WILMINGTON – There are newborn bison calves grazing at the U.S. Forest Service’s Midewin National Tallgrass Prairie in Wilmington.

The U.S. Department of Agriculture’s Forest Service branch, which operates Midewin, announced the news Wednesday. Bison were introduced at Midewin in October 2015 as a 20-year experiment to see if their grazing pattern, which creates more varied grass lengths, helps attract birds that are native to Illinois tallgrass prairies.

The original herd of four bulls – genetically 100 percent pure bison from Yellowstone National Park – and 23 cows – from a ranch in South Dakota – produced several baby bison last year. When the herd was introduced to about 1,200 acres of prairie at Midewin, each female already was pregnant.

That means the latest newborns are the first ones created on-site.

The bison range can be accessed via the Iron Bridge Trailhead on Route 53 at the intersection of South Chicago and Hoff roads. For a longer trek, the range also can be accessed via the Wauponsee Glacial Trail. There is fence system that keeps the herd within the 1,200-acre pasture.