zoo-like atmosphere and is generally inconsistent with wildlife management principles for the State of Montana and the NPS.
  • The distribution of hay or commercially prepared rations at locations near the boundary of Yellowstone National Park during winter could conceivably encourage bison to terminate their migration and remain in the park. However, bison and other ungulates would become increasingly reliant on these provisions while continuing to feed on vegetation in the vicinity and degrading surrounding habitats. These outcomes are contrary to the conservation of a wild bison population and NPS policies for managing biological resources. Most natural resource managers attempt to avoid the supplemental feeding of wildlife.

Are the bison leaving Yellowstone National Park because it is overgrazed?

  • To date, the central and northern bison herds have not reached the estimated food-limited carrying capacity of approximately 5,500 to 7,500 bison inside the park. Also, several assessments of conditions by scientists and land managers have indicated the park is not overgrazed.
  • National Park Service biologists have recommended maintaining a bison population that fluctuates between 2,500 and 4,500 to preserve ecological processes that meet conservation needs and to mitigate social and political conflicts in Montana.

Why don't you just let the bison roam freely outside Yellowstone National Park?

  • The State of Montana allows some bison to migrate outside Yellowstone National Park and occupy suitable winter range near the park boundary—and tolerance on additional range may occur in the future. However, mass migrations of many hundreds of bison out of the park have, at times, upset state and local governments and many private landowners and cattle operators.
  • If bison were allowed to increase in abundance and disperse unimpeded into cattle-occupied areas of Montana, it is likely those bison would be lethally removed by state employees or during regulated hunts. Also, the state may retract tolerance for bison in Montana in some areas because the agriculture department has superseding management authority due to chronic brucellosis infection in Yellowstone bison.
  • Thus, management practices such as hunting, hazing, capture, and culling are necessary at times to limit the abundance and distribution of bison and allow people (including federal and state managers) time to learn to live with, and manage, bison.

Why don't you allow native predators to control bison numbers?

  • Yellowstone National Park supports an abundant and diverse association of large predators, including black bears, coyotes, grizzly bears, mountain lions, and wolves. These predators occasionally kill bison, but primarily feed on elk even though winter abundance in Yellowstone has decreased about 75% since wolves were restored in 1995. As a result, predation has had a minor influence on bison population dynamics.
  • Bison are massive and often defend against wolves as a group, which makes them more difficult to attack than smaller elk that often run when attacked. As a result, wolves in Yellowstone National Park prefer elk and only tend to kill significant numbers of bison during winters with deep and prolonged snow pack that make malnourished animals more abundant and susceptible. Thus, it is unlikely predators will begin to regulate bison numbers to much lower densities in the near future.

Why can't you ship bison to other areas or quarantine facilities rather than meat processing facilities?

  • There are no operational quarantine facilities, which are fenced areas where bison are repeatedly tested over several years to ensure they are free of brucellosis. Also, there are no approved terminal pastures, which are fenced areas within which bison would be harvested over time.
  • The NPS is working with American Indian tribes, the Bureau of Indian Affairs, and other federal and state agencies to evaluate alternatives for a quarantine program.The NPS expects to release an Environmental Assessment for public comment in 2015.
  • Substantial funding would be needed to establish and operate a quarantine facility and associated terminal pasture.
  • It has been difficult to relocate brucellosis-free Yellowstone bison due to misperceptions and stigmas regarding disease status and other factors.

What happens to all the meat, hides, horns, etc. from bison shipped to meat processing facilities?

  • The NPS has proposed to periodically provide some Yellowstone bison to American Indian tribes and tribal organizations like the InterTribal Buffalo Council, for direct transfer to approved meat processing facilities.
  • The distribution of meat, hides, horns, and other bison parts will be at the discretion of the American Indian tribes and tribal organizations to support their nutrition and culture.

Why are bison managed differently from other wildlife and not allowed to move freely into Montana and disperse to new areas?

  • Yellowstone bison are managed differently than other wildlife that migrate or disperse outside the park because the Secretaries of Agriculture and Interior and the Governor of Montana signed a court-mediated agreement in 2000 that provided guidelines for limiting bison abundance and distribution in Montana.
  • Yellowstone bison have been chronically exposed to the non-native disease brucellosis that can be transmitted to cattle and cause them to abort calves. As a result, bison are not allowed to move unimpeded into cattle-occupied areas in Montana.

Are removals of bison and shipments to meat processing facilities precedent setting for national parks?

  • The use of removals to manage wildlife and their habitats is not a new practice in NPS units.
  • During 1908 to 1968, personnel relocated about 810 bison from Yellowstone National Park to other areas and shipped about 4,200 bison to meat processing facilities. Since 1968, an additional 7,980 bison have been culled from the population.
  • From 1930 through 1968, natural resource managers from Yellowstone National Park and the State of Montana relocated about 13,500 elk, shot or trapped about 13,000 elk, and permitted hunters to harvest another 45,000 elk north of the park.
  • Bison are also periodically captured and removed from populations in Wind Cave, Badlands, and Theodore Roosevelt national parks, as well as the Tallgrass Prairie National Preserve. Many of these bison are provided to American Indian tribes to support their nutrition and culture.

What are the economic costs of bison removals from Yellowstone National Park?

  • The NPS is currently expending about $1.2 million per year to implement the IBMP.
  • The overall costs of shipping bison to meat processing facilities and distributing the meat could be between $50,000 and $100,000.

Has the Interagency Bison Management Plan (IBMP) been successful at accomplishing its goals?

  • Yes, since the Record of Decision for the IBMP was signed in December of 2000, the average annual abundance of Yellowstone bison has been about 3,940. The State of Montana has enhanced the conservation of bison by enlarging the area where they are tolerated north and west of Yellowstone National Park during winter and spring.
  • In addition, there have been no incidents of Yellowstone bison infecting cattle with brucellosis, while more than 20 incidents of elk infecting cattle have occurred in the greater Yellowstone area since 2002.

Contact the Park

Mailing Address:

P.O. Box 168
Yellowstone National Park, WY 82190-0168


(307) 344-7381
Recorded information. For road and weather information, please dial 307-344-2117.

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