Why don’t whales drown when they eat?

If you’ve ever seen a lunge-feeding whale, you might have wondered why the animal didn’t drown while gulping down those massive amounts of water and krill.

Well, researchers have found that these whales have a nifty ‘oral plug’ to thank for staying alive. This fleshy bulb in the whale’s mouth moves backwards while feeding to seal off its upper airways, while the larynx closes to block the lower ones.

The plug prevents water from entering the lungs, which is useful when feeding involves lunging at prey, accelerating at high speed and opening you mouth to engulf both water and krill.

According to lead author Dr Kelsey Gil, a researcher at the University of British Columbia (UCB), Canada, the volume of water engulfed can sometimes be even larger than the whales’ own bodies. It’s an impressive feat when you remember that this group includes humpbacks and the largest animal on Earth – the blue whale.

“We haven’t seen this protective mechanism in any other animals, or in the literature,” says Gil. “A lot of our knowledge about whales and dolphins comes from toothed whales, which have completely separated respiratory tracts, so similar assumptions have been made about lunge-feeding whales.”

Investigating fin whales specifically, the team found that the oral plug needed to move so that the tiny krill – left behind after the water drained through the whales’ baleen – could pass to the oesophagus.

The oral plug moves to the back of the head and up (blocking nasal passages), while cartilage closes at the entrance to the larynx simultaneously and the laryngeal sac moves up to block the lower airways.

You probably haven’t taken any notice while eating, but it turns out that humans have a similar method of swallowing food without letting it get into our lungs.

“It’s kind of like when a human’s uvula moves backwards to block our nasal passages, and our windpipe closes up while swallowing food,” says Gil.

Humans could probably eat underwater as well, according to Gil, but if doing it like the whales, it would be rather like swimming at high speed towards a hamburger and opening your mouth wide as you approached – difficult not to flood your lungs.

Importantly, these findings indicate that the plug and closing larynx are central to how lunge-feeding evolved, and thus to how these enormous creatures can grow to such sizes.

“Bulk filter-feeding on krill swarms is highly efficient and the only way to provide the massive amount of energy needed to support such large body size,” says senior author Dr Robert Shadwick of UCB. “This would not be possible without the special anatomical features we have described.”

Since investigating whales’ anatomy often involves trying to quickly dissect beached whales before the tide rises, the researchers instead used recovered tissue that wasn’t being used for food from a commercial whaling station.

And although working with live whales in real time would be wonderful, Gil says it might require some advancements in technology first.

“It would be interesting to throw a tiny camera down a whale’s mouth while it was feeding to see what’s happening, but we’d need to make sure it was safe to eat, and biodegradable.”

She says there’s still plenty more to find out about whales, including whether they cough, hiccup and even burp.

“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,” she says.