By now you may have seen your bearded dragon do all kinds of things such as head bobbing or waving, but why would a bearded dragon hold its mouth open?
The sight of a dragon just sitting slack-jawed, mouth gaping for all the world to see is a strange one and can leave dragon owners worried.
So what do you need to know about open-mouth bearded dragons to make sure you are taking the best possible care of your pet?
Let’s find out!
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Reasons why bearded dragons hold their mouths open range from simple temperature regulation to severe illness. Let’s dive into each possibility (and their sub-possibilities)!
Here’s a quick video recap.
1. Regulating Temperature
At first, the answer seems quite simple. Beardies open their mouths because they are getting warm and want to let excess heat dissipate.
However, diving a little deeper into the matter, one finds a bit more to this behavior than just that.
Maintaining the ideal body temperature is the main reason that beardies may sit with their mouths open.
Dragons do not sweat, and much like dogs, their mouths are the easiest way for them to expel extra body heat. 
This behavior is not always explicitly to cool down, though. Dragons may open and shut their mouths periodically to maintain an optimal temperature.
If your beardie has its mouth open while basking in the heat, it is most likely heat regulation. This is called “gaping.”
Bearded Dragon Gaping
One of the behaviors they often display is opening their mouth for long periods, also known as “gaping.” Keep in mind that gaping does not necessarily mean that your beardie is getting too hot.
They are likely just maintaining the internal temperature that they are most comfortable with. However, if your beardy shows signs of discomfort, avoids its heating lamp, or gapes even in hiding, it could be cause for concern.
If you think that your dragon is getting too hot, make sure that parts of its tank act as a ‘thermal’ refuge. The experienced bearded dragon owner will know that you need to maintain a thermal gradient in your bearded dragon’s tank. The correct temperatures are crucial.
The overall temperature should come to around 95° Fahrenheit. That said, different areas should be at different temperatures to accommodate a beardies needs.
EXPERT TIPS: The basking area should be kept at between 95° and 100°F. Your dragon will also need a cool spot with temperatures between 75° and 80°F.
Because bearded dragons are ectotherms, they need lower temperatures to sleep comfortably. Therefore, the ideal temperatures for resting areas are between 70° and 75°F.
If the temperature is even throughout your dragon’s tank, they do not have the reprieve they may need to cool down. Furthermore, they will struggle to sleep.
Beardies need a couple of things to help maintain their body temperature. First, the heat lamp, the main heat source, should be a 40 or up to 75W infrared bulb.
Placing the bulb too close to the designated bearded dragon basking area will cause a beardie to get too hot as well. 
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Bearded dragons shed their skin. Young beardies can shed every couple of months. As they mature, beardies shed less frequently.
At full maturity, starting at around 18 months or so, bearded dragons may shed only a couple of times a year.
A good beardie stretch helps loosen the skin around the neck area. The behavior is usually accompanied by ‘puffing,’ further loosening skin and preparing the dragon for its next shedding.
Although it is mostly associated with shedding, a dragon may stretch their beard by opening their mouth long before they are due to shed.
This behavior may keep the skin around the beard area supple and avoid it from growing too tight.
3. Aggressive Behavior
Bearded dragon behavior is usually placid. They are not inclined to aggression, given they have enough space to move around in and they don’t have too many other beardies to contend with.
However, they are territorial and can get agitated by several things that we humans might not notice.
A bearded dragon standing tall is more likely to display a submissive hand gesture. However, should one decide to stand its ground, an open dragon mouth is one of the ways they might signal their aggression.
If you think that your dragon’s open mouth is a sign that they are angry, there are a few other tells you can look for.
If your dragon is bobbing their head, it is a clear indicator that they are asserting dominance. They are ready to get scrappy if the situation requires it. An open mouth, in addition to the head-bobbing, puts emphasis on the intent.
A puffed-up or blackened beard, hissing, and a tall stance also indicate aggression.
EXPERT TIPS: To help your beardie manage their aggression, provide them with enough hiding places where they can go to calm down.
Several things could trigger your dragon’s aggression. It helps to understand these so that you can identify the reason that your dragon has its mouth open and help if needed:
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Fellow Bearded Dragons
Beardies are solitary animals. In nature, they form loose groups, but they don’t share the kind of cooperative behavior we associate with social animals. While they can tolerate each other, they do require a period of time to themselves.
When they feel a territory or resource is challenged, they will put on displays of dominance. For example, a submissive dragon will ‘wave’ their arm to show that it will not take the challenger up on the threat.
Suppose the challenged beardy is confident that they measure up to the challenger. They may then open their mouth and display clear signs of aggression. The submissive beardy may do better in their own separate tank.
EXPERT TIPS: If your dragons display this behavior, you may need to separate them. This may extend as far as placing the dragon tanks in separate rooms. However, aggression can continue if they still see each other.
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Let’s break down defensive behavior a bit more by looking at the potential causes behind it.
Bearded dragons will usually exhibit a fear response to larger animals. This entails their classic waving gesture, displaying their submission.
Unfortunately, this gesture does not communicate a sign of stress to the excited dog or curious cat.
Undeterred by the submission, other animals might continue to upset a dragon, either through their actions or by the noise they make.
That leaves a beardy little choice. In a situation where they feel particularly threatened and don’t feel safe retreating to the safety of a hiding spot, they must defend themselves.
It starts with more beardie body language.
An open mouth, combined with hissing and any other combination of displays of bearded dragon aggression, soon follow.
At this point, your dragon is in full ‘fight for survival’ mode. It may seem a funny sight to behold, but a beardie in this state is suffering extreme stress.
Related: Why Do Bearded Dragons Wave Their Arms?
Children at play can distress our beards greatly. All members of the Pogona family have highly acute hearing. In nature, this helps them steer clear of predators and detect an attack in time to escape.
In captivity, this trait causes bearded dragons stress. Their sharp hearing alerts beardies to the faintest of sounds.
It’s safe to say that children are not particularly quiet. As a result, beardies can interpret the sound of chaotic play as a serious threat to their well-being.
As is the case with other pets, a dragon will usually choose to retreat to the safety of a hiding spot. Even so, beardies will still experience extreme distress.
Should they feel that the threat is inescapable, they may choose to stand their ground in a desperate attempt to ward off the perceived threat.
In this case, a dragon might hiss, the beard could turn black, and the mouth may be stretched open.
Beardies are not ideal for homes with small children. If you have children, you should place your dragon tank in a room that the kids don’t use for play.
Sound can remain a problem, even in a separate room. It is therefore important to try and isolate your beardie from noise as best you can.
If the behavior persists, and you suspect that it is linked to children at play, you might even need to soundproof the room in which your dragon lives. The final option at your disposal would be to responsibly rehome your dragon.
It is difficult not to have a small chuckle when you see a beardy have a hissy fit, mouth gaping at the sight of a new lamp.
Unfortunately, new items around the home can distress a bearded dragon immensely. They are very focused on their surroundings.
New objects don’t usually appear out of nowhere in their natural habitats. So it makes sense that the sudden arrival of new objects can seem strange and potentially dangerous to bearded dragons.
There is no easy way to introduce a beardie to a new item. Sometimes they are not bothered at all by something new. Other times they become utterly obsessed.
While it may not be a solution, you should introduce any new items at as much distance as possible. Then, with time your dragon may become accustomed to the item and accept it as part of its environment.
If your dragon finds something particularly distressing, you might have to move the said item to a different space altogether. If it is a new permanent fixture, you will have to move your dragon.
Keep in mind that moving your beardie is a very stressful experience for them as well.
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Many bearded dragon owners prefer to place their bearded dragon near an open window. The idea is that your beardy can enjoy the view.
Unfortunately, there are a couple of problems with this. First, regarding your dragons sitting with an open mouth, the suburban outside world offers plenty of things that beardies could see as a threat.
Other pets and children, as well as vehicles, may seem dangerous to your bearded dragon. Birds invoke the strongest reaction. In their natural environment, birds are dragons’ natural predators.
Maintaining your dragon tank is also more difficult when you need to compensate for direct sunlight. However, the pros don’t justify the cons, especially if you notice your beardy open their mouth more frequently.
4. Mating Behavior
An open mouth is no sign of romantic intent in dragons. However, you will notice them doing this a lot more often at these times. This is because their hormones cause several behavioral changes, including heightened aggression. 
Curiously, a solitary male may still display this sort of behavior with no female or competing males nearby.
Bearded dragons usually mate in the summer months. So if your beardy opens their mouth a lot more frequently during this time, it may be that they are experiencing the biological responses associated with the time of year.
5. Respiratory Disease
Infection of the respiratory tract is relatively rare in bearded dragons. The condition is brought on by poor tank ventilation and higher levels of humidity over a prolonged period. Most Pogona are used to more dry air.
Extended periods of humidity can cause a respiratory infection that may be life-threatening in severe cases.
EXPERT TIPS: Keep humidity levels under 35-40%. If you live in a humid area, you may need to use a dehumidifier.
Additional measures, such as mesh insulation and removing any water-retentive materials such as tree bark. A smaller water bowl kept in the cool area of the tank can help as well.
If you suspect that your beardie might have a respiratory infection, you should immediately take them to a reptile vet.
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Do bearded dragons open their mouth when happy?
When bearded dragons open their mouths to regulate their temperature or keep to an ideal temperature, they are likely content. It is, however, not a direct indication that they are happy. On the contrary, in many cases, it could communicate aggression or distress. It can also be a sign of a respiratory infection.
How do you know if your bearded dragon is happy?
A happy bearded dragon shows few signs of aggression, basks often, and is comfortable being held for short periods. If it is not puffing itself up, hissing, or waving in fear, then it is probably quite comfortable. Remember, a healthy bearded dragon is also a happy one, so a good diet, a healthy weight, and a properly maintained vivarium that isn’t too crowded all help make a bearded dragon happy.
Is it bad when a bearded dragon opens its mouth?
It is not usually a sign that anything is wrong when a bearded dragon opens its mouth. Most of the time, a bearded dragon opens its mouth because it is regulating its body temperature. However, it can also be a display of aggression or distress. In rare cases, it may indicate a respiratory infection.
Bearded dragons keep their mouths open for several reasons. First, they do this while basking to regulate their body temperature.
It is also a common sign of aggression, especially when displayed alongside other aggressive behaviors. However, at times it is a defensive behavior.
In rare cases, an open mouth can indicate a respiratory infection.
In general, an open mouth is not a cause for alarm. Instead, try to understand why your bearded dragon’s mouth is ajar and address the issue if needed.
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Have you seen your bearded dragon opening his mouth? Let us know in the comments below!