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Why Does My Bearded Dragon Have His Mouth Open? 5 Reasons For This Behavior

Nicole Cosgrove

Bearded dragons have a lot of unique characteristics and traits, not least of which is their head bobbing and arm waving habits. A lot of their actions are a result of evolution and a throwback to the habits of their wild ancestors. One thing you may have seen your beardie doing and that has left you scratching your head is the opening of their mouth.

You may have seen your beardie basking on a rock with his mouth open, or hiding in cover and opening and closing his mouth. While it isn’t necessarily a negative sign, you should determine when he is doing it to find out whether he is in pain, suffering from anxiety, or simply self-regulating temperature.

Read on for nine reasons your beardie might have his mouth open.

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Reasons Your Beardie Has His Mouth Open

It is most likely that your beardie is regulating his temperature through an action known as gaping, but there are other causes why your pet reptile could be partaking in this odd-looking activity.

1. Gaping For Temperature Regulation

Lizards like bearded dragons are unable to sweat, which is the main method of regulating body temperature for humans. We sweat to cool the body down. A lizard must find other ways to regulate its body temperature, and opening its mouth is one such technique. In this instance, the action is called gaping and it vents excess heat from the body, therefore reducing the body temperature.

It is most common for a beardie to gape while he is basking, which usually means that he will do this while sitting on a rock under the heat lamp. If he is gaping in other areas of the tank, you may want to investigate to ensure that there are some cool spots where your dragon can go to cool down.

A bearded dragon’s terrarium should have cool and hot spots to allow it to heat up and cool down as required.

Bearded Dragon Heat Lamp
Featured Image Credit By: T. Miettinen, shutterstock

Do Bearded Dragons Sleep With Their Mouth Open?

It is not common for beardies to sleep with their mouth open. It could just be an unusual quirk of an individual beardie, but it may also be a sign that your dragon is too hot during the night. The nighttime temperature of the cage should be cooler than the daytime, and especially around the area where your bearded dragon sleeps.

Why Is My Bearded Dragon Sticking His Tongue Out?

As well as opening its mouth, your bearded dragon may stick his tongue out. This enables him to further reduce his body temperature to a reasonable level and is common during gaping.


2. Beard Stretching

A bearded dragon is so-called because of the beard around its neck. They can puff their beards out, and some can change the color or the intensity of the color in their beard. It is common for a beardie to stretch his beard, as it is known, when he feels threatened or when being aggressive. At this time, this beard will often turn black too. Although this is an instinctive reaction when being aggressive, the beardie may also perform the action at any time. They also stretch their beard as a means of exercising it and practicing the action.

Do Beardies Yawn?

Beard stretching can take many forms. Your beardie might stretch his neck, raise his head, open his mouth, and change the color of his beard. This can look like he is yawning. What’s more, bearded dragons, like most animals, do also yawn, and this is not a cause for concern.

Why Is My Bearded Dragon Opening And Closing His Mouth?

The continuous opening and closing of his mouth could be your bearded dragon stretching his beard and practicing.


3. Aggressive And Defensive Behavior

Most of us know the bearded dragon to be a calm, placid, and friendly little lizard. They usually get along very well with their human owner, and can even take well to strangers. However, they can still feel threatened and appear aggressive in nature if this happens.

bearded dragon close up
Image Credit: paintings, Shutterstock

Bearded dragons have a good understanding that humans are much bigger than they are, so rarely act aggressively towards us. But if you startle your beardie, he will act accordingly. His aggressive response might include opening his mouth and stretching his beard to try and intimidate and frighten you. Although an aggressive beardie is rare, the open mouth might be accompanied by hissing, charging, and even some biting.


4. Feeling Threatened

It isn’t just humans that can startle bearded dragons, of course. If you keep more than one in the same cage, which is not usually recommended, it could be that one beardie, usually the male, is being aggressive towards the other. This can startle the female, who may react by opening her mouth and hissing.

If you have other pets, they may be causing a startled reaction by approaching the cage, attempting to bat at the beardie, or by making loud noises and scaring the dragon. If your beardie’s cage is close to the window, it could even be the noise of passing cars or neighbor dogs that is causing an aggressive reaction.

Try to determine any noise or other activity that might be causing the reaction and look for ways to mitigate it. Move the cage to a quieter area, or away from the window, if this will help.


5. Respiratory Infection

The major cause for concern if your beardie has his mouth open all the time is a respiratory infection. These can occur when humidity levels are too high for too long. They are not adapted to breathe moist air, so you need to keep this moisture level down in the tank.

Keep any water bowl away from heaters, don’t use bark or other moisture-retaining items, and add more ventilation. Ensure that the moisture level does not rise above 40% for long. Signs of respiratory infection include gaping all day, even when not basking, along with mucus in and around the mouth.

If the infection is allowed to worsen, your dragon can become listless and lethargic, and you will need to seek veterinary assistance immediately because it cannot be treated successfully at home.

Bearded dragon showing tongue
Image Credit: Tambako The Jaguar, Flickr

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Should You Be Worried?

In most instances, it is quite natural for your bearded dragon to have his mouth open, but there are some cases where it can be cause for concern. It might be a sign that your beardie is startled or scared, that he is aggressive, or, worse still, that he has a respiratory infection that is affecting his breathing and needs immediate attention. It is more likely, however, that your beardie is gaping or regulating his body temperature and using his open mouth to vent hot air from his body.


Featured Image: Jon Glittenberg, Flickr

Nicole Cosgrove

Nicole is the proud mom of Baby, a Burmese cat and Rosa, a New Zealand Huntaway. A Canadian expat, Nicole now lives on a lush forest property with her Kiwi husband in New Zealand. She has a strong love for all animals of all shapes and sizes (and particularly loves a good interspecies friendship) and wants to share her animal knowledge and other experts' knowledge with pet lovers across the globe.