Are whales righties or lefties?

For species that are more accustomed to feeding in the water column, we can determine whether they favour one side by observing their turns. In toothed whales, laterality is visibly present. In the Bahamas, the common bottlenose dolphin seems to adopt a consistent directional movement during its foraging activities. Indeed, before diving to feed in the craters, it seems to prefer to turn to the left 99% of the time.

The same goes for the finless porpoise in Japan, which also spins counter-clockwise, with the right side facing downward, when hunting fish near the water surface.

Surprisingly, blue whales seem to favour different orientations depending on what they are doing. A study that analyzed their behaviour using motion sensors reveals that the majority of blue whales turn to the right when hunting in deep water. However, when these whales ascend to hunt prey at shallower depths, they complete a 360-degree rolling manoeuvre to the left.

In the case of toothed whales, lateralized behaviour might also be attributable to other factors such as echolocation. Indeed, toothed whales are believed to better perceive echolocation signals coming from the right, which might also explain some of their directional movements.

Lateralization behaviours observed in whales – which amongst other things allows them to maintain visual contact with their prey thanks to a dominant eye – often aim to optimize foraging and predator defence strategies. Is the preference for one side of the body over another hereditary? Or is this a behaviour acquired by mimicking the gestures of the parents? Scientists don’t yet have the answer to these questions.