WASHINGTON, Nov. 20 (Xinhua) -- Just like humans, most blue whales show a right-side bias during prey capture, but a new study published Monday found that the world's largest animals shift directions and become "left-handed" when they swim into shallow water.
The findings, published in the U.S. journal Current Biology, offered the first evidence of "handedness" in blue whales, which can weigh as much as 25 elephants and extend over the length of a basketball court.
"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 Ari Friedlaender, a cetacean expert with the Marine Mammal Institute at Oregon State University who led the study.
"And we believe this left-sided rotation is a mechanism to help achieve that," said Friedlaender, who also is on the faculty of the University of California at Santa Cruz.
To support their hulking bodies, blue whales use various acrobatic maneuvers to scoop up many individually tiny prey, filtering the water back out through massive baleen plates in a behavior called lunge feeding.
In the new study, researchers attached motion-sensing tags to 63 blue whales living off the coast of California to capture how the animals move as they engulf their prey.
In total, the researchers collected data on more than 2,800 rolling lunges for prey to find that the animals approach their prey using two different rolling behaviors.
In some cases, they roll to the side and then back, turning 180 degrees or less. In other cases, they go in for a complete barrel roll that takes them around full circle.
They also found individual whales have a preference as to whether they roll to the right or the left.
The vast majority of the whales showed a preference for rolling to the right, much as more people show a preference for using their right hands.
However, when the animals did a barrel roll in shallow water to attack a small patch of prey from below at a steep angle, they more often spun left, going against their general preference.
"We believe that this left-side bias is the result of the whales maintaining a visual connection with their prey with their right eye," said Friedlaender.
"If the whales turned to the right on approach, they would lose sight of their prey and decrease the ability to forage successfully. By rolling to the left, the whales may be maintaining this visual connection to their prey."
"To the best of our knowledge, this is the first example where animals show different lateralized behaviors depending on the context of the task that is being performed," said study co-author James Herbert-Read from Stockholm University in Sweden.
The researchers said the next step is to conduct similar studies on related species of whales to understand whether the behaviors seen in blue whales also exist in them.
