Is Sociability Generally Linked to Infection? A Study Based on Rhesus and Japanese Macaques

Parasite infection is one key risk inherent in group living and is considered to influence the formation and evolution of animal societies. Previous studies investigating the relationship between sociability (a measure of an individual's level of social engagement) and parasite infection have yielded mixed results, with some observing positive relationships between social network centrality and infection and others observing negative or no sociability-infection links. Here, we aggregated behavioral and parasitological data from three groups of rhesus macaques (Macaca mulatta brevicaudus) in China and two groups of Japanese macaques (Macaca fuscata and Macaca fuscata yakui) to test whether sociability generally predicts geohelminth infection in macaques with similar social structure. We discovered variability in the relationship between sociability and geohelminth infection across these different groups of macaques, and results did not support a general pattern linking sociability to geohelminth infection. Among the five groups, we found a significant positive relationship between sociability and infection in only one group. These results call into question how generally useful an indicator social network centrality metrics are in predicting geohelminth parasite infection across individuals, at least relative to other factors that influence infection dynamics. We discuss potential confounds when examining relationships between sociability and infection across populations and groups, and encourage future studies that can account for these while focusing on the mechanisms that might link social factors and parasite infection to fully understand this relationship.