Whale feeding manoeuvre captured in footage

By Paul Harper

Researchers have captured never-seen-before footage of blue whales performing 360-degree rolling manoeuvres to gulp mouthfuls of krill.

Dr Jeremy Goldbogen and colleagues from the Cascadia Research Collective in Washington, in the United States, used suction pads to attach multi-sensor tags to blue whales to record their foraging in the waters off southern California.

The researchers were surprised to find the large mammals spin to capture krill during their lunges.

"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," Dr Goldbogen told BBC Nature.

"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."

Kinematic analysis revealed 44 manoeuvres were performed by 11 out of 22 tagged whales.

Footage of the phenomenon was also captured by a camera attached to one of the whales.

In 10 seconds the whales can haul in up to 100 tonnes of krill-filled water during its lunges.

The findings have been published in Biology Letters.

Other rorqual whale species such as humpback whales do use rolling techniques to capture prey, but the blue whale is the only one known to roll a full 360 degrees.

The whales make the impressive manoeuvres despite its large size - blue whales can grow to about 30-metres in length - and its relatively small flippers and flukes that limit its manoeuvrability.

The researchers suggest the whale is rewarded for the extra effort required to perform the ambush manoeuvre with a much large haul of food.

"Given that some krill patches can be extremely dense, a blue whale may be able to meet its daily energetic demands in only one foraging dive," the researchers wrote.

"Thus, for a high-quality krill patch that is difficult to attack, blue whales may be motivated to perform these extraordinary acrobatic manoeuvres in order to maximise foraging efficiency. Without the manoeuvre, blue whales could miss the krill patch completely, resulting in the mismanagement of limited dive time and a decrease in foraging efficiency."

The whales in the study only perform the roll during only 10 percent of its lunges, leading the researchers to suggest it may be a honed strategy specific for a certain prey patch shape or size.

The roll was only performed during foraging, the researchers said.

- NZ Herald

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