Video: Rare drone footage shows why blue whales can be such picky eaters
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Blue whales are the largest creatures the planet has ever known, so it only makes sense they have an outsized appetite to match.
However, rare drone footage of the elusive creatures feeding off New Zealand proves they can be picky eaters when necessary, too.
In the video, the animals can be seen turning on their sides as they rapidly approach large masses of krill. Sometimes they dive in with mouths agape to scoop up their next meal. But other times, the whales make a late decision to bypass the drifting plankton.
Researchers say that’s because the whale’s immense size requires careful consideration about how much energy it can harvest from a mouthful of plankton versus how much energy is required to catch it.
“Modelling studies of blue whales lunge-feeding theorize that they will not put energy into feeding on low-reward prey patches,” said Leigh Torres of the Marine Mammal Institute at Oregon State University. "Our footage shows this theory in action. We can see the whales making choices.”
When the animal is cruising toward potential prey, opening its mouth slows it down considerably. That loss of momentum means the whale must exhaust a huge amount of energy to get back up to speed.
“It would be like me driving a car and braking every 100 years, then accelerating again,” Torres said. “Whales need to be choosy about when to apply the brakes to feed on a patch of krill.”
Torres added the footage would have been impossible to obtain without the use of small drones, since the noise of a helicopter or airplane would disturb the whales.
Blue whales are estimated to grow as long as 30 metres in length and weigh as much as 181 tonnes on a diet that overwhelmingly relies on krill. They are considered an endangered species and a recent study estimated the global population is between 10,000 and 25,000.
In 2014, nine blue whales were killed when they became trapped in pack ice off Newfoundland. One of them, a 28-metre female, was stripped down to her bones and the skeleton was shipped to Toronto where it is now on display at the Royal Ontario Museum.