Yellowstone National Park's bison have long been prisoners, hazed back to the park or slaughtered whenever they head for lower winter range. That's because half the herd tests positive for exposure to brucellosis, an abortion-causing disease that ranchers fear will spread to cattle (although outbreaks around Yellowstone have been traced to elk). In 2011, however, agencies OK'd a plan to let the shaggy beasts roam from the park onto 75,000 acres of winter range near Gardiner, Mont. ("Yellowstone bison get more room to roam," HCN, 5/16/11).
In January, the Montana Board of Livestock rejected a proposal that would have opened additional lands to bison and let the bulls – which pose little risk of transmitting brucellosis – roam the Gardiner Basin year-round. Then park administrators nixed a controversial plan to vaccinate bison with "biobullets," claiming the alleged benefits didn't justify the cost. That means the slaughter and hazing will continue – and with the herd's population increasing by 9 percent annually, the problem won't go away.