Abstract
The quantity and quality of social relationships, as captured by social network analysis, can have major fitness consequences. Various studies have shown that individual differences in social behaviour can be due to variation in exposure to developmental stress. However, whether these developmental differences translate to consistent differences in social network position is not known. We experimentally increased levels of the avian stress hormone corticosterone (CORT) in nestling zebra finches in a fully balanced design. Upon reaching nutritional independence, we released chicks and their families into two free-flying rooms, where we measured daily social networks over five weeks using passive integrated transponder tags. Developmental stress had a significant effect on social behaviour: despite having similar foraging patterns, CORT chicks had weaker associations to their parents than control chicks. Instead, CORT chicks foraged with a greater number of flock mates and were less choosy with whom they foraged, resulting in more central network positions. These findings highlight the importance of taking developmental history into account to understand the drivers of social organization in gregarious species.
Highlights
Social network position is increasingly being linked to fitness
Zebra finches exposed to increased stress hormone levels during development (CORT chicks) foraged with more flock mates and more independently from their parents than control chicks, who were more ‘choosy’ with whom they foraged
This resulted in CORT chicks occupying consistently more central network positions than control chicks, by providing more ‘shortest paths’ between other birds
Summary
Social network position is increasingly being linked to fitness. The patterns of interactions between individuals form a social structure that can be captured using network analysis. Exposure to ‘stressful’ conditions in early development, such as intense sibling competition in large broods or food deprivation, can significantly increase endogenous levels of glucocorticoid hormones [5]. Experimental exposure to such stressful developmental conditions [6], or to elevated glucocorticoid hormone levels [7,8], has been shown to affect behaviours key to social interactions, such as competitive ability [7], mate choice [6] and social information use [8]. Individual variation in interaction rules can subsequently lead to different network positions, due to differences in attraction to conspecifics [9] or in the temporal maintenance of relationships [10]
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