SYDNEY – Antarctic minke whales engage in an underwater feeding frenzy, filling their huge mouths up to 100 times an hour as they gorge on prawnlike krill during the summer, new research showed Friday.
The Australian Antarctic Division said it was the first time that the feeding behavior of the animals under the sea ice had been recorded, and the frenetic pace of the activity was unexpected.
“We were really surprised,” the division’s chief scientist, Nick Gales, said. “To actually see it and to see the incredible number (of lunges at food) and how cleverly they were able to use their behavior to exploit the krill under the sea ice was amazing to see.”
Like other baleen whales, minkes lunge forward with their mouths wide open to collect food, taking on a large volume of water which they then spill out as they trap the fish inside. While the huge blue whale will only do two or three such lunges during a dive for food, the smaller minke can do more than 20, sometimes at the rate of one every 30 seconds.
“It’s bloody hard work living down in Antarctica getting your prey, and these guys when they find their patch they work incredibly hard exploiting what prey is there,” Gales said. “This is by far the most frequent number of lunges in this sort of feeding that any baleen whale has ever been recorded to do.”
The recordings were made possible by satellite tags attached by Australian and American scientists to the animals off the west Antarctic Peninsula in 2013. The tags measured the orientation, depth and acceleration of the whales, Gales said, adding that the study also found that the minke’s length of nearly 9 meters gave them access under the ice to areas the larger blue whale could not reach.
“The minke’s preferred prey, Antarctic krill, aggregate under the sea ice and attract the whales to the area, leading to these feeding frenzies,” Gales added in a statement. “Any future change in sea ice has the potential to impact on the minke whales’ foraging habits.”
Gales said prior to the study, published in the Journal of Experimental Biology, the movements and diving behavior of these whales were a mystery. But the work exposed a successful strategy by which the animals could fatten during the southern hemisphere summer when there was a lot of food available to them in Antarctica.
“It’s a really, well, uniquely evolved strategy for getting krill, that’s why they are so successful. There are probably over half a million minke whales in all the oceans around Antarctica,” he said.
The study was part of the Australian-led Southern Ocean Research Partnership, which is endorsed by the International Whaling Commission.