Fig. 4.

The approximative solution to the transmission dynamics given in Eq. (23) (applied where we have set $t_{\text{pul}}=2\text{years}$ and Eq. (18) as the solution to the dynamics before this point) against the full solution to the dynamics obtained numerically by solving the equivalent system with Eqs. (1) and (2), each represented by the coloured solid and dashed lines, respectively, for a range of initial conditions M(t₀). All lines and the grey region correspond to their equivalent values in Fig. 2, where an additional upper and lower panel split in this set of figures compares the relative dynamical behaviour under the influence of a migration perturbation of $\beta \delta L\left(t_{\text{pul}}\right)=+1(-1){\text{years}}^{-1}$ for the upper (lower) pair of panels.