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

Abstract

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.

Testing the influence of habitat experienced during the natal phase on habitat selection later in life in Scandinavian wolves

“…In addition, females seemed to be more cautious than males. For instance, female orcas Orcinus orcas are particularly cautious when approaching humans 63 , and female Siberian flying squirrels occupy and move mostly in single, suitable patches of forest, whereas males, whose home ranges are larger, move around more fragmented terrain 64 . In Scandinavia, wolves, and especially females seemed to establish territories with habitat characteristics similar to those of their natal territories 19 .…”

History, development and current advances concerning the evolutionary roots of human right‐handedness and language: Brain lateralisation and manual laterality in non‐human primates

“…Cerebral and behavioural asymmetry at the population level, once assumed to be unique to humans, has been documented for all vertebrate classes (i.e., fish: Sovrano, Rainoldi, Bisazza, & Vallortigara, ; amphibians: Robins, Lippolis, Bisazza, Vallortigara, & Rogers, ; reptiles: Deckel, ; birds: Vallortigara, ; and mammals: Casperd & Dunbard, ; see also Rogers, Vallortigara, & Andrew, for a review) and several phyla of invertebrates (insects: Letzkus et al, ; arachnids: Heuts & Lambrechts, ; malacostracans: Takeuchi, Tobo, & Hori, , gastropods: Matsuo, Kawaguchi, Yamagishi, Amano, & Ito, ; cephalopods: Jozet‐Alves et al, ; and nematodes: Hobert, Johnston, & Chang, ; see also Frasnelli, ; Frasnelli, Vallortigara, & Rogers, for reviews). Cerebral and behavioural asymmetries have been described for various functions including motor control (e.g., limb laterality in birds: Brown & Magat, ; McGavin, ), sensory and cognitive functions (e.g., visual laterality in cetaceans:Chanvallon, Blois‐Heulin, Latour, & Lemasson, ; Thieltges, Lemasson, Kuczaj, Böye, & Blois‐Heulin, ) and communication (e.g., gestures in non‐human primates: Meguerditchian & Vauclair, ; Hopkins et al, ; Prieur, Pika, Barbu, & Blois‐Heulin, , 2016b). The apparent ubiquity of brain functional lateralisation in the animal kingdom would indicate that, in an evolutionary perspective, it would benefit biological fitness.…”

Orcas are social mammals

“…40 Indeed, adult orcas can be seen sleeping while the young calves continue swimming nearby. 47 There are many reasons behind this type of 'non-sleeping' among orca calves. One is that this could be a way of staying safe from potentially harmful predators while they are still young; after all, mortality rates are high amongst newborn orcas.…”