To start with, we look at the impact of the population characteristics (the sex-ratio in captured cats SR obs ; the estimated population size, i.e. the number of captured cats N obs ; the number of captured males in the cat population M obs = SR obs N obs ; and the mean age of captured males and females, AM obs and AF obs , respectively). Results are summarized in Table 2 . The only significant effect we found is associated with the effect of mean age of males (x 2 = 4.09, 1 df, p = 0.043) and females (x 2 = 5.335, 1 df, p = 0.02) on the male-tofemale transmission rate (b AM F and b AF F , respectively). Interestingly, there is a negative correlation between the mean ages of males and females and FIV prevalence (b AF