Eating isn’t easy for blue whales. To do so, they must maneuver their giant hulking bodies, which weigh as much as 25 elephants and are about as long as three school buses, to scoop up tiny krill, which they then filter through their mouths and swallow. Studies on whale dining techniques have found that they use a “rolling lunge” to catch their dinner and generally prefer to roll to the right — indicating “right-handedness” — but, as scientists report on Monday in Current Biology, certain instances will make them roll left.

Observations of 63 blue whales, described in detail in the paper, show that when they move into shallow water to dine, they unexpectedly switch things up with 360-degree barrel rolls that go to the left.

According to the international team of scientists that authored the study, this is the first evidence of “handedness” in blue whales and the first example of animals showing different lateralized behaviors depending on what task they need to do.

A great blue whale in the Indian ocean.

“These are the largest animals on the planet and feeding is an extraordinarily costly behavior that takes time, so being able to maximize the benefit of each feeding opportunity is critical,” said study leader and Oregon State University ecologist Ari Friedlaender, Ph.D., in a statement. “And we believe this left-sided rotation is a mechanism to help achieve that.” in a statement.

Friedlaender and his team used motion-sensing tags to track the movements of the 63 blue whales living off the coast of California and collected data on more than 2,800 of their rolling lunges. They found that for about 90 percent of the rolls, which normally occurred at 90 degrees to the side, the whales’ lateralization bias skewed right — which the scientists say support the idea that whales are “right-handed.”

This made sense to the scientists because most vertebrates have a right-hand bias. Because the left hemisphere of the brain controls the ability to plan and coordinate options, and the left side of the brain is linked with the right eye, an instinct to lead with the right emerges.

Most blue whales have the instinct to roll to the right. 

That made it all the more surprising to observe that, when blue whales to grab patches of krill closer to the ocean surface, they come in at a steep angle and perform 360-degree barrel rolls to the left — even the whales that normally have a preference for the right.

The scientists think that this bias toward the left in these situations is because these patches of krill are less dense than those in deeper water, so there is a greater need for the whales to keep their right eye on the krill. Because it’s such an effort for blue whales to eat, they can’t risk their shot.

“At the surface, a krill patch will show a nice counter-shade to the surface light,” Friedlaender explains. “At 200 meters or more, the whales can’t see nearly as well.”

Whales that can switch to the left are more common than humans who are truly ambidextrous, who only make up about one percent of the population.


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