Paleontological record shows bison first appear in Illinois about 8,000 years ago, at one site along the Mississippi River. The continuous presence of bison in Illinois occurs 4,400 years ago and lasts into the early 1800’s. Remains of bison have been found at 134 sites in Illinois. It is theorized that around the year 1600, the decrease in populations of native peoples is possibly related to European introduced diseases. This may have caused an increase in bison populations. The resulting proliferation of bison may have caused more bison to move into the Illinois tallgrass prairie. In Illinois, it is thought that bison preferred to graze in river bottomlands and wooded areas. Bison herds in Illinois were smaller than those out west, ranging in size from 30-300 animals. The last bison was seen and killed in Illinois in 1808.
Midewin always hoped to include bison in its restoration in some form. Even though Illinois didn’t support the massive herds occurring out west, bison had an influence on the Illinois prairie. They turned the prairie soils with their hooves creating places for seeds of new plants to grow. Grasses were grazed to lower heights and created habitats for grassland birds. The soil was enriched by the fertilizer they left behind. Wallows were formed when bison rolled on the land to get a good scratch and coat themselves with mud and dust, to protect their skin from sun burn and insects. Wallows created temporary water pools providing places in spring for amphibians to transform from egg to adult as well as a source of fresh water for animal and man. Later the wallows served as an open space for certain short lived prairie plant species to grow. Further, the bison were a food source for cowbirds, starlings, magpies, and blackbirds. Bison move continuously as they graze. As they graze, bison hooves stir up insects these birds feed on. These birds migrated with the bison who made feeding on insects so easy.
This link in the prairie ecosystem at Midewin has been missing since the early 1800’s. How will adding them back to the restoration effort effect the outcome? We aren’t sure how bison will change the endeavor to rebuild prairie. So, we are considering their addition to Midewin as an experiment. How will the grazing patterns of bison affect the ecosystem and grassland bird habitat? Time will tell us.
Midewin has created an area for this experiment defined by 9 miles of 6 foot tall woven and barbed wire fencing. This experiment site is 1,030 acres in size with 4 pastures divided by a 5 ft. tall interior fence comprised of 5 strands of barbed fencing. A central coral handling facility connects all 4 pastures. This experiment is currently planned to last for 20 years. Topics to be monitored include grassland bird populations, native grass and flowering plant populations, and visitor-bison interaction. The United States Forest Service will adapt the management plan of the land occupied by the bison during this experiment and amend it as needed.
The location for the pasture on Midewin was chosen based on the following criteria. The pastures needed to be in close proximity to the Iron Bridge Trailhead and the proposed location of the Prairie Learning Center. The site needed to be close to the Midewin Headquarters. There should be vast amounts of baseline data for grassland bird populations for this area. A rolling hill topography for panoramic viewing was important. Also, room to divide the area into sub pastures was a priority. A soil type that is conducive to native prairie grasses and forbs was a must. Finally, an area free from any remaining army infrastructure was a necessity.
The land chosen has been continuously modified by agricultural cultivation, cattle grazing, drain tile installation, and vegetation removal since the 1830’s. During the Joliet Army Ammunition Plant era, this land was used for row cropping and livestock grazing.
Three of the pastures the bison were introduced into have non-native grasses as a starting point. The fourth and smallest pasture has been seeded with prairie species for two years prior to the arrival of bison. How will bison affect the restoration of plants in a prairie? We already know that that in the restoration process, grasses dominate the ecosystem to such a degree that they can out-compete the forbs or flowering plants for available resources. The bison diet consists of 93 percent grass, 5 percent of flowering plants, and only 2 percent woody plants. Will using bison as the primary grazers of the dominant native grasses decrease grass populations? If these grasses decrease, will it allow other short lived opportunistic native species to thrive? These and other questions about using large grazers in restoration efforts will be answered as the experiment progresses.Read More