Posterior probabilities for Bayesian areal wombling barriers for four time points of first raccoon rabies case, along with major rivers (blue). Lines are shaded in increasingly darker gray corresponding to increasing probability of being a boundary. The four categories of P(Δij ≥ c | y) are (0.0, 0.4) - white, (0.4, 0.6) – light gray, (0.6, 0.8) - gray, (0.8, 1.0) – dark gray.