In the evolutionary transition from solitary to group living, it should be adaptive for animals to respond to the environment and choose when to socialise to reduce conflict and maximise access to resources. Due to the associated proximate mechanisms (e.g. neural network, endocrine system), it is likely that this behaviour varies between individuals according to genetic and non-genetic factors. We used long-term behavioural and genetic data from a population of eastern water dragons (Intellagama lesueurii) to explore variation in plasticity of social behaviour, in response to sex ratio and density. To do so, we modelled individual variation in social reaction norms, which describe individuals’ mean behaviour and behavioural responses to changes in their environment, and partitioned variance into genetic and non-genetic components. We found that reaction norms were repeatable over multiple years, suggesting that individuals consistently differed in their behavioural responses to changes in the social environment. Despite high repeatability of reaction norm components, trait heritability was below our limit of detection based on power analyses (h2 < 0.12), leading to very little power to detect heritability of plasticity. This was in contrast to a relatively greater amount of variance associated with environmental effects. This could suggest that mechanisms such as social learning and frequency-dependence may shape variance in reaction norms, which will be testable as the dataset grows. --