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Why Your Chameleon Keeps Its Mouth Open

In chameleons and other reptiles, holding the mouth open is called “gaping” and it’s usually normal but sometimes it can indicate a number of problems. So, what does it really mean when your chameleon keeps its mouth open?

Temporary gaping can occur when the chameleon is drinking, regulating temperature, or shedding skin, and is no issue. However, gaping can also indicate stress and fear. Prolonged gaping is a symptom of heat stress, MBD, URI, Stomatitis, or injury. These problems need immediate medical attention.  

Let’s explore the possible causes of your chameleon gaping…

Discover Why Your Chameleon Is Gaping

Have a look at this infographic we made for you first. It will help you to find out why your chameleon is keeping its mouth open and what you can do to help.

After that, we will explain all the reasons in detail.

why is my chameleon's mouth open decision tree

Gaping Due To Drinking Behavior

Chameleons do not drink from water bowls, but instead, catch water droplets from the air and sip water drops from leaves. Like many reptiles, they have the ability to absorb some water through their skin, but certainly not enough to sustain them.

In their natural habitat, the rainforest, chameleons have evolved a special behavior that triggers them to drink. When they feel the rain falling, they will open their mouths a little and will begin licking up water drops that have landed on leaves.

The rain is an instinctive stimulus, and chameleons will not start their drinking behaviors without this signal. 

In captivity, it is essential to mimic the rain by misting at least twice a day. This keeps the humidity levels in the enclosure high and will trigger the chameleon to drink.

It is very important to mist for 3-5 minutes, as the behavioral trigger only kicks in after 2 minutes of rain! For this reason, it is necessary to devote time to misting and not just give the enclosure a quick spritz. 

If you see your chameleon with its mouth open during or after misting the enclosure, it is likely to be part of the usual drinking behavior.

For drinking, the chameleon should not be stretching the mouth open extremely wide. You should also see the tongue coming forward to collect water.

Observe your chameleon to make sure that this behavior is temporary, and it returns to keeping its mouth closed after it has finished drinking.

Get familiar with your chameleon’s regular, baseline behavior so that you can notice abnormalities when they occur. If a little mouth opening happens in a predictable pattern following each misting session, it is perfectly normal. 

chameleon can't close mouth
A chameleon that is drinking will repeatedly open its mouth.

Gaping Due To Shedding Skin

Chameleons shed their skin approximately every 4-8 weeks. They do this to allow for growth, to keep the skin clean, and to help shed parasites. When the skin is coming off, it does so in small pieces. The process feels irritating, tight, and itchy. 

During a shed, your chameleon is more likely to be reactive and may mouth gape as part of the defensive display discussed above. However, you may also notice them stretching their mouths wide in a different way.

Opening the mouth wide can help them stretch their body out of the old skin, and loosen any sticky bits from around their face. 

Stretching to release a molt is no problem. Observe your chameleon if you notice increased gaping during a skin shed. If the behavior disappears once the skin is shed, you can be pretty sure there was nothing to worry about. 

If your chameleon’s skin is not shedding cleanly, and you see them gaping and twisting a lot, you can help them out a little bit. Increase your misting to help soften the molting skin.

You can even gently wipe at the stuck pieces using a moist Q-tip or clean cloth. Don’t peel away big pieces of the skin though, as you may cause damage. 

At 2:10 you can clearly see this chameleon opening its mouth wide and stretching to get rid of the old skin.

Gaping Defensively Due To Fear Or Stress

Chameleons open their mouths wide when they feel fearful of potential predators or competition from other chameleons. They gape as a sign that they are prepared to bite, and will sometimes make slow lunges as if to bite before actually doing so. 

If your chameleon is gaping for this reason, the open mouth will also be presented alongside other signals: 

  1. The chameleon will become very bright or extremely dark vivid colors. 
  2. It will open its mouth wide and gape continuously.
  3. It will inflate its throat and puff up to look as big as possible. 
  4. It will turn side-on to the threat to display the colors well.
  5. It will follow the threat with its eyes and open mouth.
  6. It will coil its tail up very tightly.
  7. It will hiss.
  8. It will draw up its front legs and possibly open its claws up.

Take a look at these signs being displayed very clearly by this nervous chameleon. 

This cause of gaping is quite normal and nothing to worry about, as long as it is an acute response to something frightening. To make it stop happening, you should remove the scary stimulus.

Perhaps you had your hand in the enclosure, perhaps lots of people are in the room, or maybe the cat is sitting peering into the habitat. Whatever it is, remove this perceived threat. 

Once the threat is removed, continue to watch your chameleon from a place out of sight. The chameleon should return to normal colors and stop mouth gaping once the threat is gone. If so, this is a great sign that the gaping is part of regular defensive behavior. 

However, this is not something you want to see all the time. Frequent defensive mouth gaping shows that your chameleon is anxious and chronically stressed.

Chronic stress is dangerous, as the prolonged sense of threat causes cortisol levels to remain high in the body for far too long.

Cortisol suppresses bodily functions such as growth and digestion, and will eventually result in illness and damage if not relieved. 

If your chameleon is frequently gaping and showing other defensive responses, evaluate the possible causes. Aim to keep your chameleon relaxed, happy, and healthy. Check out this article to find out exactly how to do this!

Gaping Due To Normal Temperature Regulation

Chameleons are reptiles, which means they are cold-blooded and cannot regulate their own body heat internally. Instead, they have a range of behaviors that allow them to use the environment to heat and cool themselves.

In order to warm their bodies and get energy, they must bask in the sun. In captivity, the sun is replaced by another heat source such as a lamp. 

In preparation for basking, chameleons instinctively climb upward. This is because they evolved in the forest, and know that the sunlight and heat can be found nearer the canopy.

Despite living in captivity, this will not change. A chameleon will climb up and rest on an exposed branch to get warmer, and will climb down to lower levels and shelter to get cooler. 

A chameleon that is too cold and wants to get warmer will:

  1. Move upward, closer to the heat source.
  2. Become darker in color, so as to absorb more light.
  3. Have its mouth closed.

A chameleon that is too hot and wants to get cooler will: 

  1. Move downward, toward the cool, moist substrate and shelter from the light.
  2. Change to pale or bright colors to reflect the light away and prevent absorption.
  3. Open its mouth to let heat escape from the increased surface area and damp oral mucosal tissues. 

Once you observe gaping in relation to these other signs, the chameleon is approaching heat stress and may not be able to cool itself down without your help. Do not let gaping continue too long before intervening. 

Gaping Due To Abnormal Temperature Regulation/Heat Stress

Heat stress happens when the chameleon is too hot, and is failing to cool itself down by sheltering and changing to bright, pale colors. Once it starts gaping, it is approaching dangerous territory.

The next step is that the chameleon will close its eyes, and this is a huge red flag. You need to act quickly to change the environment to help it cool down.

This chameleon has adopted bright, light colors that reflect heat and light away. It is gaping and was seeking shelter. It is overheating.

If your chameleon is outside, especially being handled, you need to bring it in from the sunlight and let it get away from your body heat. If it is near a sunny window but in its enclosure, close the blind and move the enclosure away.

Mist the enclosure, especially the substrate, to make it moist. Evaporation will cool the habitat and the chameleon, much like sweating does for our skin. Try placing an ice pack on the outside of the enclosure.

Move the heat lamp out for the moment and assess the heating system in the enclosure. The habitat should have areas of ambient temperature, and areas for basking at higher temperatures.

The chameleon should have the freedom to move between them to regulate body temperature.

The basking area should be high up, and accessible by an exposed branch. Use a thermometer to measure the temperature along the branch.

Bear in mind that you need to measure not at the branch level, where the feet of your chameleon will be, but a few inches up, where the surface of its back will be. 

Chameleons are not very cautious when it comes to heat sources. They should not be able to climb too close to the heat lamp or UVB light. Chameleons often suffer burns this way. 

Suggested ambient and basking temperatures for common chameleon species

Chameleon SpeciesMale Ambient TemperatureMale Basking TemperatureFemale Ambient TemperatureFemale Basking Temperature
Veiled Chameleons (Chamaeleo calyptratus)75-82°F24-28°C85-90°F30-32°C73-78°F23-26°C80-85°F27-30°C
Panther Chameleons(Furcifer pardalis)75-82°F24-28°C87-90°F30-32°C73-78°F23-26°C82-85°F28-30°C
Jackson’s Chameleons(Trioceros jacksonii)75-82°F24-28°C85-88°F29-31°C73-78°F23-26°C78-83°F26-29°C

Naturally, common sense and individual experience should be applied to the suggested temperature ranges.

For example, if you observe that your chameleon is always trying to cool down or always trying to warm up, you may need to change your environmental temperatures. 

Overheating is bad news for chameleons, especially females. Being too warm can lead to increased clutch sizes, increase likelihood of egg binding, and as a result, higher mortality.

Watch out for gaping, as well as the other signs of overheating we discussed today. 

Gaping Due To Mouth Rot (Stomatitis)

Mouth rot or stomatitis is unfortunately another common and quite serious illness among chameleons and other reptile pets. It is a group of symptoms that result from bacterial infection.

It can take hold when your chameleon suffers tiny injuries to the mouth area, or has food lodged between the teeth which decays. 

While infection and injury are the primary causes, mouth rot is made much more likely as a result of poor husbandry. Contributing factors include:

  • Lack of hydration
  • Nutritional deficiency, especially lack of vitamin A
  • Chronic stress
  • Lack of UVB light
  • Lack of hygiene

Mouth gaping is not a primary symptom of mouth rot. However, thanks to the inflammation, pain, and mucus deposits around the mouth, a chameleon with stomatitis is likely to gape and can’t close its mouth effectively. The symptoms of mouth rot are:

  • Redness around the mouth
  • Swelling around the mouth
  • Resultant open or crooked mouth position
  • Yellow discharge and mucus, which may build up around the mouth
  • Dark deposits on the teeth
  • Thick, stringy saliva
  • Disinterested in eating and drinking
  • Swelling of the whole head area

Mouth rot can be treated if caught early. However, you will likely need to give your chameleon a course of antibiotics and so need to visit the vet.

The mouth area will need to be gently cleaned every day with a suitable disinfectant such as betadine, but this should be done as instructed by your vet. Many wound cleaning treatments that are suitable for humans are not suitable for chameleons. 

This chameleon is in the early stage of a mouth rot, which you can see at 1:37. Good thing the owner caught that so early. In such an early stage, the chameleon will probably not keep its mouth open all the time. However, the worse it gets the more the chameleon will keep its mouth open.

Gaping Due To Injury

Injuries are not common but can and do happen. An injury from a fall could damage the jaw of your chameleon and cause them to hold their mouths open.

Also, an injury caused by another chameleon might damage the mouth, especially if they are biting at one another. Even feeder insects have the potential to injure your pet’s face and jaw, causing gaping. 

If you notice an injury to your chameleon’s face or mouth, it would be best to consult a vet. They may prescribe antibiotics, clean the wound effectively, and give you guidance on how to aid in healing at home. 

Injuries can be avoided with mindful care. For example, ensure that your chameleon has appropriate browse and branches to climb on safely. Ensure that the environment does not have sharp edges or hazards that could cause cuts. 

Try not to feed any live insects that are too large. If hand-feeding worms or grubs, you can deliver them head first to reduce the chance of them biting your chameleon.

Lastly, chameleons are solitary creatures and should not be housed together. Fights and injuries are quite likely to happen in this situation. House them separately, and so that they cannot see each other. This will also reduce the chance of chronic stress. 

Gaping Due To Metabolic Bone Disease (MBD)

Metabolic Bone Disease (MBD) is a prevalent problem among chameleons and is very dangerous. MBD occurs when there is a shortage of calcium in the body.

This happens because there is a deficiency of calcium supplementation and vitamin D in the diet, or a lack of UVB light available. UVB light (or sunlight) allows the body to create vitamin D and absorb calcium more effectively. 

As a result of calcium deficiency, the chameleon’s body starts to draw calcium supplies from the bones in order to keep organs functioning.

Over time, this results in something called “bendy bones”. The chameleon’s body will begin to become deformed, and it will not be able to move and walk confidently. 

When this happens, the jaw bones become warped and deformed too. Once they are bent out of shape, the mouth will not be able to close all the way around.

You may notice that the mouth is always open, or that gaps have appeared in places. The tongue will no longer fit inside, and may not function correctly for shooting and hunting. 

MBD is a very serious condition and needs urgent veterinary attention. Unfortunately, while the vet can prevent further damage, they cannot undo the deformities that have already occurred.

This means that a warped jaw will never return to sealing perfectly again. You may have to offer your chameleon special care such as hand feeding and cleaning around the mouth area for the rest of its life. 

Whilst it is dangerous and difficult to resolve, MBD is thankfully quite easy to prevent. To prevent MBD, it is essential to provide proper calcium supplementation, sometimes reinforced with Vitamin D to help with absorption.

It is also important to have a UVB lamp, and if possible, to allow your chameleon to experience direct sunlight occasionally. 

This video shows you what metabolic bone disease can do to a chameleon. The video shows even x-rays of a chameleon suffering from MBD and how you can prevent it.

Gaping Due To Upper Respiratory Infection (URI)

A less common illness that can cause mouth gaping in chameleons is an upper respiratory tract infection, or URI. A URI affects the respiratory system and so makes it difficult for the chameleon to breathe. 

The first symptom of a URI is that the chameleon will point its nose skyward. This position opens the airways fully, allowing maximum airflow through the nose to the lungs. 

In the video below, you can see how the chameleon is showing this symptom and progresses to stage 2.

The 2nd stage symptom is mouth gaping. The chameleon starts gaping in order to breathe through its mouth. This shows that it can no longer breathe through its nose and is getting sicker.

When this happens, you may start to hear wheezing, or even small popping sounds. You should not be able to hear a healthy chameleon breathing.

At this stage, the illness is developing into a serious medical emergency. You should go to the vet immediately. 

The symptoms of the final stage of URIs are: nose pointing skyward, mouth gaping, wheezing, and closed, sunken eyes. Once your chameleon reaches this point, it is in critical condition and could die within the day. Get to the vet immediately for antibiotics and remedial care. 

Fortunately, URIs do not happen often among pet chameleons. URIs can be avoided through proper husbandry and hygiene.

Maintaining correct humidity levels and temperatures are important factors in preventing URIs. Also, sourcing chameleons from reputable breeders is essential to prevent disease being spread through the pet chameleon population. 

Pierre And The ReptileCraze Team
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