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Largest Predator Performs Acrobatics to Feed

Blue whales, the world's largest predators, execute acrobatic 360-degree rolls when feeding on krill.
/ Source: Discovery Channel

Blue whales, the world's largest predators, execute acrobatic 360-degree rolls when feeding on krill.

Blue whales are now the only known rorqual whales (the largest group of baleen whales) that can complete a full circle roll. Other whales only go around 90-150 degrees, according to a study in the latest Royal Society Biology Letters.

Considering that blue whales grow close to 100 feet long and can weigh around 397,000 pounds, the feat is quite an achievement. The massive mammals manage the trick in two steps.

Lead author Jeremy Goldbogen told Discovery News that the first phase starts with an "180-degree roll prior to mouth opening, when the lunge occurs as the whale opens its mouth and engulfs the prey-laden water, which in this case is krill."

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For the second phase, there's "a further 180-degree roll in the same direction to complete the 360-degree spin. This maneuver is powered by several powerful fluke strokes and the tilting of the animal's flippers."

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."

"Nevertheless," he added, "krill exhibit well-known escape responses that do require, at times, the 360-degree rolling lunges observed here. In addition, blue whales have extremely large mouths that also limit krill's ability to escape and thereby maximize the amount of krill that can be captured in a single gulp."

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Frank Fish, a professor of biology at West Chester University, previously documented how alligators perform rolls during hunting and feeding and was impressed by the whale findings.

"It is remarkable that such a large animal can execute such a maneuver," he said. "They are not the inertial juggernauts that we think of them. Rather than only moving straight ahead without control, the whales can turn and orient the body to target whole schools of krill."

Goldbogen and his colleagues soon hope to estimate the energetic cost required for the blue whale's rolling move. It's also possible that different acrobatic maneuvers may be identified, thanks to technology that permits researchers to better glimpse the daily lives of whales.