For thousands of years, bison roamed North America’s Great Plains in the millions in search of fresh grass and sanctuary from predators. Along the way, bison helped shape and were shaped by the Great Plains ecosystems. The prairies were once one of the most widespread ecosystems in North America, but are now one of the most threatened.

Bison: a keystone species of the prairies
bison
© Parks Canada/Scott Mair

Bison are regarded as a “keystone species” of the plains because they have a ripple effect on every species that lives in this ecosystem. Like the stone found at the top of an arch, if you remove it, the rest of the system will collapse. Their habit of wallowing in the dirt to evade flies opens up new earth for seeds to sprout and animals to create burrows. Bison carry hitchhiking seeds over great distances in their fur. They leave fertilizer in the form of dung in their path. Hundreds of insects lay their eggs in bison poop and in turn feed other creatures, including now-threatened bird species. For thousands of years, bison were also a life-giving source of food for a variety of creatures, including wolves and humans.

As the pressures of the fur trade, agriculture, and settlement of the West encroached on the great bison herds, the prairies were transformed. Within a single human lifetime, bison were reduced to fewer than 1,000 individuals as a result of overhunting and loss of habitat. The native grassland ecosystems and the prairie species that depended upon bison declined with them.

The return of the prairies
Bisons du parc national Elk Island broutant dans la réserve American Prairie au Montana

Bison from Elk Island National Park grazing at the American Prairie Reserve in Montana.

© American Prairie Reserve

Parks Canada and other organizations have worked hard over the past 100 years to bring bison back from the brink. Reintroducing bison and protecting remaining native grassland helps restore the ancient relationships between bison, the plant communities they feed on, and the predators that depend upon them. Bringing back bison is a way of bringing back the Great Plains.

To learn more about Elk Island’s key role in bison conservation, see Canada’s National Bison Story.

How big are bison? What’s the difference between bison and buffalo? What about wood bison and plains bison? Find out all this and more at the Bison FAQ.