A genetically pure herd of American bison has been living in Utah's Henry Mountains, a discovery offering new hope that wild herds can be expanded to once again roam freely in the West.

Most bison alive today have been interbred with cattle after the iconic prairie species was nearly hunted to extinction. But, scientists having run DNA tests on some of the 350 bison in the Utah herd have now confirmed they are direct descendants of roughly 20 wild bison transferred from Yellowstone National Park in 1941.

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The Utah herd, though grazing closely by cattle, showed no signs of brucellosis – a livestock disease that ranchers fear bison could spread if reintroduced to parts of the country.

"This is a remarkable finding considering these free-roaming, legally hunted animals live on unfenced public lands and graze alongside livestock," Johan du Toit, wildlife ecologist from Utah State University, and one of the researchers said.

He adds that the herd could be an important resource in restoring bison to their historic range across the American West.

The researchers published their findings in the journal PLOS One.

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