Blue whales perform 360 degree somersaults to catch more krill, video shows (Wiki commons)
Blue whales, the world's largest animal, perform acrobatics underwater while feeding in order to catch more krill - their staple diet.
The whales, which grow to 30 metres (100ft) in length and weigh 180 tonnes, perform 360 degree somersaults to ambush their prey from below.
A study published by the journal of the Royal Society measured the foraging behaviour of blue whales. Analysis of the high-resolution digital acoustic recording tags attached to the animals showed them performing rolling lunge manoeuvres.
Blue whales feed by engulfing large amounts of prey-laden water in one big gulp. The effectiveness of this method obviously depends on how much prey is in the water.
The study showed that blue whales perform acrobatics in order to position their lower jaws better so the krill can be swallowed while the whale's body is inverted.
It says: "Theoretical models indicate that this rolling behaviour is aimed at anticipating the prey's escape trajectory, such that the jaws are repositioned to where krill will be at the time of mouth opening, and thus maximises prey capture."
Somersaults also allow whales to see the prey, therefore increasing hunting efficiency by working out where the krill patch is at its densest.
Scientists recorded 44 somersaults in 11 out of 22 tagged blue whales. "Within this context, and the fact that only 10 percent of lunges in this study involved a 360 degree roll, this behaviour may represent a honed strategy that is specific for a certain prey patch shape or size," the study said.
"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.
"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 maximize 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.
Previously, other species of whale have displayed rolling behaviours, including fin and humpback whales. However, the magnitude of the rolls of these species is normally up to 90 degrees and does not exceed 150 degrees.