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Blue whale blow © Tim Stenton

How do whales and dolphins breathe?

Whales and dolphins are mammals and breathe air into their lungs, just like we do. They cannot breathe underwater like fish can as they do not have gills. They breathe through nostrils, called a blowhole, located right on top of their heads.

How do whales and dolphins breathe? WDC experts explain.

This allows them to take breaths by exposing just the top of their heads to the air while they are swimming or resting under the water. After each breath, the blowhole is sealed tightly by strong muscles that surround it, so that water cannot get into the whale or dolphin’s lungs.

Large whales have two blowholes (with the exception of the sperm whale) whereas dolphins have just one.

When a dolphin surfaces for air, he breathes out (exhales) first and then breathes in (inhales) fresh air; it only takes a fraction of a second for the dolphin to do this.  If you are close by, it is easy to hear a dolphin’s ‘blow’ at the surface; in fact you will often hear a dolphin before you see him!  The blow is the sound you hear, and the spray of water you see, when the dolphin forcefully breathes out and clears away any water resting on top of his blowhole.  The water spray is not coming from the dolphin’s lungs; it is just water sitting on top of its head around the blowhole being blown away before he inhales.

We exchange only about 10-15% of the air in our lungs with every breath, while whales exchange about 80 to 90%. They also have a very quick gas exchange. This short window of time at the surface also requires the whales to have extremely efficient breaths. This is possible because their lungs have a large surface area to rapidly exchange gases.

The most important way to get oxygen for these creatures is not through taking large breaths of air, but how they store oxygen molecules within their bodies. Oxygen is stored and transported around your body in your red blood cells in a protein called hemoglobin. Whales have twice the amount of hemoglobin in their blood that we do. So while your blood is 30% hemoglobin, a whale’s blood is 60% hemoglobin – allowing them to store twice as much oxygen for long dives. In addition to more hemoglobin, whales’ bodies have a higher percentage of blood – allowing even more oxygen storage.

Blood takes up 10-20% of a whale’s body volume, while our blood volume to body ratio is only around 7%. We also store oxygen directly in our muscle tissue in a protein called myoglobin. Whales’ myoglobin concentrations in their muscle are up to 30% higher than their terrestrial relatives. This molecule is distributed throughout the muscles in the body and holds up to 35% of whales’ oxygen stores. This is crucial as it’s important for oxygen to not only last as long as possible, but also be constantly supplied to the brain while they are underwater.

In order to conserve this precious oxygen, whales can do several things – one being that they have conscious control over their heart rate and can greatly reduce their cardiac output by slowing down their heart rate by over half. This reduces blood flow to non-essential organs (like skin and organs related to digestion) and some muscles because they have their own blood supply in the myoglobin. This is called ischemia. Additionally, blood pathways are shunted (or blocked) to certain tissues that are less important to the animal during dives—such as the stomach, while others sustain a steady blood flow- such as the brain. This process can be harmful to animals if prolonged which emphasizes the importance of rest periods.

Until recently it was thought that dolphins could not breathe through their mouths in the same way as people can, only through their blowholes. However, in 2016 scientists discovered a New Zealand dolphin with a damaged blowhole who had learnt to breathe through his or her mouth.

Dolphins are able to hold their breath for several minutes but typically they breathe about 4 or 5 times every minute.

Deep-diving whales such as sperm whales or Cuvier's beaked whales may go well over an hour between breathes. The record is held by a Cuvier's beaked whale that dived for 137 minutes (well over two hours!).

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