We refer to this model as the ''neighboring model'' H neigh (l), where l denotes the set of free parameters in the model (in addition to b 0 M , b 0 F , e 0 M and e 0 F that are always freely variable). The metapopulation model considers that viral exchange is more intense between populations from the same metapopulation than between populations from different metapopulations. A simple way to test this hypothesis is to assume that populations belonging to the same metapopulation have the same external transmission rate, and that this external transmission rate differs between populations from different metapopulations. We define the ''male metapopulation model'' H M meta l ð Þ, where e i M represents the value of e M in metapopulation i, and l denotes the set of free parameters in the model (in addition to to b 0 M , b 0 F , e 1 M , e 2 M and e 3 M that are always freely variable). Note that in this model the only parameter that differs between cat populations is e M , which varies among metapopulations (e 1 M , e 2 M , e 3 M depending on the metapopulation). Finally, we also define the ''female metapopulation model'' H F meta l ð Þ, which is strictly equivalent to H M meta l ð Þ, except that it pertains to female external transmission rates.