Ambidextrous behaviour by "right-flippered" blue whales has surprised scientists studying the huge creatures' feeding habits.
Like many other animals, ranging from primates to insects, blue whales display laterality, or "handedness" - generally a bias towards the right.
But a unique study using video cameras attached to the backs of the mighty cetaceans has shown how the whales switch laterality when feeding.
Blue whales, which weigh as much as 25 elephants and are the largest animals ever to have lived on Earth, are famous for their dramatic "lunge feeding" acrobatics close to the ocean surface.
As they launch themselves upwards into swarms of the tiny crustaceans, called krill, on which they feed, the whales execute 360 degree barrel rolls. And according to the video evidence, they almost always roll to the left.
This is in marked contrast to the way they normally feed at greater depths, when they execute 90-degree right-handed side rolls.
US lead researcher Dr Ari Friedlaender, a cetacean expert at Oregon State University's Marine Mammal Institute, said: "The patches of prey near the surface are usually smaller and less dense than prey patches found deeper and the blue whales showed a bias toward rolling left - presumably so they can keep their right eye on the prey patch and maximise their effort.
"We were completely surprised by these findings, but when considering the means by which the whales attack smaller prey patches, the behaviour really seems to be effective, efficient, and in line with the mechanisms that drive their routine foraging behaviours."
It was the first known example of an animal altering handedness to adjust to the context of a performed task, said the scientists writing in the journal Current Biology.