Why Whales Don't Drown When They Eat

Watch a voracious whale go lunging after its prey in the water and it’s nearly incredible the whale doesn’t drown. 

Whales gulp down so many gallons of water as they swim at rapid speeds, grabbing mouthfuls of krill-filled water. Researchers have recently uncovered the anatomical secret that keeps the water from entering the whales’ lungs as they feed so quickly underwater.

Scientists were interested in lunge-feeding whales—including blue whale, fin, minke, and humpback—and how the respiratory tract is protected when swallowing. They already know a lot about the toothed whales including killer whales, sperm whales, dolphins, and porpoises and the anatomy of how the junction between the digestive and respiratory tracts works and what it looks like.

“But this was more of a mystery for lunge feeding baleen whales. We were aware of the anatomy of some structures in the throat, like the larynx, but weren’t exactly sure how they functioned to protect the respiratory tract,” lead author Kelsey Gil, a postdoctoral researcher in the department of zoology at the University of British Columbia in Vancouver, British Columbia, tells Treehugger.

“This was an important question for us to answer because maintaining protection of the respiratory tract during engulfment and during swallowing is necessary to allow lunge feeding, and lunge feeding is what enables these whales to grow so large.” 

When Lunge-Feeding Whales Eat

When a lunge-feeding whale spots prey in the water, it will accelerate to about 3 meters per second (10 feet/second), open its mouth to about 90 degrees, and take in so much prey-filled water that can be as big as the size of its own body.

“It then closes its mouth and pushes the water out through the baleen plates. The fringes on the inside of the baleen plates prevent any prey from being pushed out of the mouth with the water. The prey is then swallowed and another lunge occurs. For a fin whale, this procedure will happen about four times before the whale surfaces,” Gil says.

“When a whale lunge feeds it only engulfs so much water because that’s where the prey is— it isn’t trying to swallow all of that water. We don’t know how much water is actually swallowed along with the prey from each mouthful, but we assume it isn’t very much.”

To find out what bodily mechanics were allowing this to happen successfully, researchers examined deceased fin whales from a commercial whaling station in Iceland. They measured, took photographs, dissected certain areas, and analyzed the direction of the muscle tissue.

“Answering our question became a lot like putting pieces of a puzzle together—once we determined how one structure could move, we then had to determine how the surrounding structures would move in response to that,” Gil says.

“Looking at the direction of muscle fibres helps in this scenario, because it shows you what way a structure will move when that muscle contracts.”

Protective Anatomy

Researchers found that the whales had an “oral plug” that allowed food to pass to the esophagus while protecting the airways. The plug is a bulge of tissue that blocks the channel between the mouth and the pharynx.

Humans also have a pharynx region in the throat which is shared by both respiratory and digestive tracts. Both air and food pass through, but it’s not the same for whales.

When a whale is lunging for prey, the oral plug hangs from the back of the room of the mouth and rests at the top of the tongue. It’s held in place by muscles, which are pulled on as water enters the mouth, forcing them to tighten their hold on the plug.

“Once the water has been forced out of the mouth through the baleen plates the prey needs to be swallowed, which means the oral plug has to move to allow the prey to be transferred from the mouth, through the pharynx, to the esophagus and stomach,” says Gil.

“The only way this oral plug can move is backwards and upwards. When it does that, it shifts underneath the nasal cavities, blocking them off, so no prey accidentally goes up the whale's nose (towards the blowholes).”

To keep food or water from getting into the lung, cartilage closes the entrance to the larynx (voice box). With both the upper airways and lower airways sealed shut, the whale can then safely pass the prey into the esophagus. After the whale swallows, the oral plug relaxes and the whale can lunge again.

The findings were published in the journal Current Biology.

Researchers hope one day to study live whales, maybe by developing a whale-proof camera that could be safely swallowed by whales and then retrieved afterward.

And they want to find out more about whales’ bodily functions including whether they might actually burp during this process.

Gil says, “Humpback whales blow bubbles out of their mouth, but we aren’t exactly sure where the air is from—it might make more sense, and be safer, for whales to burp out of their blowholes.”