Why Chameleons Keep Their Mouth Open


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When you first get a chameleon you notice all sorts of little quirks about their behavior. One of these you will notice pretty early on is that chameleons will sometimes sit with their mouth wide open like a yawn.

So why do chameleons keep their mouth open? The main reasons Chameleons keep their mouth open is because they are either too hot, drinking water or they are displaying a defensive posture. They do not keep their mouth open to yawn because chameleons don’t yawn as a result of being tired like you or I do.

This article will tell you all the reasons why chameleons keep their mouth open and what you can do to prevent this and make them more comfortable.

Chameleon is keeping its mouth open because it is too hot

Chameleons, like all reptiles, are cold blooded. This means they need a heat source to warm themselves up. In the wild, of course, they can just hang out on a branch and sunbathe until they’re warm enough, they won’t get a tan though!

When they’re warm enough they move down a few branches and find a bit of shade where things are cooler and where they can just chill out and wait for an unfortunate passing insect to snack on.

In captivity, we need to provide our chameleons with a heat source. This should be a spotlight complete with a bulb that has sufficient wattage so that your chameleon can bask under it, as they would do the sun in the wild. In captivity, this provides a temperature gradient for your chameleon to move between in order to regulate its body temperature.

This is easy enough to achieve but there are a few factors that make things too hot for your chameleon and make them feel uncomfortable. None of us want that so we need to cool things down.

Fixing temperature issues for your chameleon

First, you need to check the temperature accurately to see if any adjustments are required. To do this I used a simple thermometer gun like this one from Amazon. This enabled me to measure the temperature and the ambient temperature of the enclosure in different places

The temperatures for each species should be as follows:

  • Veiled Chameleon Temperatures – Basking: 85°F – 90°F Ambient: 75°F – 82°F
  • Panther Chameleon Temperatures – Basking: 87°F – 90°F Ambient: 75°F – 82°F
  • Jackson Chameleon Temperatures – Basking: 85°F – 88°F Ambient: 75°F – 82°F

If once you’ve done this and you find the temperatures to be too hot you can fix this problem by checking a number of things about your chameleon’s enclosure:

  • Bulb temperature – This is the first thing to check. You know reptiles are cold blooded and that the sun is blazing hot so your first instinct, naturally, is to get the hottest bulb you can find with a high wattage. Don’t do this.

    I used a 50watt halogen reflector bulb and this always gave a basking temperature of around 90°F and the rest of the enclosure at around 75°F. You may need a lower or higher one depending on the climate where you live but 50 watt is a good starting point.
  • Bulb distance – Once you have the correct bulb but your chameleon is still keeping its mouth open you need to check the distance of the perch from the basking bulb itself. Your chameleon needs to be able to get directly underneath the beam but if the perch you provide for this is too close it will be too hot.

For my veiled chameleon, the perch was around 15 centimeters away from the bulb. This meant my chameleon’s back was around 10 centimeters away. My chameleon never showed signs he was too hot as a result of this setup.

To move the perch distance simply wait for your chameleon to move and then just open the enclosure door and gently lower it until it’s in the correct position.

  • An unnecessary separate heat source – This is something that bugs me about some pet shops. They sell unnecessary items to first time chameleon owners.

    This is either because they want to make more sales or they simply don’t know enough about keeping chameleons. So many times I’ve seen chameleon keepers with a separate heater alongside their basking bulb.

If you have a separate heat source don’t feel bad about it as you’re just doing what you were told is best for your chameleon. I’m here to tell you though that you don’t need one at all and that the heat from the basking bulb is more than enough to meet your pet’s needs. So if you have a separate heater go ahead and remove it and see if that makes things cooler.

  • Glass or screen? – This is an ongoing debate amongst chameleon keepers and there’s no definitive answer as to which one is best as there are pros and cons to both. Personally I would, and did, opt for a screen enclosure for my chameleon.

    I think it’s more difficult to maintain a steady temperature in a glass enclosure and things can easily get too hot in there.

    A screen enclosure also provides a better airflow which helps to prevent stagnant air and reduces the risk of your chameleon getting a respiratory infection.

Get my recommendations for what cage you need and what to put in it here.

An extra sign of your chameleon being too hot is if it’s showing a light coloration all the time. Although this looks pretty, chameleons, veiled chameleons in particular, tend to show a neutral medium green color to indicate things are generally all OK.

Read more about chameleon temperature here.

Chameleon is keeping its mouth open as a defensive posture

A chameleon just sitting with its mouth open all the time is usually a temperature related issue but chameleons also gape their mouths open when they feel threatened and stressed. You’ll know the difference once you get to know the situations it does this in.

At first, my chameleon would do this pretty much every time I went near his enclosure. He did eventually somewhat tolerate my presence but chameleons are very territorial and inside his enclosure is his.

Amusingly my chameleon seemed to think the whole of my living room was his. He tolerated me being there but whenever someone new entered he’d often sit there, turn black and keep his mouth wide open whilst keeping his eyes firmly transfixed on the new person in the room.

Of course, this made my girlfriend feel most welcome when she first met him!

So if your chameleon is either turning very bright and colorful, turning black, making itself larger and opening its mouth it means its simply a defensive posture rather than a temperature issue.

Again, don’t feel bad about this as there’s no real way to avoid this altogether but there are ways to minimize these defensive situations which you can read about in my related article.

The video below highlights both the defensive posture and being too hot at the same time. The uploader thinks his chameleon is yawning but it is actually enacting a defensive posture, probably as a result of having a camera in its face, chameleons aren’t keen on being filmed too closely!

You can tell it’s being defensive by that fact it puffs its body and chin out as well as opening its mouth.

The uploader says his chameleon does this every morning. If so I would wager it is also too hot as it is way too close to its basking lamp. I would move this chameleon’s perch lower to make him more comfortable.

Chameleon is opening its mouth to drink

As you probably know, chameleons don’t drink standing water and instead drink water droplets from leaves. In captivity, this means we need to mist our chameleons using either an automatic mister or hand spray bottle. Water can also be provided by a dripper system at the top of a cage.

I hand misted my chameleon with a spray bottle and I always did so until he began to open and close his mouth. This meant the drinking response had begun, meaning my chameleon was aware water was nearby and that he was thirsty enough to drink.

I know this seems obvious but you’d be amazed at how difficult it can sometimes be to make chameleons aware that there’s water nearby and they ought to drink it! Many chameleons won’t even drink while anyone’s watching.

So if you’re concerned about your chameleon having its mouth open in this situation then don’t be as this is a good sign that your chameleon is healthy and just wants to drink the refreshing water you’re providing.

You can read more about a chameleon’s water needs in a separate article I wrote here.

Chameleon is taking big gulps of air

This is the worst but also least likely scenario. If your chameleon is keeping its mouth open all day whilst sitting under its basking lamp all day, seems unalert, isn’t eating or drinking, is taking big gulps of air whilst tipping its head up and has a lot of mucus in its mouth then your chameleon most likely has a respiratory infection.

Chameleon is opening mouth because it is shedding

The last scenario that needs mentioning is when your chameleon sheds its skin. This should be very obvious when this is happening as your chameleon’s skin will be flaking off. Don’t worry there’s nothing wrong and this is perfectly normal behavior.

When I watched my chameleon shed I’d often see his mouth open really wide in order to get rid of the skin around his mouth and head. He’d also get a bit annoyed as it probably is a bit annoying and uncomfortable to get skin off like that.

Opening its mouth whilst shedding is, therefore, nothing to be concerned about.

You can read more about chameleon skin shedding in my article here.


Chameleons will mainly sit with their mouths open if they’re too hot or being defensive. They don’t open their mouths due to yawning. I hope you have a better understanding as to why your chameleon is keeping its mouth open and how to make them more comfortable as a result of reading this article.

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6 responses to “Why Chameleons Keep Their Mouth Open”

  1. Callahan avatar

    I see you’ve linked to my video in this post. My chameleon yawns every morning when she wakes up, whether she is near the lamp or not. The yawn doesn’t seem to be temperature dependent. To me, it appears to be more like a morning stretch.
    Additionally, if it was a temperature issue, I would expect to see her open her mouth during the afternoons of the summer months when her cage gets the hottest, and not just once within the first few minutes of the light turning on.

    1. Dave avatar

      Hey thanks for the comment. Yawning as a result of tiredness or stretching isn’t known chameleon behaviour. What are perceived as yawns are mainly a result of them getting defensive and/or trying to intimidate you. For the record I don’t think yours is gaping its mouth as a result of being too hot I was just highlighting it as a possibility. Cleopatra is definitely doing it to intimidate you in the video though as she puffs up and does a little shake after the second time, both are signs of being defensive. If she does it every morning maybe there’s something near her cage that bothers her? If she seems happy and healthy though, and she certainly looks that way, I wouldn’t worry too much.
      She is beautiful by the way but are you sure she is a she? The size of her casque and her size in general suggests Cleopatra is male to me. Has your chameleon laid eggs before?

  2. Rod avatar

    My veiled male does a yawn followed by a shake every morning
    Is the shake normal or something to worry about

    1. Dave avatar

      Hi Rod,

      Thanks for the comment. The shake is nothing to worry about it’s just a part of their threat display. My veiled did it a lot.

      1. Francesco Vellutino avatar
        Francesco Vellutino

        What do you mean by shake exactly? I just purchased a panther chameleon and noticed that sometimes he opens his mouth and does a weird movement (like a little shake) that kind of looks it ike he is “choking”. I thought he might have eaten and was struggling with swallowing his food at first but I’m not too sure. Again, he doesn’t do it very often, i’ve only seen him doing it a couple of times.

        1. Dave avatar

          Yes it can look like they’re choking but it’s not they’re just doing a defensive display it’s nothing to worry about. It’s difficult to explain more what I mean but the way you explained it sounds like the shake I’m referring to.

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