In a significant majority of pairs, the following bird viewed the leading partner with the left eye during routine behaviours such as resting and feeding in undisturbed conditions.

In geese flocks, we recorded which visual hemifield (left/right) the following partner used to monitor the leading partner relevant to the type of behaviour and the disturbance factors. The male-female pairs of two geese species (barnacle, Branta leucopsis, and white-fronted, Anser albifrons geese), were observed during different stages of the annual cycle in a variety of conditions. In the present study, we investigated lateralized spatial interactions between the partners in lifelong monogamous pairs. However, there are few studies focused on the lateralization in cooperative behaviours of individuals, especially in a natural setting. The potential role of lateralization in oval squid is discussed.Д«ehavioural lateralization, which reflects the functional specializations of the two brain hemispheres, is assumed to play an important role in cooperative intraspecific interactions. The volume of the right optic lobe gradually became larger than the left lobe during the schooling period, although this was not correlated with behavioural lateralization. The strength of eye use, regardless of the direction, appeared at the population level in both the solitary and the group conditions during all life stages. In the period before school formation, the right eye was used for detecting conspecifics in the solitary condition, while in the group condition, the right eye was used for detecting predators and conspecifics. The right eye was used at a population level for detecting specific targets during the preschooling period, while no trend was detected in both the solitary and group conditions during the schooling period. We found that eye use and optic lobe lateralization in oval squid changed with the development of schooling behaviour.

Optic lobe lateralization was examined by estimating the left and right optic lobe volumes using microcomputed tomography. Behavioural lateralization was tested by observing which eye solitary and group individuals used to detect prey, predators and conspecifics. In this study, we investigated ontogenetic changes in the lateralization of oval squid, Sepioteuthis lessoniana, by observing their behaviour and the brain region, that is, the optic lobes, that process visual information.

Lateralization has been observed in coleoid cephalopods (squid, cuttlefish and octopus) which possess sophisticated lens eyes and a large brain, the largest among invertebrates. Lateralization is expressed at individual and population levels (most individuals in a group are lateralized in the same direction) and switches during ontogeny. Lateralization appears as a leftвЂ“right asymmetry of morphology and behaviour in many animal species including both vertebrates and invertebrates and provides functional advantages for survival. We hypothesize that the increased demands for right hemisphere processing to deal with stressful and emergency situations may interfere with the manifestation of lateralization in social interactions. In contrast, no significant bias was found in a variety of geese behaviours associated with enhanced disturbance (when alert on water, flying or fleeing away when disturbed, feeding during the hunting period, in urban area feeding and during moulting).

This behavioural lateralization, implicating the right hemisphere processing, was consistent across the different aggregation sites and years of the study. In the present study, we investigated lateralized spatial interactions between the partners in life-long monogamous pairs. Behavioural lateralization, which reflects the functional specializations of the two brain hemispheres, is assumed to play an important role in cooperative intraspecific interactions.

Flock of geese