2.4. Comparing models to data. Models cannot be directly compared with data because they predict distributions for the total number of infected and susceptible males and females in the population, whereas data are just samples of the real total numbers, i.e. the probability of capture is strictly below 1. To simplify, we assume that the total number of males and females in the populations are proportional to their observed values, i.e. M = M capt (1+p NC ) and F = F capt (1+p NC ), where p NC is a constant (1/(1+p NC ) is the proportion of captured cats) and M and F are the real numbers of males and females within the population, respectively. Based on the ratio between the number of cats captured through baited traps and the number of cats observed through intense monitoring in each population, we estimate that p NC is equal to 0.3 in average.