Parasitism and host social behaviour: a meta-analysis of insights derived from social network analysis

Social behaviour is a key component of animal behaviour that facilitates the spread of parasites. Traditionally, group size has been used as a primary metric for quantifying the impact of social behaviour on parasite transmission; however, with the emergence of social network analysis an increasing number of studies are using this more nuanced tool to study links between social behaviour and parasite infection. In this study, we synthesized insights derived from empirical studies on social networks and parasites using a meta-analytical approach. We analysed 210 associations between parasite burden and individual level network metrics extracted from 18 published articles. Overall, we found a positive effect of social behaviour, measured by social network metrics, on parasite infection at the individual level, with no evidence of publication bias. The magnitude of the mean effect size for associations between social network metrics and measures of parasitism was nearly twice as large as that observed for group size in previous meta-analyses. However, there was significant heterogeneity in effect sizes across studies, and this pattern could not be explained by either host traits, parasite traits or the social network metric examined. We discuss potential reasons for this unexplained heterogeneity, such as possible mismatches between focal host social behaviour and focal parasite biology as well as methodological considerations. We also suggest future research directions that can help fill gaps that remain in our understanding of the drivers of variation in interactions between social hosts and parasites.