Bison and Illinois Prairie: Creating Lush Grasslands West of Chicago

To anyone who has lived in an area with bison (Yellowstone National Park employees and certain residents of South Dakota, raise your hands), it's clear that they are formidable animals. They are, in fact, North America's largest native mammals, standing up to 6 feet tall at the shoulder, weighing a ton. They can also totally take out most marathoners, running at 35 mph.

This is the first summer for 30 bison brought to Nachusa Grasslands, a 1,500-acre stretch of prairie and grasslands 95 miles west of Chicago. The tract was pieced together by The Nature Conservancy, starting in 1986. Currently, Jeff Walk and others with the Illinois chapter of the organization are seeding the land with natural grasses and plants: from wild lupine to prairie smoke to golden Alexanders. Nachusa could eventually support a herd of 70 to 110 bison to nibble on those grasses.

That will be a good addition to protected bison lands. Because, while bison now have a U.S. census number of approximately 450,000, fewer than 30,000 of those are in conservation herds. 

Bison were a pretty natural choice for the grasslands for a few reasons, Bill Kleiman said on the Nature Conservancy website: (1) bison self-sufficiency and (2) their ability to make grass grow more lushly. More about those: Bison don't need help birthing calves, and they can stand out in Illinois snow all winter. Secondly, they have a real technique with grass.

Bison maintain patches of grass known as "grazing lawns," which don't burn during prescribed fires because the grass is short. After such a fire, lush grass appears from the blackened areas, creating new grazing lawns. This creates a mosaic of grazing patches that promotes a wide diversity of plants and animals. Their dung, in a bonus result, attracts certain beetles that some scientists believe are a favorite meal of ornate box turtles.

Other great results from bison grazing can include an increase in these: the rare prairie bush clover, which scientists believe requires grazing disturbance to grow well; rare upland sandpiper; and the grasshopper sparrow, the Nature Conservancy said on its website. 

See where else you can find bison in the U.S., on the Nature Conservancy website.

Follow Catherine at @TreesWhales