Management
Who manages Yellowstone bison?
Five federal/state agencies and three tribal entities make decisions about Yellowstone bison in a cooperative effort called the Interagency Bison Management Plan (IBMP). These include the Animal and Plant Health Inspection Service, the Confederated Salish & Kootenai Tribes, the Inter Tribal Buffalo Council, Montana Department of Livestock, Montana Fish, Wildlife & Parks, the National Park Service (Yellowstone National Park), the Nez Perce Tribe, and the US Forest Service (Custer-Gallatin National Forest).
Why are bison killed every winter?
- Bison are killed because they do not have enough room to roam. Yellowstone encompasses a limited amount of habitat and Montana allows very limited numbers of bison in small areas adjacent to the park.
- Allowing the bison population to grow indefinitely could cause overgrazing in some areas and possibly mass starvation of animals in Yellowstone, as well as larger migrations and greater conflict outside the park.
- Yellowstone bison reproduce and survive at relatively high rates compared to many other large, wild, mammal species. The bison population currently increases by 10 to 17% per year.
- Currently, predation by bears and wolves has little effect in reducing the bison numbers. 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 were killed in winter 2019/2020?
A total of 834 bison (17% of the population) were removed during winter 2019-2020, which was within the range of 600 to 900 agreed to by managers. Removals included 548 bison captured at the Stephens Creek facility with 105 entered in brucellosis-quarantine for transfer to the Fort Peck Tribes, 442 sent to slaughter, and one bison dying during handling; 284 bison harvested outside the park in Montana; and two bison shot outside the conservation area.
What is planned for the population in winter 2020/2021?
For the winter of 2020/2021, the NPS recommended removing 500 to 700 bison to slightly reduce the population to 3,850-4,040 at the end of winter and 4,500-4,730 animals after calving. Removals should only occur near the northern park boundary where animals from the central and northern herds intermix. Managers should track migrations and focus removals on the northern herd. If initial removal targets are met, up to 200 additional adult males could be harvested or captured in late winter.
Is Yellowstone’s bison population healthy?
Yes. Yellowstone’s bison population has grown steadily over the last 50 years: from 500 animals in 1970 to more than 4,600 today. Yellowstone bison represent a unique source of genetic diversity. They are one of only a few bison populations with no evidence of interbreeding with cattle.
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 where food is more available (less snow) 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.
Why don't you withdraw from the IBMP?
Yellowstone isn't big enough to manage a migratory species like bison on its own. Bison conservation is a shared responsibility that crosses many political boundaries. Withdrawing from the IBMP would make it more difficult to collaborate with the land management agencies and tribes that share an interest in what happens to bison when they leave the park. Additionally, Yellowstone’s superintendent is not the signatory of the original IBMP. The agreement was signed and approved by the Secretary of the Interior, who would need to make any decision about withdrawing.
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 guided in by riders on horseback. For more information on the capture and shipment process, take a video tour of the Stephens Creek facility or browse photos in our Stephens Creek album on Flickr.
How are bison killed?
We transfer captured bison to tribes who transport them to slaughterhouses for processing.
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. During 2020, we received expert training and worked to improve low-stress handling of bison during handling and 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 or browse photos in our Stephens Creek album on Flickr.
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 4,680 in 2020. 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 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.
