The herd’s expansion is an obvious sign that the animals are historically suited to the area, but other data supports the project’s mission of letting the bison herd’s roaming, grazing and fertilizing maintain the prairie. Without that activity, it’s almost impossible to maintain the unique biodiversity of the prairie grasslands.

Researchers have found that smaller mammals, such as mice and voles, are building nests of bison hair, and that swallows can be seen hovering over the herd, feeding on insects attracted to the bison. These developments confirm that the entire ecosystem is healthier, with growing animal and insect populations, which will eventually attract a wider array of species to the area.

Intensive hunting virtually wiped out the bison east of the Mississippi as far back as the 1830s. Over the last several decades many small herds have been brought back to farms and ranches in the Midwest, but the Nachusa herd has several traits that distinguish them from bison already being raised in Illinois.

The Nachusa bison have not been interbred with cattle, according to the conservancy. They are direct descendants of the original North American bison population that was saved from extinction at the beginning of the 20^th century. The Illinois herd remains “wild,” with human interaction only once a year for a quick veterinary checkup.

COMMENT: Bison do well on Advanced Biological Concept’s cafeteria style mineral program. Even 500 acres to roam on is still relative confinement and does not allow adequate natural access to balanced minerals. ABC’s program mimics the historical availability of natural mineral licks to provide the necessary array of minerals.