Spontaneous approaches of divers by free-ranging orcas (Orcinus orca): age- and sex-differences in exploratory behaviours and visual laterality

• Published in: Scientific Reports
• Main Authors: Chanvallon, Stéphanie, Blois-Heulin, Catherine, Robert de Latour, Pierre, Lemasson, Alban
• Format: Text
• Language: English
• Published: Nature Publishing Group UK 2017
• Subjects: Article; Orca; Orcinus orca
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5589820/; http://www.ncbi.nlm.nih.gov/pubmed/28883537; https://doi.org/10.1038/s41598-017-11488-3

Running comparative studies of laterality in mammals is a way to deepen our understanding of the evolution of the brain hemisphere functions. Studies on vision highlighted a possible task-sharing between hemispheres depending on the characteristics of the observers, the nature of the observed stimulus and the context of the observation, a phenomenon that could go beyond the monitoring of conspecifics. Cetaceans are predators that adapted to an aquatic habitat and display a clear crossing of fibers to the side of the brain opposite the eye of origin. Here, we analysed the interactions between humans and cetaceans when free-ranging orcas approach divers. Our study concentrated on the spontaneous exploratory behaviours of divers by orcas depending on their age and sex, and on the possible expression of a visual laterality. The results showed a significant preference for the use of the left eye but exclusively in adult females. Adult males had a more sustained attention than adult females, marked by a higher spatial proximity to divers, slower approaches and longer look durations. Adult females, probably more cautious, explored from the distance and more furtively. Our findings support a possible link between attentional/motivational states and visual laterality in mammals.