Right-Finned? Left-Finned? Finned dominance in Orcas!

Humans and many other organism are known to display handedness and have a dominant brain hemisphere, a behavior that is often a topic in pop-culture. In recent years, a similar idea has been suggested to be found in cetaceans through a behavior called lateralization. Lateralization is when there is a tendency for cognitive processes and functions to be more dominant in one hemisphere of the brain over the other, according to Psychology Today. In cetaceans, the behavior of lateralization seems to be expressed through a side dominance when landing from lunges. When lunging – a common behavior characterized by whales breaking the water while in pursuit – cetaceans are found to have a side preference where they will land on either their right or left side depending on the species (Karenina et al, 2015). According to previous studies done, Striped Dolphins (Stenella coeruleoalba) and Humpback Whales (Megaptera novaeangliae) prefer to land on their right side, while Beluga Whales (Delphinapterus leucas) prefer their left side. Unlike humans, however, the biases appear at a species level rather than an individual level and have been found to change with different behaviors.

A study done by four scientists, Karina Karenina, Andrey Gijov, Tatiana Ivkovich, and Yeghor Malashichev, focused primarily on Killer Whales’ (Orcinius orca) side-preferences in light of their comparative differences between lunging during foraging and breaching. There have been numerous studies concerning lateralization in cetaceans, however this topic is still widely debated. The Killer Whale study done was not an experiment to support any side of the debate, rather it was an observational study that researchers were able to find correlations through. This study focused on describing lateralization in surface behavior of resident orcas through side bias in lunging during both foraging and breaching and determining what side preference there was.

The researchers defined lunging, foraging, and breaching to properly observe and record the behavior of their subjects. Lunging is described as the individual breaking the water with its rostrum, or top part of its body, in a pursuit. Lunging generally ends with the whale landing on its side, which is the bias being studied (Karenina et al, 2015). This behavior was observed during foraging – a pursuit for food – and during breaching – a behavior that has communicative purposes. Data was collected during the summer in Avacha Gulf on resident orcas. Observations were made over the course of nine years from 2005 to 2014. The whales were approached using small boats and the scientists were careful to prevent disturbing any behavior. In total, there were sixty individual lunges recorded, each from a different subject observed. Of the lunges recorded, 75% of them were found to be on the right side, showing a right-side bias in lunging during foraging. In breaching events, there was no side preference found.

The results of this study show a correlation between right-side lunging in foraging, but no side-bias in lunging while breaching. In previous studies, there is a significant correlation of right-sided preferences in toothed and baleen whales. These observations support the theory that right-biased feeding in marine mammals is consistent of behavioral lateralization. The results also help us better understand the neurological aspects of foraging and breaching behavior in orcas, as well as observing another species that displays a version of handedness.

Sources:

• Karenina, K., Gijov, A., Ivkovich, T., & Malashichev, Y. (2015). Evidence for the perceptual origin of right-sided feeding biases in cetaceans. Animal Cognition, 239-243. Retrieved October 8, 2017.
• Furnham, A. (2017, January 10). Breaking Up is Hard to Do: the Right and Left Brain. Retrieved October 09, 2017, from https://www.psychologytoday.com/blog/sideways-view/201701/breaking-is-hard-do-the-right-and-left-brain