At the onset of the harsh winter of 1996-1997 in the Greater Yellowstone Area (GYA)[fn¹], the YNP bison population was more than 3,400. Record numbers of bison (Bison bison) left the park in search of forage, and others starved. As bison crossed into private lands and lands managed by federal agencies other than the National Park Service, national attention focused once again on management strategies—including shooting bison—used to prevent the potential spread of brucellosis to cattle that are grazed on land adjacent to the park.

Brucellosis in the GYA is a disease caused by Brucella abortus biovar 1, a bacterial organism transmitted primarily by contact with products of birth or abortion or by milk. In response to public discussion of whether brucellosis transmission by bison or elk (Cervus elaphus) is a threat to domestic livestock and whether vaccination or other management strategies might prove useful in controlling potential transmission, Secretary of the Interior Bruce Babbitt asked the National Academy of Sciences to undertake a 6-month study of brucellosis in the GYA. The Board on Agriculture and the Board on Environmental Studies and Toxicology began the study in May 1997. The study specifically addressed

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