Baleen whales—which include blue whales and humpbacks—are a type of whale that uses special filters instead of teeth to collect and eat small prey like krill and fish. Now, in a research first, scientists examining the consumption habits of these marine mammals have found they're ingesting millions of microplastic particles daily, which makes them the largest consumers on Earth of that type of waste. In a study published Tuesday in the Nature Communications journal, scientists recorded upward of 36,000 "lunge-feeding events" for 191 tagged baleen whales off the coast of California between 2010 and 2019 to gather their data, with drones deployed to monitor how much water was ingested with each lunge.
Using acoustic technology, researchers had already measured the prey's density in the water; they were also able to estimate the amount of microplastics in the prey found in each water column thanks to previous research. The researchers found that fish-devouring humpbacks are on the lower end of the range, sucking up a couple hundred thousand microplastic pieces per day. A "krill-obligate" blue whale, however, might take in 10 million microplastic bits daily, which could equate to upward of a billion pieces consumed over a three- to four-month feeding season, per the Guardian. If you placed that combined mass on a scale, its estimated weight would fall between 500 pounds and 4.5 tons.
Scientists determined that most of the microplastics—which CBS News describes as "tiny, synthetic polymers less than 5 millimeters long"—did indeed come from the whales' prey (ie, they're in the krill and fish), not from the water itself. And they note that baleen whales typically feed at 50 to 250 meters deep, which is where most microplastics are concentrated. The researchers believe their numbers are likely on the lower end, as plastic pollution has risen since they conducted their experiment, and that the issue is probably worse in other parts of the world where the oceans are more polluted. What comes next is figuring out how this plastic-eating regimen affects the whales. "This is the first step to figuring that out," says California State University-Fullerton's Shirel Kahane-Rapport, lead author of the study. (Read more whales stories.)