Are males aggressive to rivals also aggressive to predators? Testing the behavioural correlation hypothesis and predator pressure hypothesis on antipredator behaviour in social spider mites

Behavioural correlations, such as consistent levels of aggression across social and anti-predator contexts, are commonly observed in animals. In social spider mites of the Stigmaeopsis miscanthi species group, males vary in their aggression toward conspecific rivals, and also exhibit cooperative defence behaviours against intrusive predators into their nests. We tested whether male–male aggression is positively correlated with antipredator aggression (behavioural correlation hypothesis), or whether variation in antipredator aggression reflects local differences in predation pressure (predator pressure hypothesis). We compared counterattack success against predatory mite larvae (Typhlodromus bambusae) among three species/forms with differing male–male aggression: S. miscanthi mild aggression (ML) form, high aggression (HG) form, and S. sabelisi. Contrary to predictions of the behavioural correlation hypothesis, S. miscanthi ML form showed the highest counterattack success despite having intermediate male–male aggression. A survey of predator fauna revealed that predator composition differed among three species/forms, supporting the predator pressure hypothesis. Notably, S. sabelisi was predominantly exposed to predatory gall midge, while S. miscanthi ML form and HG form faced more predatory mites. Our findings suggest that predator community structure drives antipredator behaviour more strongly than behavioural correlations with male–male aggression.