Photo by Dee Hudson

November 1, 2018

Returning Bison to the Illinois Landscape

Nachusa Grasslands, located near Franklin Grove in Lee County, is a remarkable conservation effort to preserve the natural ecosystem and wildlife native to Illinois.

The Nature Conservancy (TNC), a private nonprofit conservation organization, bought 125 acres in 1986 and started creating a grassland that replicates those that once covered that Prairie State, complete with vistas of waving grasses dotted with bright-yellow sunflowers, neon-pink coneflowers and richly purple blazingstars. Today the tallgrass prairie spreads across 3,500 acres and in 2014 an additional historic element of the prairie ecosystem was introduced—bison (Bison bison), the largest mammal on the North American continent.

Bison grazing on the prairie
Photo by Dee Hudson

Most scientists believe bison officially disappeared from our landscape in 1830. Today, bison range across 1,500 acres at Nachusa and TNC is coordinating efforts to understand how the bison are contributing to the health of prairie and what effects they have on plant and animal communities.

“Our goal is to create a large and diverse grassland that supports the full complement of prairie wildlife, with bison helping us regain a naturally occurring ecological function that had been absent for nearly 200 years,” Bill Kleiman, Project Director of Nachusa Grassland, remarked. “When I started at Nachusa in 1993 I was presented a t-shirt with a picture of a bison on the prairie and the words ‘The Vision.’ In 2010 my colleague Cody Considine and I started talking about what it would it take to make it happen, and we started planning, obtaining approvals and getting the infrastructures in place that resulted in the arrival of bison in 2014.”

Bison cow and calf
Photo by Greg Baker

Thirty genetically pure bison (no cow genes) were released onto the grasslands in October 2014 and today the herd has reached its optimum size of about 130.

“If we were trying to grow the herd as a farmer we would focus on having more females than males, but because our goal is to have the herd replicate a historic, wild herd, we are striving to have about an equal number of males and females,” Kleiman explained. “From a genetics standpoint, an equal number is better.”

The Nachusa Grassland project is unique from many perspectives. First, bison are being reintroduced to a prairie east of the Mississippi River. Secondly, the Nachusa project is taking place on a restored prairie landscape, whereas other bison reintroductions have taken place on remnant prairies and pastures. Finally, the project entails managing the animals as a conservation herd and allowing for conservation grazing to take place.

According to Kleiman, “Without grazers the mature prairie would be expansive stands of 6-foot tall grasses. If you look around the preserve today you initially would see large plots that look ungrazed, but on closer examination you would actually see patches where light grazing has occurred. The patchiness of conservation grazing creates a heterogenous structure to the landscape that supports a variety of grassland species.”

Twenty-two fenced exclosures, or bison-free zones, were created prior to the release of bison, providing research study plots to assess the effects bison have on plant and animal communities.

A Living Laboratory

Bison calf
Photo by Greg Baker

Since 2014, The Nature Conservancy has partnered with numerous researchers to monitor how the reintroduction of free-ranging bison is impacting the biological and chemical composition of the prairie ecosystem. Researchers will re-survey the plots every three years.

“It will take time to start seeing changes,” said Dr. Elizabeth Bach, Nachusa Grassland Ecosystem Restoration Scientist. “Over the next several years we will be publishing reports and papers on all aspects of the research and management actions taking place at Nachusa—vegetative changes, responses of grassland wildlife, use of prescribed fire in oak woodlands and management of invasive species. Our goal in this long-term study is to understand what techniques help native plants and animals thrive at a landscape scale. Restoration ecology is a new field and we have an enormous opportunity to use the Nachusa project to contribute to emerging science about natural area management.”

Kleiman and Bach have some interesting, anecdotal observations on changes to the prairie post bison introduction.

the face of a Bison calf
Photo by Charles Larry

“We find bison hair everywhere,” Kleiman said. “Just months after the bison arrived we were finding bison hair in mouse nests constructed under boards researchers had placed as snake habitat, and grassland birds are using it in their nests. It is amazing how quickly they have learned to use this resource.” Other changes they have noted are the creation of grazing lawns and wallows, or the shallow scrapes where bison dust bathe.

The efforts to maintain the natural grassland landscape in Illinois through conservation and bison repopulation is an opportunity to learn about seeing life from a lost perspective. The Nachusa Grasslands website ( and Facebook page offer ways to learn more, and are excellent resources to view photographs, review regulations and stay informed on the most recent conservation efforts.

Herd of bison
Photo by Charles Larry

A partial list of the Nachusa Grasslands research topics and institutions;


Dickcissel. Photo by Dee Hudson
  • Habitat selection of reintroduced bison, Julia Brockman, MSc student (completed), and Dr. Clayton Nielsen, Southern Illinois University Carbondale, and Jeff Walk, The Nature Conservancy
  • Determining bison diet and bison effects on vegetation in a chronosequence of restored prairie at Nachusa, Ryan Blackburn, MSc student (completed), and Dr. Holly Jones, Northern Illinois University
  • Long-term monitoring of plant community composition with reintroduction of bison grazing, Dr. Sara Baer, Southern Illinois University, Dr. John Taft, Illinois Natural History Survey and University of Illinois Urbana-Champaign, and Dr. Elizabeth Bach, The Nature Conservancy


Badger. Photo by Dee Hudson
  • Grassland bird response to restoring historic tallgrass prairie, Heather Herakovich, PhD candidate, and Dr. Holly Jones, Northern Illinois University
  • Prairie birds in agriculture: Examining the use of surrounding agricultural habitat by birds that live in prairies, Megan Garfinkel, PhD candidate, University of Illinois Chicago


Meadow-Jumping-Mouse in the hands of a biologist
Meadow-Jumping-Mouse. Photo by Dee Hudson
  • Small mammal monitoring and the effects of invasive plant removal, Nicholas Steijn, MSc graduate student, and Dr. Holly Jones, Northern Illinois University
  • Prairie engineers: Investigating species associations of burrows in a world class prairie restoration, John Vanek, PhD student, Northern Illinois University


  • Effects of management on functional diversity in restored tallgrass prairie plant communities, Anna Farrell, MSc graduate student, and Dr. Nick Barber, Northern Illinois University
  • Low pollination of state-endangered downy paintbrush: A problem for restored prairies or for Illinois? Katherine Wenzell, PhD student, and Dr. Krissa Skogen and Dr. Jeremie Fant, Chicago Botanic Garden and Northwestern University
  • Impacts of mycorrhizal fungi abundance and diversity on establishment of Commandra umbellate, Emma Leavens, MSc student, and Dr. Greg Mueller, Chicago Botanic Gardens and Northwestern University
  • ong-term monitoring of endangered prairie bush clover, Dr. Pati Vitt, Chicago Botanic Garden


  • Fire research and demonstration plots, Jeff Walk, Bill Kleiman and Cody Considine, TNC
  • Restoring Function in Grassland Ecosystems (ReFuGE Project) Dr. Holly Jones and Dr. Nick Barber, Northern Illinois University
  • Plant diversity effects on soil N2O emissions, Drew Scott, PhD candidate, and Dr. Sara Baer, Southern Illinois University Carbondale
Photo by Charles Larry

Kathy Andrews Wright is retired from the Illinois Department of Natural Resources where she was editor of Outdoor Illinois magazine. She is currently the editor of Outdoor Illinois Wildlife Journal and Illinois Audubon magazine.

Rachel Wolfe was born and raised in northern Illinois and currently lives in Norway where she just completed her first assignment for BBC. Environmental conservation and the human connection to nature holds a central theme in her writing, photography and artistic projects.

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