Even though blue whales don't have hands, or even feet, a new study has shown that most of them are in fact right-handed. This can be seen in the way that they feed. Interestingly, however, there's one particular situation in which they tend to go left instead.

Blue whales – the largest animal on the planet – feed by opening their mouths and lunging forward into water that's full of tiny crustaceans known as krill. They then strain the captured water out through sieve-like baleen plates in their mouths, leaving the krill inside to be swallowed.

Led by Ari Friedlaender, who is a researcher at UC Santa Cruz and Oregon State University, a team attached camera-equipped tags to the backs of 63 whales off the California coast, over the course of six years. Along with front- and rear-facing cameras, those tags also contained sensors that measured depth and movements in all directions.

When the footage and other data was analyzed, it was found that most blue whales usually roll about 90 degrees to the right as they're making their feeding lunge – the rolling motion likely relates to the biomechanics of opening the mouth. When they're lunging up toward krill patches located near the surface, however, they do full 360-degree rolls exclusively to the left.

The scientists believe that doing so allows them to keep their right eye facing toward the surface, where it can maintain a visual connection with the krill that they're after. As with other vertebrates, their right eye is connected to the left side of their brain, and vice-versa. Because the left brain predominantly controls the performance of routine actions, it's likely that the right eye provides more direct input to that control center.

If that's the case, though, why not roll to the left all the time? "At the surface, a krill patch will show as a nice counter-shade to the surface light," says Friedlaender. "At 200 meters or more, the whales can't see nearly as well." In other words, because their eyesight isn't as important when feeding at depth, their natural tendency to roll to the right takes over.

A paper on the study was recently published in the journal Current Biology.

Sources: UC Santa Cruz, Oregon State University