State-space modeling to support management of brucellosis in the Yellowstone bison population

The Yellowstone bison (Bison bison) exemplifies the challenge of conserving large mammals that migrate across the boundaries of conservation areas. Bison in Yellowstone are infected with brucellosis (Brucella abortus). Their seasonal movements can expose livestock to infection. We developed a Bayesian state-space model to reveal the influence of brucellosis on the dynamics of the Yellowstone bison population and to inform decisions on bison management. A model of frequency dependent transmission was superior to a density dependent model in its ability to predict out-of-sample observations of the probability of horizontal transmission (mean square prediction error frequency model = 0.78, density dependent model = 0.91). Conditional on the frequency dependent model, the median transmission rate of brucellosis was 1.86 year-1 (95% equal-tailed credible interval, BCI = 1.5, 2.2). The median of the posterior distribution of the basic reproductive ratio (R0) was 1.76 (BCI = 1.47, 2.36). Serop...