Balancing care and conflict: towards a better understanding of maternal aggression in canaries (Dataset)

Parental care improves offspring quality and survival and hence enhances parental fitness, still seemingly maladaptive parental behaviours such as directed aggression and neglect have been reported for a variety of species. While maternal aggression may represent a behavioural pathology, it could also be an adaptive strategy enabling optimal resource allocation in the context of a trade-off between current and future reproduction and other evolutionary conflicts of interest. This study evaluated the functional consequences of maternal aggression for developing offspring in the domestic canary (Serinus canaria). We found that maternal aggression significantly impaired offspring growth, but it did not reduce their survival, thus it might have lasting negative effects on offspring quality. Additionally, early-life exposure to aggression resulted in increased threatening behaviours in juvenile male but not female offspring, which again suggests that understanding the significance of an aggressive parenting style may require incorporating long-term effects. Females exhibiting maternal aggression did not lay larger second clutches, as would have been expected if aggression relates to a trade-off between current and future reproduction. Still, they laid overall larger clutches that were less variable in size. This indicates that there might be phenotypic differences, with females behaving aggressively towards their offspring being less flexible and too optimistic at egg laying. Thus, despite having negative effects on offspring growth parental aggression could nevertheless represent an adaptive, context-dependent behavioural strategy.