Bison Beyond the Boundary

Every winter, thousands of Yellowstone's bison follow an instinct that has governed the species for millennia. When deep snow in the park's interior makes forage inaccessible, the animals move toward lower elevation and thinner snowpack. Some of the western bison population follows the Madison River corridor toward West Yellowstone and a peninsula on Hebgen Lake called Horse Butte, where grass often remains accessible through the coldest months.

The moment those bison cross the park boundary, the politics of wildlife management become intensely complicated. Montana ranchers and state wildlife officials have long maintained that bison carry brucellosis, a bacterial disease that can cause cattle to abort their calves, and that bison ranging freely on Montana ranchland creates an unacceptable risk. Though no documented case of wild bison transmitting brucellosis to cattle in a natural field setting has ever been confirmed, bison movements outside the park are tightly managed under a multi-agency plan that can lead to the hazing, capture, or culling of animals that stray beyond designated tolerance zones.

Advocates for bison have spent decades arguing for expanding the areas where the animals can legally roam, pushing toward the historic range they occupied before the near-total extermination of the nineteenth century. The town of West Yellowstone sits at the center of these competing interests. In years of heavy snowpack, bison sometimes wander into the town itself, crossing side streets in the early morning hours, indifferent to the occasional tourist fumbling for a camera. The bison have no interest in the town's jurisdictional boundaries, which is precisely what makes the management problem so persistently difficult to resolve.