It's no surprise that big whales are big eaters, but we may have underestimated just how much the largest varieties are actually consuming. According to new research, baleen whales—which include such species as humpbacks and blue whales—ingest three times more than we previously thought, with some able to take in up to 20 tons of food daily. "That amount of food is somewhere in the range of 20 to 50 million calories," says Stanford University's Matthew Savoca, the lead author of the study published in Nature, per NPR. "That is about [70,000] to 80,000 Big Macs. Probably decades of our eating is one day for them. So it's pretty remarkable."
It turns out past figures on how much these whales consume weren't gathered from studies of the big whales themselves but were estimated by extrapolating the number of calories taken in by smaller whales or by examining the remains of hunted whales' stomachs. Savoca and his team came up with a more precise solution: They tagged more than 300 baleen whales, comprised of seven different species, with special devices he calls "whale iPhones," equipped with GPS, cameras, and other gadgets to measure the size and density of nearby swarms of krill (the crustaceans that whales eat), as well as how many lunges into prey swarms the whales made daily, per National Geographic.
Drones helped measure the whales' mouth sizes so the scientists could guesstimate how much krill-filled water they took in with each gulp. Savoca says their feeding frenzy was almost unfathomable. "Blue whales might lunge into a prey patch 200 times a day," he tells NPR. "Humpback whales might do it 500 times a day." The study isn't just important for understanding the whales' eating habits—it's also crucial for understanding how much they poop. That's because whale excrement is high in iron, which spurs the growth of plankton, which is eaten by the krill, which are eaten by the whales.
Scientists say the insights gleaned into this nutrient-recycling system have also explained why krill is lacking in Antarctic waters: Baleen whales were almost wiped out there thanks to industrial whale-hunting in the 1900s, in what Savoca tells National Geographic was "one of the most effective and efficient extermination campaigns in Earth's history." Although other researchers say fishing and climate change have also played a part in keeping krill numbers down in polar waters, the study's authors say that "the recovery of baleen whales and their nutrient recycling services could augment productivity and restore ecosystem function lost during 20th-century whaling." (Read more whales stories.)