Sex-specific associations between social behaviour, its predictability and fitness in a wild lizard

Social environments impose a number of constraints on individuals’ behaviour. These constraints have been hypothesized to generate behavioural variation among individuals, social responsiveness, and within-individual behavioural consistency (also termed ‘predictability’). In particular, the social niche hypothesis posits that higher levels of competition associated with higher population density should increase among-individual behavioural variation and individual predictability, as a way to reduce conflicts. Being predictable should hence have fitness benefits in group-living animals. However, to date, empirical studies on fitness consequences of behavioural predictability remain scarce. In this study, we investigated the associations between predictability of social behaviour and fitness in the eastern water dragon (Intellagama lesueurii), a wild gregarious lizard. Since this species is sexually dimorphic, we examined these patterns both between sexes and among individuals. Females, which were more sociable than males, exhibited slightly higher levels of among-individual variation but similar social predictabilities as males. Females that were more sociable were also more predictable while no association was found between social behaviour and predictability in males. Finally, social behaviour and its predictability showed sex-specific associations with survival and reproductive success. These findings partly support predictions from the social niche hypothesis and highlight the importance of behavioural predictability in social evolution.