Ontogenetic change in social context as a cue for a behavioural switch in spiderlings

In many taxa, variations in the early social context are well known to influence the expression of a suite of behaviours later in life. For species living temporarily in groups, relatively few studies have examined how the ontogenetic change in the social context experienced by individuals during their transition from social to solitary influences their responses to environmental variation. It can be hypothesized that the presence of conspecifics during the gregarious phase may constrain the expression of any behavioural changes in response to external variations that would be detrimental to group cohesion and reduce the benefits associated with social life. In this study, we investigated the interplay between early social experience, satiation and ontogeny in the development of aggressive behaviours in juveniles of the solitary spider Agelena labyrinthica. First, we exposed spiderlings to a period of social isolation of similar duration at different ages, while others were continuously reared socially. Second, we examined how feeding influences the onset of agonistic interactions in spiderlings reared in isolation or socially. When spiders were socially deprived, we found that aggressive behaviour towards siblings increased both when they experienced isolation at a later developmental stage and when they were fed. This was in contrast to spiders maintained in groups, which, regardless of their age and whether they were fed or not, remained tolerant. Overall, our study suggests that changes in the social environment during ontogeny set the context for the expression of behavioural plasticity that prepares individuals for living alone. •Late social isolation during ontogeny increases aggression in spiderlings.•Food intake in socially isolated spiderlings increases aggression.•Spiderlings reared socially are less sensitive to environmental conditions.•The expression of behavioural plasticity depends on the social context.