Why the American Bison Is Endangered

Millions of bison once roamed North America.

American bison in field
Bison were critical in the lives of the Plains tribes. Scott Suriano / Getty Images

The American bison is North America’s largest land animal and the national mammal of the U.S. It was nearly driven to extinction by habitat loss and hunting. An estimated 30 to 60 million bison roamed North America until the late 1800s, when bison numbers dwindled to fewer than 1,000.

Thanks to conservation efforts, the bison's numbers are now stable, and it is no longer endangered. Today, about 30,000 bison live in conservation-focused herds throughout North America. Another 400,000 or so are raised as livestock on ranches and farms.


Historically, the greatest threats to the bison were hunting and habitat loss. Today, with their population numbers so low, they now also face threats from low genetic diversity.


Bison were critical in the lives of the Plains tribes. Native Americans used the animals for food and their hides for clothing and to make shelter. They also made tools and ceremonial items from the bison. They relied on the bison for survival, according to the National Wildlife Federation.

In the 1800s, settlers began moving into Native American land. They slaughtered millions of buffalo for food and sport. Recognizing the importance of the animals for the Plains tribes’ survival, they killed the bison in spite of Native Americans. By the late 1800s, the bison population had dropped to fewer than 1,000.

Habitat Loss

When bison roamed millions of acres, their grazing kept both the grasslands and herds healthy and diverse, according to the WWF. But in addition to hunting bison for food and sport, early settlers also cleared the land where the bison roamed. They worked to make room for their own livestock, which took away from the bison’s habitat, leaving the remaining bison with little land left.

Bison walking through Black Sand Basin
Yellowstone is the only place in the U.S. where wild bison have lived continuously since prehistoric times. Lidija Kamansky / Getty Images

The largest remaining wild herd of bison consists of about 4,500 animals at Yellowstone National Park. Using fossils and stories from early travelers, researchers believe that Yellowstone is the only place in the U.S. where wild bison have lived continuously since prehistoric times. 


There are only about 30,000 bison currently in conservation herds (herds managed by government and conservation organizations). These small herd sizes result in a loss of genetic diversity, as the gene pool for breeding is so small.

In the late 19th and early 20th century, some ranchers who owned some of the dwindling bison population bred them with cattle in hopes of creating healthier livestock and heartier meat animals.

According to the WWF, scientists believe there are only two public bison herds that show no evidence that they’ve been bred to cattle: Yellowstone and Elk Island National Park in Canada. Conservation groups have been working to establish additional non-hybrid herds in other locations. It’s critical to protect the bison’s genetics because a disease outbreak or other key event could threaten those herds.

What We Can Do

Although the bison’s numbers are nowhere near what they used to be, their population is stable and many call the animal a conservation success story.

Various groups are working with national parks, Native American communities, and ranchers to restore bison to their natural habitat.

Co-founded in 1905 by President Theodore Roosevelt and Bronx Zoo Director William Hornaday, the American Bison Society is part of the Wildlife Conservation Society. The group’s goal is the cultural and ecological restoration of bison across North America. (You can donate to WCS for bison conservation.)

The WWF works with several tribal communities throughout the Northern Great Plains to restore bison and other wildlife, including the endangered black-footed ferret, to its original habitats. You can financially pledge to support the effort or symbolically adopt a bison.

Established in 1992, the Intertribal Buffalo Council works with the National Park Service to coordinate transferring bison from parks to tribal lands. The group worked with the National Bison Association to name the bison the national mammal of the U.S. as part of the Bison Legacy Act of 2016. You can donate to the group to help move bison to tribal plains.

Frequently Asked Questions
  • Is it legal to kill bison?

    Besides some private ranches that allow hunting on their land, only the states of Utah, Wyoming, Montana, Arizona, and Alaska allow bison hunting during specified times. Hunters must have tags and a permit to hunt bison on public lands.

  • Is it legal to eat buffalo?

    Wild American bison share their species name with domestic American bison, which are bison raised for meat. It is legal to eat bison that has been raised for this purpose, but it isn't legal to hunt for bison without a permit.

  • What would happen if bison went extinct?

    Bison are a keystone species in Yellowstone National Park, where North America's largest remaining wild herd still roams. Other species in this region rely on them for food and population control. They also have a symbiotic relationship with the prairie grasses—as the bison graze, they distribute grass seeds with their feet.

  • What's the difference between buffalo and bison?

    Bison and buffalo are, in fact, different animals. Bison are the animals that graze in Yellowstone National Park whereas buffalo roam abroad (for instance, the water buffalo in South Asia and the cape buffalo in Africa). In the U.S., both terms are widely used and accepted to mean the species Bison bison, American bison.

View Article Sources
  1. "Bison by the Numbers." National Bison Association.

  2. Aune, K. "American Bison." IUCN Red List of Threatened Species, 2016, doi:10.2305/iucn.uk.2017-3.rlts.t2815a45156541.en

  3. Kohler, Judith. "6 Amazing Facts You Never Knew About Bison." The National Wildlife Federation Blog, 2012.

  4. https://www.nationalgeographic.com/animals/mammals/facts/american-bison

  5. "Plains Bison." World Wildlife Fund.