The conservation of bison in North America is a continuing effort to help American bison (Bison bison) recover from near extinction. Plains bison, a type of bison (Bison bison bison), are important for the health of the North American Great Plains. Bison are a species that needs special care because their numbers dropped very low at the end of the 19th century. The near extinction of bison during the 19th century disrupted important connections between bison, grassland ecosystems, and the cultures and lives of Indigenous peoples. English speakers called this animal "buffalo" when they first arrived. The scientific name "bison" was used to clearly separate this animal from true buffalo. The word "buffalo" is still often used because it holds cultural meaning, especially for Indigenous people.

Recovery started in the late 19th century when a few people saved the last remaining bison, and the government worked to protect the small group of bison in Yellowstone National Park. In the 20th century, focused efforts helped increase bison numbers, though they still live mainly in small, separate groups today. Scientists continue to learn more about how to manage and protect bison. Today, efforts to help bison include protecting their original genetic traits and reducing mixing with cattle genes.

Context

Bison once lived across most of North America in very large numbers, with tens of millions of them. Before the 19th century, bison were a key part of the shortgrass prairie habitat. Their grazing habits changed the food web and landscapes in ways that helped many different plants and animals live together. Large areas of grass supported the movement of about 30 to 60 million American bison, which lived across much of North America. These animals lived from the eastern seaboard states to parts of Washington, Oregon, and California, but the largest groups were in the "great bison belt" on the shortgrass plains east of the Rocky Mountains, stretching from Alberta to Texas.

The grasslands once had more than 1,500 plant species, 350 bird species, 220 butterfly species, and 90 mammal species. Bison lived alongside elk, deer, pronghorn, swift fox, black-footed ferrets, black-tailed prairie dogs, white-tailed jackrabbits, bears, wolves, coyotes, and cougars. Bison used their horns to scratch trees, which helped keep trees from growing too tall and taking over the grasslands. As bison ate grass, they spread seeds by passing them in their waste. The varied landscape created by bison helped birds that travel long distances each year. For example, long-billed curlews need areas with short grass, long grass, and mud on the prairie to raise their young. Mountain plovers use bison wallows, or muddy areas, as places to nest. Prairie dogs benefited from bison eating grass near their homes. Bison also enjoyed the regrowth of plants that prairie dogs had eaten, which made the grass shorter and easier to see predators. Many animals, including bald eagles, ravens, black-billed magpies, swift foxes, golden eagles, grizzly bears, wolves, beetles, and nematodes, relied on bison carcasses for food.

Bison were very important to Native American cultures for thousands of years, providing food, clothing, shelter, and tools. In the 19th century, bison became a main food source for early explorers, fur traders, and European settlers. When European Americans moved west and brought horses, the bison population started to decrease. As conflicts with settlers grew, the U.S. Army began efforts to move Native American tribes to lands set aside for them. Killing bison helped the government try to make Native Americans become farmers. Top military leaders, politicians, and President Ulysses S. Grant believed that destroying bison would help remove Native Americans from their lands. Hundreds of thousands of bison were killed by U.S. soldiers and hunters. The transcontinental railroad made it easier to hunt bison on a large scale, and the invention of the repeating rifle increased the speed of hunting. The development of a tanning method that made bison hides into strong, valuable leather also led to more bison being killed for trade.

Early efforts

In the late 1860s, private citizens started capturing and sheltering bison. In 1874, both houses of Congress passed a law called H.R. 921 to stop the killing of bison in the United States. However, President Ulysses S. Grant did not sign the bill, so it did not become law. By the late 1880s, large groups of bison that once lived across the land were nearly gone. As their numbers dropped very low, bison became a species that needed protection. People began working to save them by keeping them safe and caring for them. The near loss of bison disrupted important connections between bison, grasslands, and the cultures of Plains Indians. When hunting stopped and private citizens provided land for bison to live, their numbers began to grow again. Some ranchers tried to breed bison with cattle, but these experiments failed and were not repeated. Most bison used to create conservation herds came from private herds, so some of today’s bison have genes from cattle. Bison were almost completely gone from their original areas, which hurt the diversity of grassland ecosystems.

Oral stories from the Confederated Salish and Kootenai tribes tell of a man from the Pend d’Oreille tribe named Atatice, who realized something needed to be done as bison disappeared. Atatice’s son, Latati, or Little Peregrine Falcon, led six orphaned bison west to the Flathead Reservation. His stepfather, Samuel Walking Coyote, sold them to horse traders Michel Pablo and Charles Allard in 1884. The Pablo-Allard herd grew until 1896, when Allard died and his share of the herd was sold to ranchers. Pablo’s herd continued to grow and roam freely along the Flathead River. By the early 1900s, the Pablo-Allard herd was considered the largest group of bison left in the United States. In 1904, Pablo learned the government planned to sell parts of the Flathead Reservation for settlement. After failed talks with the government, Pablo sold the herd to the Canadian government in 1907. The transfer took until 1912, as bison were captured and sent by train from Ravalli, Montana, to Elk Island to create a conservation herd.

Yellowstone National Park was created on March 1, 1872. Even though soldiers from the First U.S. Cavalry were stationed at Fort Yellowstone to help protect wildlife, people still hunted bison illegally. By the 1890s, only about two dozen bison remained, spending winters in Pelican Valley. In May 1894, Congress passed the Lacey Act of 1894, a law that punished people who hunted animals illegally on public lands. This law helped Yellowstone managers begin to recover the bison population. In 1902, Yellowstone officials bought 21 bison from private owners and raised them at Mammoth and then at the Lamar Buffalo Ranch. This increased the genetic diversity of the Yellowstone herd but also likely introduced cattle genes into the population.

Some bison lived on the National Mall near the Smithsonian Castle from 1888 until they were moved to the National Zoological Park, which opened in 1891. Taxidermist William Temple Hornaday brought them to the Smithsonian in 1886 to collect specimens. When he saw how close bison were to extinction, he changed his mission from hunting them for display to helping protect them in the wild. The American Bison Society (ABS) was formed in 1905 with Hornaday as its president to support bison recovery. President Theodore Roosevelt, who was named honorary president of the society, used his position to help the New York Zoological Society and the ABS secure land, buy bison from ranchers, and promote bison reintroduction projects. One of the first projects supported by Roosevelt and the ABS was the National Bison Range, which brought some of the Allard herd back to the Flathead Valley. Other projects included the Wichita Mountains Reserve and Wind Cave National Park. On October 11, 1907, six male and nine female bison were sent by train from the New York Zoological Park to the Wichita National Forest and Game Preserve in Oklahoma. Comanche Chief Quanah Parker arrived at the train station in Cache, where the bison were transferred to wagons and taken 13 miles to the preserve. Many Comanche children had never seen a bison before. In 1913, the ABS sent 14 bison from the New York Zoological Gardens to Wind Cave National Park, which was created in 1903 by Roosevelt. Six more bison were sent to the park in 1916 from Yellowstone. Congress also created public bison herds at Sully's Hill National Game Preserve and Fort Niobrara National Wildlife Refuge.

The bison at the Lamar Buffalo Ranch eventually mixed with the free-roaming bison in Yellowstone Park. By 1954, their numbers had grown to about 1,300 animals. Bison reproduce and survive at high rates compared to many other large wild mammals, so Yellowstone managers limited their growth by removing some animals regularly. A ban on culling, which started in 1969, caused the bison population to grow quickly. Removals began again in 1991 and averaged 233 bison per year from 1991 through 2017 as officials tried to control the population’s rapid growth of 10 to 17 percent each year. Guidelines were set each year on how many bison should be removed. Many of the slaughtered bison were given to Native American tribes, relief agencies, and sold. Some live bison were sent to zoos, reservations, and other parks. In recent years, hunting limits for bison leaving Yellowstone have also been increased in Montana and Wyoming.

Contemporary approach

Preserving the wild nature of bison is very important for their conservation and helps manage conservation herds. This includes keeping a mix of different ages and genders and letting bison live naturally with their environment. Most conservation herds are small and separated from other groups. Larger herds in big areas where natural challenges like food shortages or predators exist, with little human involvement, are considered the best way to help bison thrive. Natural selection happens when bison face challenges like predators, harsh weather, or competition for food and mates. The current plan requires at least 1,000 bison in a herd. Scientists are still learning more about bison behavior and how to manage them.

A team effort has created bison herds that focus on keeping their original genes and avoiding mixing with cattle. These herds are managed by tribes, government groups, and other organizations to protect wild bison and their genetic variety. Breeding programs and genetic tests help reduce the chance of bison mixing with cattle. Studies show most bison herds have some cattle genes. While mitochondrial DNA might affect cell function, most traits are controlled by chromosomal DNA, which holds most of an organism’s genetic information. The small amount of mitochondrial and chromosomal DNA from cattle may not greatly affect how bison reproduce or look. Herds with diverse genes are important for saving the species. Brucellosis was found in Yellowstone bison in 1917, after it was discovered in cattle in the U.S. in 1910. The disease spread to wild elk and bison from European cattle. Controlling the disease is a challenge for bison recovery. Other challenges include bison moving long distances and legal disagreements over land management.

Conservation biology focuses on restoring natural processes that benefit ecosystems, not just bison as individuals. Bison grazing helps soil health, plant growth, and balance in ecosystems. Prairie environments were shaped by natural wildfires and bison grazing, a process called pyric herbivory.

US Department of the Interior Bison Conservation Initiative

The U.S. Department of the Interior (DOI) is the main agency in the United States that protects public lands and natural and cultural resources. It manages about one-third of North America’s bison in conservation herds. The National Park Service (NPS), U.S. Fish and Wildlife Service (USFWS), and Bureau of Land Management (BLM) manage about 11,000 bison in 19 herds across 12 states. These agencies work with the Bureau of Indian Affairs and U.S. Geological Survey to help protect bison. In 2008, the Bison Conservation Initiative (BCI) was created, forming the Bison Working Group (BWG), a team from different agencies that includes the NPS, USFWS, BLM, Bureau of Indian Affairs, and U.S. Geological Survey. The BCI was updated in May 2020. The BWG helps protect bison by using practices that keep bison wild, reduce artificial selection, and allow natural selection, such as competition for breeding. A metapopulation strategy helps keep genetic diversity and health by using science-based methods to connect bison herds across DOI lands. The DOI works with partners, including states, tribes, nations, and organizations, to manage large bison herds on suitable lands.

The National Park Service manages three free-ranging bison herds in Grand Canyon, Grand Tetons, and Yellowstone National Parks. Yellowstone is the only place in the United States where bison have lived without interruption since ancient times. The Grand Tetons and Yellowstone herds have little mixing with cattle genes but are not disease-free. The Grand Canyon herd has no disease but has some cattle gene mixing.

Many bison herds managed by the Interior Department are small and enclosed by fences. These herds have only small traces of cattle gene mixing. Herds with fewer than 400 bison face problems like inbreeding and genetic drift, which reduce their ability to adapt to the environment. A 2019 study by the National Park Service found that limited movement between herds contributes to these issues.

Bison herds grow quickly, often faster than the land can support. Capture is sometimes needed to control herd size and to donate bison to help other conservation efforts. Low-stress handling methods during capture reduce stress for bison and workers while supporting the goal of managing bison as wildlife. The BWG also manages diseases in bison that could harm livestock or other herds.

Wind Cave National Park added 20 bison between 1913 and 1916 and keeps their numbers around 425 through culling. Theodore Roosevelt National Park added 29 bison to its South Unit in 1956 and moved 20 to its North Unit in 1962. These herds are kept at about 350 and 20 animals, respectively, through culling. Badlands National Park added 53 bison between 1963 and 1964, and another 20 in 1984. Their herd is kept around 700 animals through culling.

Greater Yellowstone Ecosystem

The management of the Yellowstone National Park bison herd changed during the second half of the 20th century. Instead of using care methods that controlled bison, officials focused on helping bison behave naturally and move freely within the park. Before 1975, few male bison left Yellowstone, but as their numbers grew, groups began migrating across the park’s northern and western borders to find more space for winter grazing and to explore new areas in the Greater Yellowstone Ecosystem. Park and state officials worked hard to stop bison from mixing with cattle. Brucellosis, a disease that affects elk and bison in Yellowstone, is a concern because ranchers fear it might cause Montana to lose its status as brucellosis-free. Montana law allows wild bison exposed to brucellosis to be moved only to meat processing or research facilities within the state. Some bison were captured and sent to slaughter, while others were shot by hunters or officials. Montana held a licensed hunt for bison that left the park from 1985 to 1991, but the number of bison migrating outside the park kept rising. This led the National Park Service to create plans to manage bison near the park’s edges. Disagreements grew between environmental groups, ranchers, and government officials.

During harsh winters, bison used areas managed by the U.S. Forest Service for grazing, which were also used by cattle in the summer. In 1995, Montana’s legislature declared Yellowstone bison needed special disease management and sued the National Park Service for letting bison leave the park. After five years of legal disputes and discussions, Montana and the federal government created the Interagency Bison Management Plan (IBMP) to guide bison management around Yellowstone. This plan involves five agencies and three tribal groups working to keep bison wild and reduce the risk of brucellosis spreading to cattle. Since the IBMP began, the bison population has ranged between 2,400 and 5,500 animals. No cases of brucellosis have been found in cattle from bison, partly because agencies keep bison and cattle separated. Montana now allows bison to live in some areas near the park that were once off-limits, including some places year-round, which is a major step for conservation. However, most areas outside Yellowstone still do not allow wild bison, limiting their recovery. Much of their historic winter habitat is no longer available due to human development, and only small numbers of bison are allowed near the park. Hunting is not allowed inside the park but happens in areas outside the northern boundary near Gardiner, as decided by the state. Each year, the number of bison to be removed is set, with tribal and state hunters allowed to take a specific number. Montana issues hunting permits, and four tribes have the right to hunt Yellowstone bison based on long-standing agreements. Most bison removed are sent to slaughter, and the meat is shared with participating tribes. The IBMP also allows bison to join the Bison Conservation Transfer Program when space is available.

Bison Conservation Transfer Program

Yellowstone bison are special because they make up the largest group of bison living on public land in the United States. Creating a quarantine program that followed Montana state laws was important to move bison from Yellowstone to other groups that protect wildlife. People discussed quarantine during the 1990s when planning the IBMP. Between 2005 and 2012, the Animal and Plant Health Inspection Service (APHIS) created and tested methods to find Yellowstone bison that do not have brucellosis. Quarantine worked because bison that tested negative for the disease stayed healthy and could be declared free of brucellosis. The original plan was to move bison that finished the pilot program to public or tribal lands, but Montana was not ready to approve any locations in 2010. Turner Enterprises Inc. cared for the bison and their young for five years on a 12,000-acre fenced area of the Flying D Ranch. Tribal and state leaders signed an agreement in 2012 to transfer bison that were part of the 2005–2012 pilot study. In March, 63 bison from Yellowstone quarantine areas were moved to the Assiniboine and Sioux Tribes, who began a conservation herd at their Fort Peck Reservation. In October 2014, the bison were moved to the Fort Peck Reservation because the Fort Peck Fish and Game Department was recognized for managing the bison and testing them for disease. In November, 139 Yellowstone bison from the Flying D Ranch joined the conservation herd at the Fort Peck Reservation.

Certification requires a process that lasts several years and includes keeping animals in fenced pastures near the park boundary. The quarantine program approved by IBMP has three steps. First, bison are captured at the Stephens Creek Bison Capture Facility, where they are separated by age and sex into different pens. A blood sample is taken, and they are tested for brucellosis, with about 30% of the animals qualifying for the program. Bison that test negative for the disease enter quarantine. Next, testing continues until the animals are declared disease-free. Finally, assurance testing involves one more year of isolation with two additional tests before the quarantine ends. The first two steps must happen in a supervised area near the park. In June 2017, APHIS and the Montana Department of Livestock created final rules for quarantine facilities. In 2017, two pens in a Yellowstone bison trap were turned into quarantine corrals with two layers of fencing. These facilities are located at Stephens Creek and Corwin Springs. APHIS manages the quarantine facilities and works with Montana and the Fort Peck tribes to move the bison. The final phase of assurance testing can take place at the Fort Peck Indian Reservation in northeastern Montana.

Tribes and First Nations

Many tribes and First Nations are working to create and care for their own bison herds. This helps protect cultural traditions, support food security, and keep cultural identity strong. Ecocultural bison conservation works to save bison populations, restore natural ecosystems, and support how Indigenous people have traditionally used natural resources. This approach recognizes the special history between bison and Indigenous peoples, as well as the importance of bison in the United States and Canada. The InterTribal Buffalo Council (ITBC) helps tribes return bison to their communities and reservations. This supports the shared history, culture, and spiritual connection between tribes and bison for future generations. The ITBC is a group recognized by the federal government that sends live bison to member tribes and helps them start their own herds. Many bison taken from government-controlled herds have been given to Native American tribes through requests from parks, refuges, or the ITBC. A program called the Bison Conservation Transfer allows bison with Yellowstone genetics that do not carry brucellosis to be sent to tribes and First Nations. This program also helps protect the genetic diversity of bison herds by adding Yellowstone bison to larger groups. The program includes partnerships with Yellowstone National Park, the Assiniboine and Sioux Tribes of the Fort Peck Indian Reservation, federal agencies, state departments, the ITBC, and other organizations.

The ITBC helped build a quarantine facility at the Fort Peck Indian Reservation. They help move bison to tribes and First Nations who will use them to improve the health and genetic diversity of their herds. Tribes that receive bison must be ITBC members and agree to manage the animals for their genetics.

In August 2019, the first bison entered phase three of the quarantine program at the Fort Peck Reservation. The Assiniboine and Sioux Tribes completed the quarantine for 55 male bison captured in March 2018 at Stephens Creek in Yellowstone National Park. Three males and 21 females captured at the same time remained in quarantine at Corwin Springs, near the park’s entrance. By June 2020, 104 bison had been moved to a special corral at the reservation for quarantine. In August 2020, 40 bison that finished quarantine were sent to 16 tribes across the United States, including those in Kansas, Wisconsin, and Alaska. Since 2019, 294 bison have been sent to the Fort Peck Tribes in northeastern Montana. In December 2021, two family groups of bison were transferred for the first time.

The Meskwaki Settlement in Iowa has a herd of about 20 bison living on the southern edge of their community.

In June 2023, 25 bison were moved from Elk Island National Park in Canada to the Blackfeet Confederacy in Montana. These bison were released into the Chief Mountain Wilderness, becoming the first free-roaming bison herd on tribal land since the species nearly disappeared in the 1800s.

Today, bison are legally managed as livestock. This allows tribes to move and manage bison more easily for ceremonies or food. If bison were classified as wildlife, it would change how they are moved, sold, and managed. As wildlife, bison would belong to the public, making it harder for private individuals to buy or transport them. Tribal agencies could still move bison, but they would need permits, especially when crossing state lines. This classification might also lead to more efforts to let bison roam freely on public lands. Some tribes near Yellowstone have legal rights to hunt bison that leave the park, including the Crow, Confederated Salish and Kootenai Tribes, Blackfeet, Shoshone-Bannock, and Nez Perce. These rights have been supported by court decisions. Five tribes in the Yellowstone area have treaty rights that allow them to manage their own bison hunts.

Province and state programs

The Minnesota Bison Conservation Herd is a project run by the Minnesota Department of Natural Resources (MDNR) to care for and grow a group of bison with the strongest and healthiest genes. The Minnesota Zoological Garden (MZG) works with the MDNR to manage the group of bison across four locations: Blue Mounds State Park, Minneopa State Park, the Minnesota Zoo, and Zollman Zoo. This group includes about 130 bison, and the goal is to grow the herd to 500 bison to help ensure bison can live in Minnesota for many years. In Utah and Alaska, three separate herds of free-ranging bison are managed by state wildlife agencies. In Montana, the Montana Fish, Wildlife and Parks started studying how to reintroduce wild bison populations in 2010. A plan to prepare for reintroducing wild bison was created in January 2020 but was stopped in 2021 due to a legal agreement with the United Property Owners of Montana.

Protected areas with bison herds

Bison live in less than one percent of the area they once inhabited, with fewer than 20,000 bison in protected groups on public, tribal, or private lands that focus on conservation. The approximately 500,000 bison raised for commercial use are not counted unless the group also works to protect bison populations.