A drone footage of a blue whale feeding off the New Zealand Coast has been captured by researchers from the Oregon State University. The rare recording shows that the big mammals are picky eaters, and they won't consume the meal, unless its size is worth their effort.

On the video (see below), the big mammal is seen lunging towards a big patch of krill, roughly about its size. As it approaches its meal diligently, it turns on its side, pumps its flukes and increases its speed to about 6.7 miles per hour. On the other hand, another scenario shows the whale passing through a smaller patch of krill without feeding on it.

"Modeling studies of blue whales 'lunge-feeding' theorize that they will not put energy into feeding on low-reward prey patches," said lead researcher Leigh Torres, a principal investigator with the Marine Mammal Institute at Oregon State University, in a statement.

"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," Torres added.

As mentioned by Smithsonian Magazine, a blue whale can reach up to 100 feet and weigh up to 200 tons. In comparison, a male African elephant only weighs six tons.

With its behemoth size, it consumes a lot of energy when accelerating or slowing down. Simply opening its mouth to catch its prey can slow it down to 1.1 miles per hour; thereby, it has to be selective and has to consider the amount of krill it can catch in one lunge.

"The whale bypasses certain krill patches -- presumably because the nutritional payoff isn't sufficient -- and targets other krill patches that are more lucrative," Torres said.

The researchers think that the "picky" behavior of blue whales is due to energy conservation. Because of their size, stopping to lunge-feed and then speeding up again requires a high amount of energy. Therefore, they need to choose when to feed to maximize their energy.

According to Whalefacts.org, these giant sea creatures can consume as many as 40 million krill per day through filter-feeding.

World Wildlife Fund (WWF)
 noted that there are only about 10,000 to 25,000 blue whales globally, making them an endangered species. Climate change poses threat to its population, as warmer temperature may kill krill population, blue whale's top prey.