Researchers say Montana elk are to blame for an animal disease spreading into new areas around Yellowstone National Park.
The finding disputes conventional wisdom that said park bison and wildlife feeding grounds in Wyoming were responsible.
Scientists with the U.S. Geological Survey and other institutions traced transmissions of the disease brucellosis following a recent spike in livestock infections.
They say a strain of the disease that originated in artificial elk feeding grounds in Wyoming is now self-sustaining in Montana. A different brucellosis strain is found in bison.
The findings were published in the May issue of Nature Communications.
Brucellosis causes pregnant animals to prematurely abort their young.
State and federal officials slaughtered thousands of diseased bison over the past two decades to shield livestock outside the park from potential infection.