Extraordinary footage released by Oregon State University has revealed how blue whales off the coast of New Zealand pick and choose their meals.
Reasearchers say that the whales are so massive - sometimes growing to the length of three school buses - that they must carefully balance the energy gained through their food intake with the energetic costs of feeding.
The video, captured in the Southern Ocean off New Zealand, shows a blue whale cruising toward a large mass of krill - roughly 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.
"Modelling 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."
"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."
The rare footage was possible through the use of small drones. The OSU team is trained to fly them over whales and was able to view blue whales from a unique perspective.