Are There Any Wild Buffalo Left in America?

Wild bison still roam parts of North America, though their numbers are a fraction of the tens of millions that once blanketed the continent. The most famous wild herd lives in Yellowstone National Park, the only place in the United States where plains bison have existed continuously as wildlife since prehistoric times. But the story of “wild” buffalo in America is more complicated than a simple headcount, touching on genetics, cattle DNA contamination, disease, land politics, and what “wild” even means when nearly every living bison descends from fewer than 100 survivors.

How Close Bison Came to Disappearing

By the mid-nineteenth century, North America held many millions of bison. Within roughly four decades, industrial-scale hide hunting, military campaigns aimed at undermining Indigenous nations, and habitat loss reduced that population to near extinction by the mid-1880s.¹ The slaughter was so thorough that plains bison, the subspecies found across the American grasslands, were saved primarily by five private ranchers who had captured calves and by the survival of a tiny remnant herd in what is now Yellowstone National Park. Every plains bison alive today descends from fewer than 100 founding animals.¹

That bottleneck left a permanent genetic fingerprint. When an entire species funnels through such a tiny number of individuals, the resulting population carries reduced genetic diversity, which can affect disease resistance, reproductive fitness, and long-term adaptability. Understanding that bottleneck is essential to understanding the current state of wild bison, because many of the management headaches and conservation debates today trace directly back to those desperate rescue efforts more than a century ago.

Yellowstone’s Herd, the Only Truly Continuous Wild Population

Yellowstone National Park is home to the only plains bison population that has continually existed as wildlife, on the same landscape, through the near-extinction of the late nineteenth century.² By the early 1900s, however, only 23 wild bison were known to have survived poaching inside the park. To keep the population viable, managers brought in 18 females from Montana and 3 bulls from Texas. Genetic analyses show that the modern Yellowstone herd has merged into one interbreeding population composed of two subunits.²

Today the Yellowstone herd numbers roughly 5,000 animals, though the count fluctuates with seasonal management actions and natural mortality. These bison graze freely across the park’s valleys and plateaus, migrate with the seasons, face predation from wolves and grizzly bears, and breed without human selection. In every meaningful ecological sense, they are wild animals. That distinction matters, because the vast majority of the roughly 500,000 bison in North America live on commercial ranches and are managed as livestock, not wildlife.

Other Free-Roaming Herds in the United States

Yellowstone is not the only place you can find bison living outside fences, though it is the only herd with an unbroken wild lineage. The Department of the Interior manages approximately 11,000 plains bison across 19 herds in 12 states.³ These federally managed herds exist on national wildlife refuges, national grasslands, and other public lands. Some of these herds are fenced and periodically rounded up for health screening or population control, which makes their “wildness” a matter of degree rather than an absolute.

One standout is the Henry Mountains herd in southern Utah. Established in the early 1940s from a small transplanted group, the herd lives on rugged public land with minimal management beyond a hunting season. It has been increasing despite sparse forage and possible competition with domestic cattle, a growth pattern aided by a lack of large predators in the area and a run of wet years.⁴ The Henry Mountains bison are also genetically notable: testing of 129 individuals found no evidence of cattle gene contamination in either the mitochondrial or nuclear DNA, making this one of the genetically “cleanest” bison herds in North America.⁵

Other notable free-ranging or semi-free-ranging herds include those at Wind Cave National Park in South Dakota, the National Bison Range in Montana (now under tribal management), and the Tallgrass Prairie Preserve in Oklahoma. Each of these herds plays a slightly different conservation role, but none shares Yellowstone’s claim of unbroken continuity on the same landscape.

The Cattle DNA Problem

Here is where the question of “wild buffalo” gets uncomfortable. During the late 1800s and early 1900s, several of the private ranchers who saved bison from extinction crossbred them with domestic cattle, hoping to create a hardier range animal. The result is that many bison herds today carry detectable amounts of cattle DNA. A comprehensive genetic study of 11 U.S. federal bison populations found that only one showed cattle contamination in its mitochondrial DNA, but evidence of cattle genes in the nuclear DNA turned up in seven of the eleven herds, about 64 percent.⁶

The amounts are generally small, often just a few percent of the genome, and the animals look and behave like bison. But from a conservation genetics standpoint, even low-level cattle contamination raises questions. Some conservationists argue that only herds with no detectable cattle DNA should be used as source populations for reintroduction efforts. Others counter that the genetic diversity lost by excluding slightly hybridized herds would be worse than tolerating trace cattle ancestry. Herds like Yellowstone’s and the Henry Mountains population, which have tested free of cattle genes, are treated as especially high-value genetic reservoirs precisely because of this debate.

Wood and Plains Bison in Canada

The question of wild buffalo in “America” depends on whether you mean the United States or the continent. Canada’s Wood Buffalo National Park, straddling Alberta and the Northwest Territories, holds one of the largest free-roaming bison populations anywhere. This park was established partly to protect wood bison, a subspecies that is genetically distinct from the plains bison found in the U.S., though the two diverged relatively recently in evolutionary terms.⁷

Wood Buffalo National Park’s bison story has its own complications. In the 1920s, thousands of plains bison were shipped into the park and mixed with the resident wood bison, muddying the genetic picture. Disease also arrived with these transplants. Tuberculosis and brucellosis became established in the herds and remain a management challenge today. Modeling work has shown that the interaction between these diseases and wolf predation can hold bison populations at low density: simulations found a high probability (around 69 percent) that a diseased herd under wolf predation would stabilize at very low numbers, rising to about 94 percent when anthrax outbreaks and drowning were factored in. Without disease, the probability of such low-density persistence dropped below 8 percent.⁸

Despite this, the Wood Buffalo National Park population has been increasing in recent years.⁹ And some smaller herds near the park have surprised researchers. The Ronald Lake and Harper Creek bison populations, which live outside park boundaries, have tested negative for both tuberculosis and brucellosis, and genetic analysis shows they are distinct from the main Wood Buffalo National Park herd despite their geographic proximity.¹⁰ These disease-free, genetically differentiated herds represent an unexpected conservation opportunity.

The Brucellosis Conflict Around Yellowstone

Back in the United States, the biggest ongoing flashpoint in wild bison management is the tension between Yellowstone’s herd and the cattle ranches that surround the park. Bison in Yellowstone carry brucellosis, a bacterial disease that can cause miscarriages in cattle. The livestock industry has spent decades and billions of dollars working to eradicate brucellosis from American cattle herds, and the possibility that wandering bison could reinfect nearby livestock generates intense political pressure.

During winter, Yellowstone bison sometimes migrate to lower elevations outside the park in search of forage, bringing them into potential contact with cattle. Risk modeling shows that the chance of bison-to-cattle transmission is uneven: it is concentrated in local hotspots, varies with climate and bison abundance, and follows a skewed distribution where most areas face very low risk even when a few face elevated danger.¹¹ Still, wildlife-to-livestock brucellosis transmission events have occurred in the Greater Yellowstone Area. After a period from 1990 to 2002 with no known cases, 17 transmission events from wildlife to livestock were investigated over the following decade, though elk were implicated as the primary source in many of those cases.¹²

The management response has been controversial. During harsh winters, bison leaving the park have been hazed back by helicopter, captured and sent to slaughter, or shot. These actions are deeply unpopular with conservation groups and tribal nations, and the debate over how many bison Yellowstone should hold and how far they should be allowed to roam remains politically charged.

What Bison Do for the Landscape

The push to maintain and expand wild bison herds is not purely sentimental. Bison are considered a keystone species of North American grasslands, meaning their behavior shapes the ecosystem in ways that disproportionately affect other species. They graze selectively, creating a mosaic of short-grass patches and taller growth that supports different plant and animal communities. They also wallow, rolling repeatedly in the same spots until they create shallow oval depressions in the soil. These wallows hold rainwater, creating microhabitats for insects, amphibians, and wetland plants that would otherwise have no foothold in upland prairies.¹³

Grassland ecologists increasingly see bison as a tool, or rather a partner, in restoring the health of degraded prairies. Cattle grazing does not replicate the same effects because cattle tend to graze more uniformly and do not wallow with the same intensity. Rewilding advocates argue that returning bison to grasslands they once occupied would benefit not only biodiversity but also soil health and carbon storage, though the scale of land needed for ecologically meaningful herds makes this a long-term vision rather than an imminent reality.¹⁴

Indigenous Nations and Buffalo Restoration

For many Indigenous peoples, the question of wild buffalo in America carries weight that no ecological metric can capture. The deliberate destruction of bison herds in the nineteenth century was inseparable from the campaign to dispossess Native nations of their lands and ways of life. Restoring buffalo is, for many tribal communities, an act of cultural and political resurgence as much as a conservation project. Buffalo are understood not merely as a keystone species with cultural significance but as relatives whose well-being is intertwined with that of the people who depended on them for millennia.¹⁵

Tribal-led bison programs have been growing. The InterTribal Buffalo Council, founded in 1992, now includes more than 80 member tribes collectively managing thousands of bison. Some tribes are working to establish herds on reservation lands where bison can roam with minimal fencing, blurring the line between managed conservation herd and wild population. These efforts have gained momentum in recent years as surplus Yellowstone bison, rather than being sent to slaughter, have been transferred to tribal lands through quarantine programs that screen for brucellosis.

What “Wild” Actually Means for Bison

Defining wildness is the crux of the question. If wild means “never managed by humans, roaming freely without fences, facing natural predation, and breeding without human selection,” then really only the Yellowstone herd fully qualifies in the United States, and even it has been shaped by supplementation with outside animals and by boundary management. Conservation biologists have proposed that the ecological recovery of North American bison will be achieved when multiple large herds move freely across extensive landscapes within all major habitats of their historic range, interacting meaningfully with other native species.¹⁶ By that standard, recovery is still far off.

The roughly 500,000 bison in North America are overwhelmingly commercial livestock, raised for meat on private ranches. The conservation herds, numbering in the low tens of thousands and scattered across public lands, tribal lands, and a handful of private preserves, represent the pool from which any future wild population would have to be drawn. The tension between treating bison as livestock and treating them as wildlife plays out in everything from grazing permits to genetic management to the legal authority different agencies have over the animals.

Climate, Movement, and the Future

One emerging concern is how climate change will affect the bison that are left. Research tracking bison movement patterns found that air temperature was the strongest single predictor of how far the animals moved in a day, with movement rates dropping by about 48 percent when temperatures exceeded 28°C (roughly 82°F). Severe drought, measured by deep soil moisture, also reduced movement more than moderate dry spells did.¹⁷ Bison that move less forage less effectively and exert less of the landscape-shaping influence that makes them ecologically valuable. As heat waves and droughts become more frequent across the Great Plains, the functional wildness of bison herds could erode even where the animals are technically free-ranging.

This connects back to the land question. Bison historically adapted to climate variability by migrating vast distances, following seasonal green-up across the plains. Today’s wild herds are confined to relatively small patches of habitat. A bison herd that cannot move in response to drought or heat has fewer options than its ancestors did, and its ecological footprint shrinks accordingly. Proposals for landscape-scale connectivity, corridors linking isolated herds and allowing seasonal migration, remain mostly conceptual but are gaining traction in conservation planning discussions.

Staying Safe Around Wild Bison

If you visit Yellowstone or another park with free-roaming bison, the animals deserve a wide berth. A study of bison-related injuries at Yellowstone between 2000 and 2015 found that 80 percent of the people hurt had actively approached bison before the incident, and the average distance from person to bison before injury was only about 3.4 meters, roughly the length of a car. Nearly half of the injured visitors were photographing the animals at the time, and 60 percent were hurt when groups of three or more people approached together, a dynamic where social pressure seems to override individual caution.¹⁸ Bison can sprint at speeds around 55 km/h and weigh up to 900 kg. Park guidelines recommend staying at least 25 yards (about 23 meters) away, but the injury data suggest many visitors do not take that seriously until it is too late.

The fact that bison injuries keep happening underscores a broader point about the animals’ status. These are not tame cattle standing in a field. The bison you see in Yellowstone or the Henry Mountains are wild animals with the speed, mass, and temperament to prove it. Their survival, against extraordinary odds, is one of the more remarkable conservation stories on the continent, even if the word “wild” comes with more asterisks than most people expect.