The spiders that lost their personalities: assessing long-term behavioural individuality in social Stegodyphus dumicola

Across animal taxa, many species show behavioural individuality, that is, repeatable between-individual differences in behaviour. Numerous studies link behavioural individuality to major ecological and evolutionary processes. Here we conceptualize how such links hinge critically on the often untested assumption that individuality persists over long-term, ecologically relevant time frames. We test this assumption in an emerging model, the social spider Stegodyphus dumicola , by assaying individuals every 2 weeks, for a total of nine times over 4 months for three different behavioural phenotypes: boldness and fleeing in solitary settings, and prey capture latency in a social setting. Repeatable differences in boldness and fleeing were initially strong but faded within weeks and failed to predict behaviour later in life. Only fleeing remained moderately repeatable at the end of the study period. Prey capture in a social setting was not repeatable throughout the study period. Our results suggest that care must be taken when attempting to link short-term individuality, that is assumed to represent stable trait values, with ecological and evolutionary outcomes. We discuss the importance of quantifying both long-term repeatability and plasticity of behaviour, by using repeated assays across ontogeny in model organisms, to fully understand links between individuality and ecological and evolutionary processes. • Personalities were not long lasting in social spiders studied over 4 months. • Repeatability of behaviour was initially strong but faded after a few weeks. • Documented short-term animal personality cannot be assumed to be long lasting. • Studies linking personality to evolution must control for developmental stage. • Establishing repeatability across ontogeny in animal models is encouraged.