Goldbogen, a postdoctoral researcher at Cascadia Research Collective, and his colleagues discovered the move after attaching suction cup multi-sensor tags to blue whales foraging in the waters off of southern California. The researchers recorded the full circle move not only when whales were feeding, but also when the marine mammals were in a searching mode between lunges.
"We think that this behavior improves the whale's chances of engulfing the most amount of krill possible," Goldbogen said.
He explained that because of their enormous size, blue whales can be easily detected by krill (and probably almost anything else in the ocean). If they attack krill from below, however, they might be able to avoid being seen.
"So essentially, the whales spin over and engulf the krill patch while inverted, from below," he said, adding that it's an "ambush strategy."
Strangely enough, the blue whale's huge size could help to explain why it primarily eats tiny krill.
"We have speculated that blue whales rely only on krill because of the blue whale's extreme size and limited maneuverability," Goldbogen explained. "This results in the blue whale being less efficient at exploiting more maneuverable prey species, such as fish."