Mothering influences domestic chick's laterality

Laterality is the prevalence of one side of the body to perform motor acts and perceptual functions. The evolution of directional biases that are consistent across individuals of a group may have been constrained by the opportunity for asymmetric animals to interact with other asymmetric animals. If we assume that social animals have more opportunity to interact with each other than solitary animals, we could expect that the more social animals are, the more lateralized and the more aligned they are. In precocial birds, the mother is the first and most important social partner and she has a strong influence on her offspring's social motivation. We therefore wondered whether she could also influence its laterality. To see whether mothering influences the chick's laterality, we compared behaviours of nonbrooded and brooded domestic chicks, Gallus gallus domesticus. We assessed both individual and group level laterality during the mothering period. We also measured sociality and emotivity of both types of chicks. We found that nonbrooded chicks were more strongly lateralized, more social and less emotional than brooded chicks. Asymmetrical bias was also more consistent across nonbrooded chicks than across brooded chicks. These results show a postnatal influence of mothering on the development of laterality in the domestic chick, and a link between laterality and sociality. Several hypotheses could explain how the mother's presence and behaviour can modify her offspring's laterality. We need to test these hypotheses to uncover the mechanisms that are at play. The influence of mothering on the lateralization of young may have implications in both individual and group performance and fitness. Studying it further may therefore help us to understand better the evolution of laterality and its potential benefits. (C) 2019 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.