Bison-also commonly known as buffalo-once numbered in the millions on the Great Plains and nearly vanished in the late 1800s. As the continent’s largest land mammal, bison were crucial in shaping the prairie ecosystem. Today the species is listed as “near threatened” and “ecologically extinct,” meaning they no longer play their critical roles in shaping prairie biodiversity.
Although some progress has been made, the bison’s recovery has been slow and is far from complete. Hundreds of thousands of bison remain in North America today, with most being raised for commercial uses in herds on small acreages behind fences. Less than ten percent of existing bison are managed for conservation or as a wild species. Thousands of bison on large landscapes are needed to fulfill their former ecological role. Moreover, most conservation herds are very small, numbering in the dozens to a few hundred, and are mostly confined to small, fenced-in areas. These conditions threaten the genetic health of bison and greatly hinder their ability to roam widely and display natural behaviors. This combination of genetic, ecological, and behavioral concerns makes bison restoration a high priority for wildlife conservation in North America. Keep up to date with bison conservation and recovery at: IUCN Red List.
Ecological Role
While certainly important as species, bison are even more important in returning biodiversity to a landscape that has been missing it for over a hundred years. Bison are a keystone species. This means that bison shape the ecosystem to such a degree that if their presence is lost it would change drastically and have negative impacts on many other species that depended on them and their habits.
For thousands of years bison created a mosaic of habitats and provided influences on the landscape that hundreds of species evolved with and depended on. Grazing, wallowing, trampling decomposition and defecating are just a few. Wallowing is when bison repeatedly roll in dust or mud in selected spots. The resulting shallow depressions, called wallows, collect seeds that were held in the bison fur and may fill with water in the spring and become mini-wetlands with distinctive vegetation. And, because of their large size, bison are an important protein source for scores of carnivores and scavengers, and their decomposing bones and flesh create rich patches of nitrogen and phosphorus for plant growth. Because bison graze in large, dense groups their grazing creates mosaics of different grass heights across the landscape. This heterogeneity is important to many species. For example, the Thick-billed Longspur prefers areas with low vegetation, whereas Sprague’s Pipit and Baird’s sparrow prefer areas with dense vegetation. These and many other interactions between bison and their environment are central to creating the diverse, abundant, and fascinating life of the prairie ecosystem. By reintroducing bison we will certainly start to return many interactions and impacts that have been absent from the landscape for over a century.
This exorbitant ecological role depends on enormous numbers of free-ranging bison. It isn’t likely that the species will return to historic numbers across all of its range, but there is great potential for growth on American Prairie lands and adjacent public lands. Our long-term goal is to grow bison herds to a population size that would result in the species fulfilling their ecological role on the landscape.
Restoration Goals
While certainly crucial in building the prairie, bison restoration is just part of a much broader set of goals to restore the ecosystem. That said, we want to set a high standard for bison conservation in North America. The management of our bison herd should be exemplary for how to restore and conserve the genetic, ecological, and behavioral features of wild bison. In doing so, and by sharing our research and experience, we hope to inspire and support others who wish to restore bison elsewhere in North America, from Canada through the United States to Mexico. Additionally, we want the prairie’s bison herd to be enjoyed by local communities and the public.
We restore bison to their historic habitat on American Prairie lands, providing visitors a chance to experience our national mammal, the majestic species that played a central role in the culture and spirituality of the Indigenous People of the Great Plains and astounded the earliest explorers. Thanks to donors and collaborators, we reintroduced bison on our lands in 2005, returning a species that had been gone from the landscape for more than 120 years.
Currently, bison herd sizes and management are restricted in this region of Montana because of factors like species designation and land use requirements. So rather than focusing on an exact number of animals, it is important to prioritize the ecological role of the species and the impact on the landscape. That being said, we rely on science and research to indicate potential herd sizes that we can use to monitor ecological progress. Preliminary estimates indicate that the 3.2-million-acre (5,000 square miles) American Prairie vision could support tens of thousands of bison. But that number is likely decades away from being possible. So we look to current research, the Vermejo Statement, which estimates that a herd of 5,000 or more will provide an exceptional contribution to bison conservation and ecological recovery.
We believe a herd of 5,000 is realistic and possible. A herd of that size is considered the minimal viable population to fulfill its ecological role on the landscape, to be genetically viable, and to survive what the species encounters on the landscape, including disease, fire and starvation due to drought, and extreme winters.
American Prairie will strive to meet this goal until the species is recovered in the region. We will continue to operate with bison classified as livestock until Montana Fish, Wildlife and Parks and/or the U.S. Fish and Wildlife Service reestablishes bison as a wildlife species managed as a public resource fulfilling its ecological role.
Bison Management
Bison are currently classified as livestock by the Montana Department of Livestock. The American Prairie herd is dispersed across several properties, and graze vast properties enclosed by modified wildlife-friendly fences. We are required by the Bureau of Land Management and State of Montana to pay the same Animal Unit Month (AUM) fees and taxes as any other producer does to graze livestock.
Even though bison are classified as livestock, we follow bison management philosophies that prioritize allowing bison to play their natural ecological role to the extent possible. We use low stress handling techniques when handling bison and handle bison only when necessary.
Genetic Integrity is an important part of bison management. To keep our herds healthy and adaptable we pay careful attention to genetic diversity and cattle gene introgression. Routine DNA testing is conducted on the herd and importing bison with different genetics is done to ensure high integrity and the long term success and survival of our herds. Low genetic diversity can cause abnormalities, low birth rates, and reduced resistance to diseases. Good genetic diversity enables the herd to adapt to changes in their environment. We rely on science to determine where we source bison from and how to manage the genetics of the herd. We also allow for natural selection to take place when breeding. In the simplest terms, this means allowing the weak to die or not breed and the strong to survive and pass on their genes. Bison have adapted and evolved according to the forces of natural selection over thousands of years and we want to ensure that they will continue to do so into the future.
Recent research has concluded that bison experienced multiple hybridization events with cattle over the past 200 years. This research was conducted with DNA samples from the major lineages of bison that survived the severe bottleneck in the 19th century. This means there are likely very few, if any bison that do not have some level of cattle genes in their lineage. Past bison restoration efforts have often been hampered by the thinking that “pure” bison were better. With this new research available it will allow for a more cohesive and inclusive approach to bison restoration. Put simply, A bison that acts like a bison, is a bison and is valuable to species recovery and the ecosystem.
Agriculture, chiefly cattle grazing, is the dominant land use in Montana and in the local areas around American Prairies bison herds. Our bison herds have been successfully coexisting with cattle on these landscapes for decades. Our bison team works closely with neighbors, agencies and stakeholders throughout the region to address concerns that bison may present. Cattle grazing will likely always be the dominant industry in Northeast and North Central Montana and our management aims to show that a thriving bison population can be successfully managed alongside thriving cattle operations.