Blue whales are the largest-known mammals to ever exist, but the bulk of their diet is comprised of krill, teeny crustaceans that the whales gulp down by the ton. How do they get enough chow? As Ephrat Livni reports for Quartz, a new study suggests that blue whales maximize their feeding opportunities by occasionally performing powerful rolls to the left—even though most of them are “right-handed.”
A team of American and Swedish researchers used motion-sensing tags to track 63 whales off the coast of California. They analyzed 2,800 rolling lunges that the whales carried out while hunting, and found that most have right-side lateralization bias—or in other words, they favor their right side, just like many humans.
"Blue whales approach a patch of krill and turn on their sides,” study leader Ari Friedlaender explains in an Oregon State press release, adding that the majority of the whales’ hunting maneuvers involved 90-degree turns. “We found many of them exclusively rolled to their right, fewer rolled just to their left, and the rest exhibited a combination.”
The team wasn’t particularly surprised by this discovery. Plenty of animals have a right-side bias because in many vertebrates, the right eye is linked to the left side of the brain, which controls “coordination, predictive motor control and the ability to plan and coordinate actions,” according to the Oregon State press release. But researchers were surprised to learn that blue whales favor their left side when it comes to a single feeding strategy.
To hunt clusters of krill near the surface of the water, the blue whales rose from the ocean depths and flung themselves into 360-degree barrel rolls—and they nearly always rolled to the left, even if they typically favored their right sides. In a study published in the journal Current Biology, researchers attribute this behavior to the fact that krill patches at the ocean’s surface are smaller and less dense than they are further down. Rolling to the left, might let blue whales keep their right eye on sparsely distributed prey.
“[The blue whales] are trying to target these really small items of prey at the surface of the water and so they need to have some sort of predictive motor control,” study co-author James Herbert-Read explains in an interview with Nicola Davis of the Guardian. And predictive motor control is processed in the brain through the right eye.
The sort of selective ambidextrousness that the blue whales displayed has never been observed in animals before, according to the study authors. “I think it is just amazing,” Herbert-Read tells Davis, “that these are the largest animals that ever lived and we are still finding out these interesting and fascinating aspects of their behavior which we had no idea about.”