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Meet the bison: facts about America's national mammal

A bison in the snow in Yellowstone National Park.

Bison are the largest native grazer of America’s Northern Great Plains. This charismatic species that once roamed the grasslands freely by the tens of millions experienced a devastating blow to its population when the westward expansion of European settlers and market hunting pushed them toward extinction in the 1880’s.

Beginning in 1905, the American Bison Society and the US government launched a campaign to save the species from extinction and restore bison numbers, an effort that succeeded but ended in 1935. Since that time numbers have been stable, but small herd sizes have put bison genetic health and diversity at risk.
WWF will address this challenge through our work to restore large herds at multiple sites.

Take a look at why bison are unique to our landscape and what WWF is doing to help.

Bison in Yellowstone National Park

1. How much do bison weigh?
North America’s largest terrestrial mammal, bison can weigh up to a whopping 2,000 pounds, reaching a length of up to 12 feet. Despite their mass, they can still hit speeds of 40 miles per hour when running.


2. What do bison eat?
Bison are principally grazers, consuming the grasses of the Northern Great Plains. They tend to eat a more varied diet of flowering plants, leaves of woody plants, and lichens in the summer and fall. Come winter, bison use their massive heads powered by their muscled humps to sweep aside snow to forage for buried food.


Bison facing front with herd behind

3. Why did bison almost go extinct?
Tens of millions of bison once roamed America’s grasslands. But over the course of a few decades in the late 1800’s, they were nearly gone as people hunted them principally for their hides to fuel the European industrial revolution. By the 1930s, our nation’s leaders succeeded in restoring a small fraction of the population to public lands. WWF is continuing the work to ensure that large herds of bison are established and expanded on public and tribal lands in the Northern Great Plains.


4. How does WWF help conserve bison?
WWF works with public, private and tribal entities to help protect bison. We’re identifying opportunities and creating places where bison can thrive in large herds—of more than 1,000 bison each—on vast landscapes in the Northern Great Plains. WWF scientists also conduct research on bison diet, freshwater use, grassland birds, and fire/grazing interactions to understand the role bison play in the ecosystem.


A bison covered in snow in Yellowstone National Park

5. Why are bison considered survivors?
Bison can live through the extreme heat and blizzards of the Great Plains that often threaten the survival of other contemporary native and domestic grazers. WWF is committed to ensuring not only the survival of the species but to reestablishing bison in numbers and at scale in suitable landscapes to secure the long-term genetic health of this ice age survivor.