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How Do Mammals Breathe?

I remember learning about how humans breathe at school and wanted to write this article.

All mammals use a pair of lungs for breathing oxygen. All mammals need oxygen to survive, which is contained in the air. Marine mammals breathe air at the surface of the water. The sperm whale can hold their breath the longest, allowing them to dive for up to 90 minutes. 

There are around 4500 species of mammals globally, with approximately 457 mammals living in the continent of North America.  Mammals have different breathing practices and ways of breathing using their lungs. To learn more about how mammals both on land and in the sea breathe, please read on.

Do All Mammals Have Lungs?

One of the crucial characteristics of mammals is that they breathe air oxygen using their lungs. All mammals have lungs, including those living in the sea.

Lungs are used to inhale fresh air filled with oxygen to fuel the mammals’ body.  This air exhaled is filled with carbon dioxide. 

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Though lungs come in different sizes and shapes for various mammals, all mammals have lungs, which are crucial for breathing. Whales, dolphins, and other underwater mammals have lungs as their breathing organ and not gills, which fish possess.

Despite having the same use, the lungs of different kinds of mammals work differently and are designed to survive in their particular environment. 

Seals have lungs, which help them to stay underwater for long periods.  Predatory mammals like wolves or jaguars have lungs that help their stamina to run long distances to chase prey.  Bats have lungs designed to help them fly efficiently.

Do All Mammals Breathe Through Lungs?

All mammals breathe through their lungs. No matter how big or small the mammal is, they always use their lungs to inhale oxygen and exhale carbon dioxide. 

Though their ability to take deep breaths or hold the breath differs from one mammal to another, all mammals use their lungs for breathing.

Some mammals store oxygen more efficiently than others, despite breathing in the same way as other mammals.

Seals, semi-aquatic marine mammals, store oxygen in their muscles and blood instead of in their lungs. This helps them to stay underwater for long periods. 

When they dive into the water, they breathe out instead of holding their breath like other mammals. 

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When underwater, seals rely on the stored oxygen in their muscles and blood, which helps them to sustain themselves underwater for a very long time. 

Not all mammals breathe in the same way. While some mammals breathe through their nose, some breathe through their mouth, and some can breathe through both or either.

How Does a Mammal’s Respiratory System Work?

All mammals need oxygen to survive, and this can be found in the air around them.  The respiratory system helps mammals to exchange crucial respiratory gases such as oxygen and carbon dioxide.  With the constant expulsion of carbon dioxide and oxygen intake, the mammals take the necessary gases from the air. 

While animals like fish and amphibians use their gills and moist skin to exchange gases, mammals use their lungs for breathing.

Mammals either breathe through the nose or the mouth.  The air is inhaled into the nose or mouth before passing into the pharynx.

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The pharynx is commonly known as the throat.  As part of the respiratory system, the air is inhaled through the mouth or nose and passed down through the animal’s throat.  The air is then passed to the trachea in the process.


The trachea, also known as the windpipe, is a tube that carries the air down from the pharynx to the lungs.  The trachea functions as a passage for air, warmed and moistening to protect the lungs from foreign particles.  This is achieved with the help of cilia.  The cilia are hairlike and run throughout the trachea, collecting the particles—the tube branches into two bronchi where the air will be passed into the lungs.


Mammals possess two lungs, and the bronchi split the air to reach either of the two lungs.  The bronchi are made of muscle and cartilage to help prevent the trachea from collapsing.  The bronchi are lined with mucus that also covers the rest of the respiratory system.  On most mammals, including humans, the right bronchus is larger than the left.  

The bronchus inside the lungs is divided further into five smaller bronchi.  These then provide air to the bronchioles.


Whilst bronchi are passages for the air to enter the lungs, bronchioles are tiny branches into which the bronchus divides. Whereas the bronchi are made up of cartilage and muscle, the bronchioles are muscles and tissues lined with epithelium. 

The bronchioles are smaller airways carrying the air to the alveoli.  


Once the air moves from the bronchioles, it is then passed to the alveoli.  Alveoli are at the end of the respiratory system, and this is where the gas exchange occurs.  Blood, rich with carbon dioxide, is pumped into the alveoli, where oxygen is absorbed and carbon dioxide is expelled. 

In the alveoli, the gases, oxygen, and carbon dioxide diffuse between blood and air.

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The respiratory system of almost all mammals works similarly to the way of a human’s respiratory system.  The air is moved with the help of the diaphragm moving.

The lungs of mammals are powered by the thin skeletal muscle that is called the diaphragm. The diaphragm pulls and pushes the lungs downwards and upwards.  To increase the volume of air into the lungs, the diaphragm pulls the lungs downwards.  To expel the air, the diaphragm pushes upwards, and the capacity of the lung becomes smaller.  

Depending on the pressure between the chest cavity and the atmosphere, the movement of gases inside and out of the lungs is determined. 

Depending on factors like the altitude and environment, mammals may breathe only through their mouth or their nose on occasion. 

How do Mammals Breathe in Extreme Temperatures?

Many mammals live in environments with extreme temperatures.  These can range from extremely cold to scorching temperatures.  

Some mammals hibernate in the winter, with the arctic ground squirrel being an example of one of the few arctic animals that hibernate.  They live in Alaska and Canada, and during hibernation, their body temperature lowers down to -3 degrees centigrade.  

The heart rate also drops to 1 bpm, and their blood reaches subzero temperatures.  The blood does not freeze as they cleanse their bodies of the particles that act as a nucleus for the formation of ice crystals.

Reindeer have adapted to the cold environments in which they live.  Reindeer breathe through their nose, which is adapted to warm the air they breathe in.  This allows them to breathe in without hurting their lungs.  

In warm temperature climates, such as America’s plains and deserts, mammals again have several adaptations.  

Mammals tend to be smaller in warmer climates and larger in colder climates.  As the animals are smaller, they lose their heat quickly and cool down faster.  In warm-blooded mammals, the heat loss is in proportion to their size.  As the mammals in these environments are generally smaller, the heat is lost quicker.

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How Do Mammals Breathe Underwater?

Mammals do not have the ability to breathe underwater.  Mammals that live underwater have to expose the top of their heads while resting or at the top of the ocean to get oxygen from the air.

Fish breathe underwater with the help of their gills, which helps pull the oxygen from water instead of from the air. However, unlike fish and other creatures that live and breathe underwater, ocean mammals cannot breathe in the same way. 

Dolphins, whales, and other sea mammals have a complex respiratory system like humans. As they use their lungs for breathing in oxygen from the air, they have to come to the ocean’s surface to intake air and exhale the carbon dioxide.

In the air around us, twenty percent of the air is oxygen; In water, the oxygen concentration is less than one percent. 

The oxygen concentration in water depends on the depth, the temperature of the water, and the amount of salt present in water. 

Fish have gills that are high oxygen catching membranes.  As mammals have lungs, the amount of oxygen in the water is not enough, and they need to reach the surface to enable them to breathe through their lungs effectively.

Mammals living underwater exhale first before breathing in also to ensure no water gets into their lungs. 

To boost the amount of oxygen in the lungs, the mammals living underwater hyperventilate intentionally. The term hyperventilate refers to rapid breathing, which helps in increasing the rate of losing carbon dioxide.

Marine mammals like dolphins and whales are voluntary breathers. This means that they need to remember that they have to breathe, unlike other land mammals who involuntarily and automatically breathe. 

It takes a fraction of a second for mammals living underwater to come to the water surface and fill their lungs with oxygen, which is especially true for dolphins.

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Why do Whales and Dolphins have Blowholes?

Ocean mammals such as whales and dolphins do not have noses like humans. Instead of a nose to breathe in and out of, whales and dolphins have a blowhole on the top of their heads.

Through the blowhole, they take the required oxygen from the air and exhale carbon dioxide. 

The muscles surrounding the blowhole ensure that the blowhole remains closed every time the whales and the dolphins go underwater.  The closure ensures that water can never get inside the lungs of these marine mammals. 

Whenever they reach the surface and require oxygen, the muscles surrounding the blowhole open the hole again.

Whales breathe warm air out of their blowhole, and a mist or spray can be seen. The spray that can be seen when a whale exhales does not come from their lungs but from the water collected on the top of their head.

When a whale exhales, the water is forced up, causing the water to be forced into the air.  This action ensures that no water gets in their lungs.

When dolphins inhale air through their blowholes, around 80% of the gas inside their lungs is exchanged with fresh air, which helps them hold their breath and stay underwater for up to 7 minutes.  

Compared to dolphins, humans can only exchange 17% of the air in their lungs with each breath. The speed at which dolphins can exhale air can be up to 100 mph. 

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Why do Some Whales Have Two Blowholes?

Some aquatic mammals have one blowhole on top of their heads, such as dolphins, killer whales, and beluga whales.

However, baleen whales (whales without teeth), including blue whales, humpback whales, and mink whales, have two blowholes on top of their heads.

Due to their vast size, these whales need to absorb much more surface oxygen than a smaller, faster whale. The extra air passageway allows the slower, larger whales to hold their breath for much longer.

Due to the way that baleen whales scoop up large amounts of food in one gulp rather than chasing their prey, they need to stay underwater longer.

The sperm whale is the exception.  The sperm whale can hold its breath for more than an hour with one blowhole.

Aquatic mammals have two passages to their lungs, as do humans. Like the lungs’ location in the human body, the lungs are located in the same area inside the whale’s body. 

Being mammals, humans, and aquatic mammals have diaphragms in their respiratory systems. The blowhole of the ocean mammals functions similarly to the mouth of a human.

What Mammal Can Hold Their Breath the Longest?

While humans and whales share similarities, it takes much longer for the marine mammals’ respiratory system to complete one cycle compared to the time that the respiratory system of humans takes. 

An average human in good health can hold their breath for approximately two minutes, although the Guinness World Record was set in 2011 at over twenty minutes.

When it comes to holding their breath for the longest amount of time in mammals, undoubtedly, the mammals living underwater top the list. 

As they use their lungs for breathing oxygen, they have to surface above the water and collect their share of oxygen. 

However, unlike any other mammals, marine mammals can hold their breath underwater for an extended period, despite not breathing underwater. 

Seals primarily live in the water and only come to the land to mate, give birth, or escape from natural predators such as sharks or killer whales. Seals not only can spend months at sea but can also sleep underwater with the capability of holding their breath for around 2 hours.

While an elephant seal can hold its breath underwater for around two long hours, dolphins can do this for around 10 minutes.  Fin whales can hold their breath for approximately 20 minutes, while sperm whales can hold their breath for 90 minutes.

In 2014, a Cuvier beaked whale held its breath underwater for around 2 hours and 17 minutes, breaking the previous record held by elephant seals.

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Common Respiratory Issues

Several things can go wrong with the respiratory system of mammals. Just like humans, other mammals may also suffer from various breathing issues. 

The respiratory system of any mammal is vulnerable to both diseases and toxins. Just as humans are affected by pneumonia and asthma, mammals like horses and cats are prone to develop respiratory issues.

Which Mammals Have the Smallest and Largest Lungs? 

The blue whale, which can weigh around 170 tonnes, has the largest lungs.  The tiny little bumblebee bat, weighing around only 2 grams, has the smallest lungs ever found in a mammal.

Sea otters are marine mammals with lungs that are three times bigger than any mammal of that same body mass.

Are there any mammals that have gills along with lungs? 

Some animals are capable of breathing both in water and on land but do not have functional lungs. These animals, however, are not mammals. 

Mammals have lungs as their breathing organs and not gills. Though animals like lungfish and salamanders have both lungs and gills, they aren’t mammals but fish.

From tree-climbing mammals like squirrels to flying mammals such as bats, from underwater mammals like dolphins and whales to burrowing mammals like rabbits and gophers, they all breathe with their lungs.

I hope that this has given an insight into how mammals breathe.

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