We finally know why whales don’t drown when they swallow krill

Baleen whales are heavy drinkers. In just ten seconds, these giant mammals can descend more than five hundred seawater baths, filtering about 10 kilograms of krill in a single sip.

All they have to do is open their mouths and roughly rush 10 kilometers per hour (6 miles per hour).

The pressure of all that water rapidly hitting a whale’s throat would surely be immense. So how does this group of creatures – which includes right whales, humpback whales and the monumental blue whale, among several others – ensure that their lungs aren’t suddenly flooded with water?

The dissection of several fin whales (Balaenoptera physalus) has now revealed a fatty, muscular sac that prevents the species from choking. When the whale opens its mouth to feed, this sac swings upwards and clogs the lower airways.

No such structure has ever been identified in any other animal, but the authors suspect it is likely present in other slot-feeding whales (called fin whales), such as humpback and blue whales. .

“There are very few animals with lungs that feed by engulfing prey and water, so the mouth plug is likely a rorqual-specific protective structure that is needed to enable cleft feeding,” says zoologist Kelsey Gil from the University of British Columbia, Canada.

Although Gil and his colleagues haven’t seen the oral plug in action, based on its structure, they believe it works much like a railroad switch. When a whale breathes, the plug comes out and opens the lower airways. But when a whale feeds, the plug completely blocks that pathway.

In humans, a flap of tissue known as the epiglottis covers the way to the lungs when we eat so we don’t accidentally inhale our food.

But whales have very different ways of eating and breathing. When they breathe through their blowholes, the fatty plug attached to the soft palate prevents water from the mouth from flowing into the lungs.

When they eat, however, this fatty plug must swing up and back, closing the way to the whale’s upper blowhole, while opening the esophagus to swallow it.

Meanwhile, the sheer force of the incoming water pushes the whale’s tongue against the epiglottis, also sealing off the lower airways.

Swallowing versus breathing in fin whales. (Alex Boersma/Current Biology)

“It’s kind of like when a human’s uvula moves back to block our nasal passages and our trachea closes when swallowing food,” said Gil.

But unlike the structures of the throat in humans, those of whales have to work under great pressure.

“Bulk filter feeding of krill swarms is very efficient and the only way to provide the huge amount of energy needed to support such body size,” Explain zoologist Robert Shadwick, also of the University of British Columbia.

“It would not be possible without the particular anatomical features that we have described.”

After all, it takes a lot of energy for a Fin whale 27 meters long keep swimming.

There is still so much to learn about these giant creatures and their lives under the waves. For example, how do whales blow bubbles? And do they burp or hiccup?

The authors of the current study would like to watch a baleen whale eat and breathe in real time; to do this, they would need to create an avalable camera.

In the meantime, the dissections were not performed on whales captured for scientific purposes, but performed on specimens acquired during a commercial whaling operation in Iceland in 2015 and 2018, where fin whales have luckily not killed during the last years.

The study was published in Current biology.

Comments are closed.