Previous studies of wildlife have found that sociability, i.e. level of social engagement, is associated with parasitism. However, the mechanisms behind this link are not always known. Variation in sociability might directly influence behaviours that mediate infection, such as resource-sharing, or might itself depend on other factors that also mediates infection, such as dominance rank. Our study aimed to test these mechanisms in Japanese macaques (Macaca fuscata yakui) on Yakushima, where sociability were found to predict parasitic nematodes infection. We collected behavioural data from one macaque group to assess sociability (through proximity interactions), space-sharing (using GPS tracking), and dominance rank (from dyadic dominance interactions). We collected faecal samples to assess parasite infection indices and genetic relatedness among individuals. We found the sociability-infection link in this group, but preliminary results suggest that resource-sharing networks and social interaction networks are uncorrelated. This indicates that resource-sharing might not be sufficient to explain sociability-infection link in Japanese macaques. We will conduct further analyses on parasite infection, environmental contamination and genetic relatedness to test other possible mechanisms. This research will clarify the mechanism(s) underlying the sociability-infection relationship to better understand the costs and benefits of group living, with relevance for social systems evolution.