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.