A notice filed by two environmental groups, the Western Watersheds Project and the Center for Biological Diversity, indicate that they intend to sue the U.S. Interior Department over a petition
to declare bisons an endangered animal, according to the Associated Press.
Bison numbers have decreased by more than 99 percent over the past 200 years, according to the notice filed against the federal government. The two environmental groups had previously submitted a petition to the Department of the Interior for endangered animals
protection status for bisons, but were rejected.
According to Defenders of the Wild, a wildlife conservation group, bisons are the largest land mammals on the North American continent. Bisons weigh an average of 900 to 2,000 pounds and live up to 22 years in the wild. Both the Yellowstone National Park and the Wood Buffalo National Park were once home to thousands of bison - the latter had about 10,000. According to Defenders of the Wild, wood bison are currently listed as endangered but the plain bison is listed as under review.