Spacing behaviors and spatial recruitment of a wild rodent in response to parasitism

Host spacing may benefit the parasites (e.g., enhance parasite transmission) or the hosts (e.g., reduce host infection), with profound consequences in epidemiology and host-parasite dynamics. In this study, we tested parasitism effects of intestinal nematodes on spacing behaviors and spatial recruitment of the Taiwan field mouse (Apodemus semotus). We tracked the locations of resident mice for 84% of the host population, with half of them experimentally reduced of their parasitic infection. We interpolated geo-tagged data on parasite egg counts of the resident mice to create an infection risk landscape and extracted the risks to the locations of newly recruited mice. We performed parentage analysis to identify mother-offspring pairs, which allowed us to test whether in situ recruits moved toward lower-risk areas during natal dispersal. We found that the less-infected mice became spatially aggregated compared to the more heavily infected, and the juvenile recruits occurred preferentially in lower-risk areas compared to the landscape, the residents, and their natal places. The spatial aggregation of less-infected resident mice and the association of juvenile recruits with lower-risk areas could hinder parasite transmission. This study provided some empirical support for a potential link between host recruitment process and parasitism risks.