Drone video shows how blue whales eat: 'They try to maximize their effort'
“Modeling studies of blue whales ‘lunge-feeding’ theorize that they will not put energy into feeding on low-reward prey patches,” said Leigh Torres, a principal investigator with the Marine Mammal Institute at Oregon State, who led the expedition studying the blue whales. “Our footage shows this theory in action. We can see the whale making choices, which is really extraordinary because aerial observations of blue whales feeding on krill are rare.”
A blue whale needs to eat a lot; the creatures are sometimes the size of three school bus placed end to end.
But moving that massive body takes energy, too.
So blue whales don't just eat anything.
“The whale bypasses certain krill patches – presumably because the nutritional payoff isn’t sufficient – and targets other krill patches that are more lucrative. We think this is because blue whales are so big, and stopping to lunge-feed and then speeding up again is so energy-intensive, that they try to maximize their effort.”
Video captured in the Southern Ocean off New Zealand shows a blue whale approaching a mass of krill about the size of the whale itself.
"The animal then turns on its side, orients toward the beginning of the krill swarm, and proceeds along its axis through the entire patch, devouring nearly the entire krill mass," Oregon State said in a press release about the research. "In another vignette, the same whale approaches a smaller mass of krill, which lies more perpendicular to its approach, and blasts through it without feeding."
“We had theorized that blue whales make choices like this and the video makes it clear that they do use such a strategy,” explained Torres, who works out of Oregon State’s Hatfield Marine Science Center in Newport, Oregon. “It certainly appears that the whale determined that amount of krill to be gained, and the effort it would take to consume the meal wasn’t worth the effort of slowing down.
“It would be like me driving a car and braking every 100 yards, then accelerating again. Whales need to be choosy about when to apply the brakes to feed on a patch of krill.”
The video was captured with small drones.
“It’s hard to get good footage from a ship,” Torres said, “and planes or helicopters can be invasive because of their noise. The drone allows us to get new angles on the whales without bothering them.”