If you’ve ever wondered how many lungs snakes have, you’re not alone. As slithery, legless reptiles, snakes are fascinating yet mysterious creatures to many people.

If you’re short on time, here’s a quick answer to your question: snakes have only one lung. Keep reading to learn all about the unique respiratory system of snakes!

In this comprehensive article, we’ll cover everything you need to know about snake lungs and breathing. You’ll learn about the anatomy and evolutionary adaptations that allow snakes to thrive with just a single lung.

We’ll also compare the snake respiratory system to other animals and address some common questions people have.

The Unique Snake Respiratory System

Snakes have a truly remarkable respiratory system that is unique among terrestrial vertebrates. Let’s take a close look at how snakes breathe and why they only have one functioning lung.

Only the Right Lung Remains

Most snakes have two lungs, but only the right lung is fully functional. The left lung is either absent, vestigial, or greatly reduced in size. This is likely an evolutionary adaptation to allow room for an elongated trachea and the esophagus in the snake’s narrow body cavity.

Some sources hypothesize that having one larger lung, instead of two smaller lungs, allowed snakes to develop larger surface area for gas exchange. This may have been advantageous for meeting the high oxygen demands of an active predatory lifestyle.

How Snakes Breathe with One Lung

Despite having only one lung, snakes breathe just fine! Here’s how:

  • The right lung is elongated and extends nearly the full length of the snake’s body. This maximizes surface area for oxygen absorption.
  • The trachea connecting the lung to the head is also elongated. This allows thesnake to control each end of the lung independently.
  • Ribs extend along the length of the snake’s body, enabling ventilation of the elongate lung.
  • Special muscles between the ribs pull them apart to actively “pump” air in and out of the lung.

This setup allows for unidirectional airflow through the lung, optimizing oxygen uptake. Pretty clever!

Tracheal Lung

Some snake species take their respiratory adaptation one step further. They have a tracheal lung, where the terminal portion of the trachea expands into a lung-like structure. This adds even more gas exchange surface area off of the main lung.

Notable snakes with a tracheal lung include:

  • Rattlesnakes
  • Garter snakes
  • Rat snakes

The tracheal lung allows these active foragers to get even more oxygen, supporting their high metabolism. Evolution produces some amazing physiological innovations!

Evolutionary Adaptations for Breathing

Stretchy Lungs

Snakes have evolved some remarkable adaptations related to breathing. One of the most interesting is that they have very stretchy lungs. A snake’s right lung can extend most of the length of its body when breathing in fully.

This allows snakes to take in large gulps of air when needed, such as after long periods underwater or following strenuous activity. Their flexible lungs act as bellows, providing the flow of fresh air needed to meet their oxygen demands.

Unidirectional Airflow

Another neat evolutionary adaptation is that air flows in only one direction in a snake’s lungs. When breathing in, air enters the glottis (or windpipe) and then travels down the lung cavities before exiting the body. This unidirectional flow allows for efficient gas exchange.

The air moves in a constant direction rather than back and forth as it does in mammals’ lungs. This likely helps prevent lung collapse under pressure when snakes are squeezing through tight underground tunnels or constricting prey.

Slow Metabolism

Snakes also have a slower metabolism compared to similar-sized mammals. Their metabolic rates are around 1/10th to 1/20th of the expected rate based on body mass alone. This helps explain how snakes can hold their breath for so long while hunting or hiding underwater.

Anacondas, for example, have been documented staying submerged for up to 10 minutes at a time. Their slower use of oxygen allows them to get by on less frequent breaths. So snakes’ unique lung anatomy and physiology allow for flexibility and efficiency when it comes to meeting their respiratory needs.

Comparison to Other Animals’ Respiratory Systems

Mammals (Most Have Two Lungs)

Like snakes, most mammals have two lungs to breathe with. However, mammalian lungs are very different from snake lungs in a few key ways. First, mammalian lungs are enclosed in a rib cage, which provides protection and allows the lungs to expand and contract freely for breathing.

Snake lungs are elongated and run down the length of the snake’s body, without any bony protection. Second, mammalian lung tissue is very spongy and designed to maximize surface area, while snake lungs are smooth and simple inside. The extra surface area in mammal lungs allows for more gas exchange.

Finally, mammals typically breathe by inhaling fresh air and exhaling stale air. Snakes only have one direction of airflow, inhaling when they sniff and exhaling passively. Their lungs expand and contract like bellows along their body.

So while both snakes and mammals rely on lungs for respiration, the snake’s version is much simpler in structure and function. This likely contributes to the lower oxygen needs of snakes compared to active mammals like humans.

Birds (Have Rigid Lungs)

Birds have a unique respiratory system that also utilizes air sacs and lungs for gas exchange. Avian lungs are small and rigid, unlike the soft, spongy lungs of mammals. Air flows continuously in one direction through the bird’s lung and air sacs on both inhalation and exhalation.

This allows for efficient oxygen extraction, unlike mammal’s tidal breathing. Birds also have air sacs and hollow, pneumatic bones which aid their lightweight, optimized respiratory system. Snake lungs lack these specializations that make the bird respiratory system so complex and efficient.

Both snakes and birds developed the use of air sacs for respiration, but birds took the concept further to achieve exceptional oxygen delivery. A bird’s high metabolic demands for flight required such an adaptation. Snakes, as ectothermic reptiles, can get by on a much simpler lung structure.

So while birds and snakes share some respiratory similarities like air sacs, the bird version is much more advanced.

Amphibians and Fish (Have Gills)

Snakes differ greatly from amphibians and fish when it comes to respiration. Amphibians such as frogs and salamanders utilize both gills and lungs at some stage of their life. Gills allow gas exchange when they are aquatic as larvae and juveniles.

As they morph into adults, amphibians begin using lungs to breathe air. Lungs allow them to absorb oxygen from the air rather than water. Fish solely rely on gills for respiration and cannot leave water like amphibians can. Meanwhile, snakes have only lungs throughout their life cycle to breathe air.

They do not possess gills for extracting dissolved oxygen from water like fish and larval amphibians do. The snake respiratory system is designed for terrestrial life, not aquatic living. While amphibians and fish take in oxygen from water, snakes must get all their oxygen from air.

Lungs allow snakes to be highly mobile on land to hunt for food rather than being restricted to water. So snakes are very different from amphibians and fish when it comes to breathing organs.


As you now know, snakes are perfectly adapted to thrive with only one functioning lung. While this unique respiratory system may seem unusual compared to most mammals, it works remarkably well for these incredible reptiles.

The stretchy, unidirectional lung allows for efficient oxygen exchange while the snake’s slow metabolism reduces energy and air needs. So next time you see a snake slithering by, remember the unique internal anatomy that allows its breathing and movement!

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