2.3 Mortality, reproduction, dispersal
Besides lethality, we considered also natural and hunting mortality rates. For natural mortality we applied a 0.18 annual rate to juveniles and 0.12 to the other two age classes (Toïgo et al., 2008). Individuals who died of natural causes were transferred directly to the “non-infectious carcass” compartment of the model. Hunting rate in the post-recruited population was initially set at 0.3 for all age classes. Then, to test for the effect of an increased hunting pressure on virus persistence probability, we also ran additional scenarios in which hunting pressure ranged from 0.4 to 0.6.
At the beginning of each year, each female wild boar was assigned a reproductive state, controlled by an age and density-dependent reproduction probability. All reproductive females were assigned a delivery reproduction day, ranging from 1 to 60, to allow for a uniform distribution of births during the birth season. Litter size was set to 4 for juveniles, 5 for yearlings, 6 for adults (Bieber and Ruf, 2005). Then, in the assigned day, they gave birth to the age-specific number of piglets with a 50:50 sex ratio. The piglets coordinates initially corresponded to those of their mother.
At the beginning of the dispersal season, all yearling individuals were assigned a dispersal state, generated through a sex-specific dispersal probability (0.7 for males, 0.4 for females; Truvé et al., 2004), a dispersal starting day, ranging from 1 to 40, and a dispersal duration ranging from 1 to 14 days for males, from 1 to 7 days for females (Truvé et al. 2004). Then, each day and for the entire duration of the dispersal season, each dispersing individual moved from its current cell to the neighbouring cell with the lowest wild boar density, thus mimicking the effort by dispersing animals to avoid intra-specific competition for resources. All model parameters are summarized in Tab. 1.