Growing up with nutritional stress leads to peripheral social network positions, independent of ‘personality’

Abstract

Social integration predicts life span in gregarious species, including humans, but the causes of variation in social integration and its link to behaviour (‘personality’) in other domains are not well known. Early life conditions also shape fitness variation, possibly through effects on personality and social integration. We studied social integration in zebra finches, Taeniopygia castanotis, reared with different levels of nutritional stress, which we showed to affect offspring growth and thereby fitness prospects. Growing up with nutritional stress caused individuals to attain more peripheral positions in social networks, as they interacted (1) with fewer individuals, (2) less frequently with their connections and (3) less with well-connected (i.e. ‘popular’) individuals. Thus early-life adversity effects on social integration may mediate effects on fitness. In contrast, behaviour in five standardized tests was independent of early life adversity, and consistent with these findings, behavioural scores were at most weakly predictive of network position. Choice of interaction partner did, however, depend on personality, with individuals interacting assortatively with respect to gregariousness and disassortatively with respect to boldness. Thus, developmental conditions may affect fitness prospects through effects on social integration, independent of ‘personality’, and suggest that some level of (social) challenge is required to reveal carry-over effects of early development.