Bison (Bison bison) and elk (Cervus elaphus) in the greater Yellowstone ecosystem have long been infected with Brucella abortus. The continued culling of large numbers of Yellowstone bison to reduce the risk of brucellosis transmission to cattle could negatively affect long-term conservation. A desirable management objective is to reduce the level of B. abortus infection while conserving wildlife populations. Identifying the ecological factors that influence immune suppression and vulnerabilityto infection will help initiate effective control measures. Seasonal food restriction during pregnancy has the potential to limit resources available for immune defence and may be an important factor sustaining brucellosis in wild ungulate populations. Consequently, effective management practices will need to include a diverse range of integrated methods, which include maintaining separation of livestock and wildlife, managing habitat to reduce brucellosis transmission, and reducing disease prevalence in wildlife. The long-term success of these management practices will depend on sound science and support of the stakeholders involved.