American bison were reduced from 60 million to fewer than 1,000 in the 19th century. Their remarkable recovery raises new welfare questions about management of wild-roaming herds.
Bison welfare challenges center on the conflict between their need for free-ranging movement and the constraints of property boundaries and livestock disease regulations. The Interagency Bison Management Plan in Yellowstone results in thousands of bison being hazed, captured, and slaughtered each year to prevent brucellosis transmission to cattle — despite very limited evidence of actual transmission risk under natural conditions. Individual bison experience significant stress and injury during hazing operations. The restriction of the only large free-roaming bison population to a single park creates genetic and behavioral constraints that compromise population-level wellbeing.