Habitat selection under the risk of infectious disease

Question: How does the risk of infectious disease transmission affect individual habitat selection decisions and the resulting spatial distributions of populations? Mathematical method: We use a differential equation model to describe disease dynamics in two habitats coupled by natal dispersal and use an evolutionary game theoretical approach to calculate the evolutionarily stable strategy for habitat choice. Key assumptions: Natal dispersal by offspring with ideal knowledge of habitats. Habitats differ only in resource quality. Fecundity is proportional to intake rate, which decreases with density. We assume density-dependent disease transmission, with infection reducing fecundity or lifespan. Disease may be present in both habitats or the high-quality habitat only. Conclusions: In the absence of disease, our model predicts input matching (i.e. the distribution of individuals matches the distribution of resource inputs). The negative fitness consequences of infection can result in undermatching (underuse of the high-quality habitat compared with input matching), but stable overmatching (overuse of the high-quality habitat) is never predicted. Increasing the risk of transmission increases the degree of observed undermatching when only the high-quality habitat is infected but reduces undermatching when both habitats present a risk of disease. Increasing the cost of infection by reducing fecundity reduces use of the high-quality habitat (undermatching) in both cases. Increasing the cost of infection by increasing mortality rates also reduces the use of the high-quality habitat when both habitats are infected; if only the high-quality habitat is infected, undermatching may initially increase with mortality but eventually decreases.