Unlike humans and most land animals, dolphins cannot breathe through their mouths.
Dolphins are marine mammals.
However, they are different from most mammals because while land-dwelling mammals (such as humans) can eat and breathe through their mouth, dolphins breathe exclusively through their blowhole, located on the top of their head, and eat solely through their mouth.
While the exact reason for this difference is unknown, researchers and marine biologists have shared several possible views on why dolphins breathe differently from other mammals.
The dolphin’s lungs (air passage) and esophagus (food passage) are completely separated, which is extremely important to its survival.
When a dolphin dives underwater to capture prey, they need to be able to swallow their food without accidentally ingesting water into their lungs.
Dolphins can consume food underwater without drowning by having a breathing system separated from their throat.
Even if a dolphin tried to breathe through its mouth, it would be virtually impossible.
In addition to preventing dolphins from accidentally swallowing water while hunting for food, having a blowhole on the top of its head also makes it easy for dolphins to obtain oxygen near the water’s surface.
Having their blowhole on the top of their head, they can keep their body partly above the water without lifting their head, as a human or land mammal would need to do.
Dolphins can easily float at or near the water’s surface to take in oxygen during rest periods.
Information collected on these marine mammals using brain monitors shows that when a dolphin rests, only half of its brain shuts down while the other half remains conscious.
This likely allows the dolphin to quickly react to situations where it may be resting below the water’s surface so it can swim to the surface for fresh air when necessary.
It may also allow dolphins to react quickly to potential threats from predators or natural hazards.
One common misconception people have when they see a dolphin rise to the surface and spout water out is that it’s water that the dolphin took in through its mouth or nostrils. However, this is not the case.
The water that spouts from the dolphin’s blowhole surrounds the blowhole’s entrance while submerged.
As dolphins exhale with extreme force, it often causes the water surrounding the blowhole to shoot into the air.
If a dolphin tried to inhale the water, it would get into the dolphin’s lungs and possibly cause the dolphin to drown.
Before a dolphin gets ready to dive back underwater, it inhales a large amount of oxygen at a relatively quick speed, usually between 1 – 4 seconds, so it can quickly dive back underwater.
The muscles surrounding its blowhole contract when diving to prevent the dolphin from accidentally ingesting water when it descends.
The time a dolphin holds its breath underwater depends on the species.
Some dolphins have been recorded holding their breath for an average of 3 – 5 minutes, while others have been observed holding their breath for as long as 15 – 20 minutes.
Their diving length may be partially due to their hunting methods, as some species require deeper dives to find food.
It is also likely due to the physiological differences between certain species that are better able to handle long dives.