To nourish their massive bodies, some of planet’s biggest whales use a technique called lunge feeding. In a dramatic display, the animals open their jaws nearly 90 degrees and gulp a mouthful of ocean water. Then, they push the water out of their mouth as their throat pouch deflates, trapping tiny fish and krill in their baleen. But until recently, scientists weren’t sure how lunge feeding whales performed the feat without choking on water.
The whales’ special feeding ability likely comes from a unique flap of muscle and fat found at the back of blue and fin whales’ mouths, according to new research published in Current Biology. The bulbous structure has never been described in any other animal before this, Sam Jones reports for the New York Times. The team of scientists who made the discovery suggests all lunge feeding whales—a family of baleen whales that includes species like humpback, fin and blue whales—may share this special throat plug to help them take in large meals.
“We have a lot of knowledge about that whole process of the mechanics of lunging and engulfing all that food, and that’s pretty much where the knowledge stops,” says study author Kelsey Gil, a marine biologist at the University of British Columbia in Vancouver, to Popular Science's Kate Baggaley. “We don’t know what’s going on in the throat.”
In their study, Gil and her researcher team examined the throats of 19 deceased blue and fin whales. They looked closely at the anatomy of the throat, carefully dissecting and manipulating various parts to see how they move, and also considered the direction of muscle fibers.
Here, a group of humpback whales lunge feed. Lunge feeding is when the whale lunges through a shoal of prey with its mouth gaping open, often breaking through the surface of the water. pic.twitter.com/1qVvjadAso— Oceana (@oceana) February 11, 2019
“When we had the mouth open in this fin whale, we saw there was this massive chunk of tissue at the back of the mouth completely plugging the pathway that the food has to take to get to the esophagus and the stomach,” Gil says to Popular Science.
Their dissections revealed an eight-inch-wide section of the soft palate that could shift to seal the upper airway. When the whales lunge feed, the "oral plug" blocks the channel between a whale’s mouth and its pharynx—the entrance to the respiratory and digestive tracts—so the animal doesn’t swallow or aspirate any water.
The flap is similar to a uvula in humans, which is pushed back when swallowing to prevent food or fluids from ending up in the space behind the nose.
“Think of [the plug] as a trapdoor,” says Gil to Sharon Oosthoek for Science News. “It’s always closed unless muscular activity pulls it out of the way.”
Lunge feeding allows these giant mammals to ingest thousands of pounds of tasty prey each day, which they need to maintain their semi truck–sized bodies.
“The more we can understand how they developed these means for being able to eat so much, and to be so efficient as foragers, the more we understand about what their capacities are, and how they function as part of marine ecosystems,” says Ari Friedlaender, who studies whale feeding behaviors at the University of California, Santa Cruz but was not involved in the recent study, to the Times. “It’s sort of the ultimate evolution of anatomy to be able to do these things that no other animals can do.”