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Animals

Study reveals why whales can take such big gulps without choking

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A fin whale. (Photo by Finhval via Wikimedia Commons)

By Tom Campbell via SWNS

Whales have an "oral plug" so they can take big gulps of water as they eat without choking, reveals a new study.

Fin whales, also known as rorquals, can block the back of their throats while lunging through the water with their mouths wide open, say scientists.

They take massive gulps to capture small prey like krill or plankton suspended in the water before filtering and swallowing them.

While this feeding behavior has been well documented, less attention has been paid to what happens once their mouth is full of seawater.

Now researchers have found fin whales have an 'oral barrier' which protects seals off the back of their throats - or pharynx.

This type of blockade has not been observed in any other animal species.

Dr. Kelsey Gil at the University of British Columbia in Canada said: "We discovered a structure in fin whales, which likely exists in all lunge-feeding whales or rorquals.

"We’ve termed it the ‘oral plug’ and found that it blocks the channel between mouth and pharynx.

"It means that when a whale lunges, the entrance to the pharynx and thus the respiratory tract is protected.”

A hollow organ that forms an air passage to the lungs and holds the whale's vocal cords known as the larynx has also been closely studied.

But little is known about the rest of the pharynx - or throat, in particular the junction between respiratory and digestive tracts.

Dr. Gil said: “It’s impossible to study this in a living whale, so we rely on tissue from deceased whales and use functional morphology to assess the relationship between a structure and its function."

The researchers examined the whales' anatomy and dissected their pharynx before manipulating its various parts to see how they moved.

They also looked at the direction of muscle fibers to determine how they moved if they were flexed or loosened.

A fin whale. (Photo by  Fin Whale via Wikimedia Commons)

Dr. Gil said: “The oral plug is a part of the soft palate, so simply considering the gross anatomy, there is only one direction it should move.

“When the oral plug moves backward and upward to block the nasal cavities, it means that no other structure can be in that same spot below the nasal cavities."

The larynx's positing was compared while the giant mammals were breathing and swallowing their prey.

When it swallows, a muscular sack attached to the bottom of the larynx is forced upwards to completely block the whale's lower respiratory tract, the researchers found.

In fin whales, found in deep waters of all major oceans, the pharynx could only be used to breathe or swallow, but not both at once.

No structure like the oral plug has been reported in any other animal species, which suggests it could be unique to whales.

Dr. Gil said: “There are very few animals with lungs that feed by engulfing prey and water, so the oral plug is likely a protective structure specific to rorquals that is necessary to enable lunge feeding."

The researchers are planning to continue studying the rorquals' pharynx and respiratory and digestive tracts in more detail as they believe there could be many more unknown features about these whales.

The findings were published in the journal Current Biology.

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