Effect of embryonic light exposure on laterality and sociality in quail chicks (Coturnix coturnix japonica)

Lateralization is the ascendency of one side of the body or the brain to control and perform motor or perceptual functions. Light exposure during prenatal life can modulate the expression of visual lateralization (strength and direction) in a variety of species, including birds. Individual lateralization provides cognitive advantages, but the function of lateralization at the population level is less obvious. Recent studies support the hypothesis that intraspecific population-level lateralization may favour coordination between asymmetrical individuals during synergistic (cooperative) social interactions. Since cohesion requires a good coordination, one can therefore imagine that a higher alignment of lateralization within a group, by making coordination between individuals easier, may promote social cohesion. Our study investigated the effect of light on laterality and social behaviour in Japanese quail chicks (Coturnix coturnix japonica). We compared chicks coming from eggs exposed to light during incubation to chicks coming from eggs maintained in complete darkness. We expected light-exposed (LE) chicks to be more aligned than dark-incubated (DI) ones and we wanted to test whether the most aligned chicks were also the most coordinated. We assessed laterality, social motivation, synchronization and spatial cohesion within groups of LE and DI chicks. The prenatal light conditions did not affect either laterality or chicks? social behaviour, and there was no turning bias at the group level. An absolute laterality index characterizing the alignment of chicks living together showed that the groups with the highest indices were not necessarily the groups with the greatest synchronization and spatial cohesion. This suggests that light does not consistently induce laterality in Japanese quail chicks and that the alignment of the chicks? turning bias does not influence their social cohesion. Quails are widely used in farm industry and scientific research and better knowledge of the consequences of incubation conditions on their behavioural asymmetries and sociality could help improve their handling and welfare.