Postnatal care generates phenotypic behavioural correlations in the Japanese quail

Abstract: Behavioural phenotypes can be highly constrained by interdependent behavioural traits. Studies in different taxa showed that these behavioural phenotypic correlations are not universal within a species and can differ between populations exposed to different environmental pressures. Empirical studies are required to better understand the relative contributions of long-term adaptive processes and direct ontogenetic mechanisms in the development of these phenotypic behavioural correlations. In the present study, we investigated the role of postnatal nurturing care on the development of behavioural correlations in a precocial bird model, the Japanese quail (Coturnix coturnix japonica). We compared phenotypic correlations between two populations: 41 artificially reared birds (maternally deprived) and 36 birds fostered by unrelated females. Behavioural responses were measured at the age when birds naturally disperse, with three widely used behavioural tests to assess fearfulness and sociality: tonic immobility, open-field and emergence tests. Our results show that when quail chicks are reared by a foster mother, more phenotypic correlations appeared in the population including correlations within and across behavioural functions and between behavioural responses and chick mass. In contrast, chicks reared without a foster mother presented much fewer behavioural correlations and those were limited to functionally linked behaviours. Our results also highlight that the effect of mothering on phenotypic correlations is sex-specific, with a greater effect on males. We discuss the organisational role of parents on the development of behavioural correlations, the mechanisms likely to support this influence, as well as the reasons for sexual dimorphism. Significance statement: Mothers deeply influence the behavioural development of their offspring during the postnatal stage. Whether maternal presence and nurturing behaviour also affect correlations between behavioural responses of their offspring at a population level remains underexplored and unclear. In the current study, we used an adoption procedure to demonstrate the critical role of maternal postnatal care for the development of behavioural correlations in a precocial bird model widely used for the study of behavioural ontogeny: the Japanese quail. Our findings highlight that the presence of a maternally behaving female during early life promotes the development of correlations between behavioural responses both within and across behavioural functions in males but not in females.