Researchers have found that blue whales search and discriminate for the biggest and dense amount of krill to eat, so they can increase energy consumption. Contrary to the belief that they just ate without taken into account the distribution and the quantity of their food. The study was published in the Journal Science Advances on Friday.

Scientists tagged 14 blue whales and compared their foraging to 41 previously studied whales, in the coast of California. Also, scientists found that this aquatic mammals used an acoustic technique to measure the density of the groups of krill that they eat.

The southern tip of Sri Lanka is home to the world’s largest colony of resident blue whales. Tragically, one of the busiest international shipping lanes crosses the habitat of these endangered behemoths. This causes unnecessary and avoidable excess mortality that is likely to be hard to sustain for this population. Credit: MazdakTV

“For blue whales, one of our main questions has been: ‘How do they eat efficiently to support that massive body size?’ ” asked Elliott Hazen, a NOAA ecologist and lead author of the study, as reported in a press release. “Now we know that optimizing their feeding behavior is another specialization that makes the most of the food available.”

Whales swallow as much water as they can in one take, filtering the tiny krill included in the massive sip. Observing and looking for their best shot is their best way to maintain their huge weight and size without loosing too much energy.

Before they proceed to swallow the krill, they use a technique called “bubble netting” that consists in sending a fountain of bubbles from below the krill group so they get disoriented and easier to catch.

“Lunge-feeding is a unique form of ‘ram-feeding’ that involves acceleration to high speed and the engulfment of large volumes of prey-laden water, which they filter,” Jeremy Goldbogen, a marine biologist from Stanford University and co-author on the study, noted. “But we now know they don’t take in that water indiscriminately. They have a strategy that aims to focus feeding effort on the densest, highest-quality krill patches.”

A ball or swarm of krill – but imagine one that is several km or miles wide: in ideal conditions along the edge of the Antarctic ice sheet, they once got that big (

According to the Christian Science monitor, up to 2 million krill can swarm together but there are differences on their density and whales can tell. They save oxygen for the high density patches, making their ‘hunt’ effective.

“Blue whales don’t live in a world of excess and the decisions these animals make are critical to their survival,” said Ari Friedlaender, a principal investigator with the Marine Mammal Institute at Oregon State University’s Hatfield Marine Science Center and co-author on the study, according to EurekAlert.

Researchers believe this results will make a difference at the moment of protecting this endangered species. According to the IUCN Red List, between 10,000 and 25,000 blue whales still live on the planet, representing the 5 percent that lived before the rise of whaling industry.

Although further research has to be made, scientists think that their feeding modes are related to migration patterns, according to the Christian Science Monitor.

Source: EurekAlert