Social influences during adolescence on adult behaviour in zebra finches: endocrine mechanisms and functional consequences

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Adolescence is the key life history stage during which an individual reaches sexual maturity and becomes independent from its parents. Studies on mammals show that the social environment during this transitional period can have life-long consequences for the way in which individuals cope with social and other challenges as adults. During the past years, we investigated whether the social environment during adolescence is of similar importance for adult behaviour of birds. Male zebra finches growing up with a single female during adolescence showed more courtship and aggressive behaviour and were initially more attractive than group-reared males (3 males and 3 females). Four months later, the differences in courtship and aggressiveness persisted, albeit slightly diminished, but the males no longer differed in attractiveness. Since costs and benefits of courtship and competitive behaviour depend on the social context, these effects may represent adaptive behavioural responses to the social environment due to their experiences during adolescence. Our observations resemble earlier findings in guinea pigs suggesting a general phenomenon not restricted to mammals with potentially also similar underlying mechanisms and adaptive function. The key objective of the current proposal is therefore to study the mechanisms and the adaptive value of the long-term effects of social experiences during adolescence. First, we will describe in more detail the hormonal profiles and behaviour while individuals are kept during adolescence in different social environments and the subsequent consequences of these changes for behavioural and hormonal response when encountering a potential mate, competitor or a physical stressor (immobilisation). We will then study the functional consequences of the observed long-term effects on courtship and aggressiveness by assessing (correlates of) fitness costs and benefits in different social settings during adulthood. Using hormonal manipulations (blocking receptors and manipulating hormones during early development and adult life) we fill experimentally test whether the suggested hormonal mechanisms can indeed explain the observed long-term effects on behaviour.