American bison were nearly exterminated in the 19th century and are slowly recovering through conservation herds, with welfare implications from confinement, genetic management, and the challenges of rewilding.
Bison welfare in conservation herds involves tensions between genetic management needs and the natural behavior of this wide-ranging species. Fenced conservation herds cannot express the long-distance movement and seasonal migration that characterizes truly wild bison populations. Bison subject to roundup for genetic testing, vaccination, or culling experience significant acute stress. The management of brucellosis in Yellowstone bison results in animals being killed when they leave the park boundary in search of winter range, raising welfare concerns about animals moving in response to natural hunger and range requirements. Rewilding efforts that restore bison to larger landscapes with greater movement freedom offer better welfare outcomes alongside greater conservation value.