Invasive Species Management in Two-Patch Environments: Agricultural Damage Control in the Raccoon (Procyon Lotor Problem, Hokkaido, Japan)
Koji Kotani Hiromasa Ishii Hiroyuki Matsuda Tohru Ikeda
We develop discrete-time models for analyzing the long run equilibrium outputs on invasive species management in two-patch environments with migration. In particular, the focus is upon a situation where removal operations for invasive species are implemented only in one patch (controlled patch). The new features of the model are that (i) asymmetry in density dependent migration is considered, which may originate from impact of harvesting as well as heterogeneous habitat conditions, and (ii) the effect of density-dependent catchability is well-taken to account for the nature that the required effort level to remove one individual may rise as the existing population decreases. The model is applied for agricultural damage control in the raccoon problem that has occurred in Hokkaido, Japan. Numerical illustrations demonstrate that the long run equilibrium outputs highly depend on the degree of asymmetry in migration as well as the sensitivity of catchability in response to a change in the population size of invasive species. Furthermore, we characterize the conditions under which the economically optimal effort levels are qualitatively affected by the above two factors and aiming at local extermination of invasive species in the controlled patch is justified.