Largest whale's acrobatic ambush
Blue whales perform underwater acrobatics to attack their prey from below, scientists have found.
The massive mammals are known for lunge-feeding; gulping up to 100 tonnes of krill-filled water in less than 10 seconds.
Using suction cup tags, US researchers have recorded the surprising manoeuvrability of the giants.
They found that the whales roll 360 degrees in order to orientate themselves for a surprise attack.
The results are published in the Royal Society journal Biology Letters by Dr Jeremy Goldbogen and colleagues for the Cascadia Research Collective based in Washington, US.
"Despite being the largest animals to have ever lived, blue whales still show an impressive capacity to perform complex manoeuvres that are required to efficiently exploit patches of krill," said Dr Goldbogen.
The ways of whales
Blue whales feed exclusively on krill: small crustaceans that have excellent escape responses, requiring the mammals to have efficient foraging strategies to be able to meet their energy demands.
To understand how these giants manage to capture prey, despite their size reducing their mobility, Dr Goldbogen and his team tagged a group of animals off the coast of southern California, US.
Using suction cups to safely attach the acoustic recording tags without harming the animals, the team were able to track the whales' movements with the help of underwater microphones.
Results revealed that the whales were executing impressive spins below the waves in order to access large patches of krill.Tubular turns
"As the blue whale approaches the krill patch, the whale uses its flippers and flukes to spin 180 degrees so that the body and jaws are just beneath the krill patch," explained Dr Goldbogen.
"At about 180 degrees, the mouth just begins to open so that the blue whale can engulf the krill patch from below.
As the blue whale engulfs the prey-laden water, it continues to roll in the same direction and completes a full 360 roll and becomes horizontal again ready to target and attack the next krill patch."
The researchers were able to record video footage of the impressive acrobatics using a video camera worn by another animal to capture natural behaviour.
"We did not expect to see these types of manoeuvres in blue whales and it was truly extraordinary to discover," said Mr Goldbogen.
Previous research has identified similar behaviour in other rorqual whale species such as humpback whales, but these animals rarely exceed 150 degree turns.
In these smaller whale species the ability to twist and turn was attributed to long fins and tail flukes.
For blue whales however, scientists suggest the extra effort of turning rewards the massive mammals with enormous meals.
They also propose that the acrobatics optimise the animals' field of view.
"As in all cetaceans, [blue whales'] eyes are positioned laterally, and thus rolling the body should enhance panoramic vision in multiple dimensions," the study reported.
Dr Goldbogen commented that the results will fuel further research into the complex behaviour of whales, especially regarding predator-prey interactions.
"This extraordinary ability is only a glimpse into the diverse repertoire of manoeuvring behaviours performed by foraging animals," he told BBC Nature.
"Future tagging work has the potential to reveal many more unique insights into the daily lives of animals in their natural environment."