An adult green tree monitor climbing on a branch

Green Tree Monitor 101 (aka Emerald): The Full Guide

Green tree monitors are fascinating reptiles that can make great pets (for the right owner). These gorgeous lizards are quite unique and fun to spectate!

But this is not a pet that you should purchase on a whim. In fact, we actually discourage most owners from getting one (despite their beauty).

Emerald tree monitors require a lot of experience and commitment to keep, which means they’re not beginner-friendly. But if you’ve been doing this for a while and want to learn about green tree monitor care, this guide has you covered!

Species Summary

The green tree monitor (Viranus prasinus) can be found in tropical forest areas of Papua New Guinea, Indonesia and even parts of Australia. This intelligent reptile is popular because of the classic monitor appearance it has, in addition to the bright emerald color of its body.

It’s an excellent choice for reptile caretakers with intermediate to advanced experience in reptile husbandry. Even though it is not really known for aggressive behavior, it is still a lizard that needs to be handled with caution.

The green tree monitor also has many day-to-day maintenance tasks that are better suited to owners with more experience. 

Appearance & Colors

The green tree monitor has a classic “monitor” look with a long body, long limbs and a prehensile tail. Sharp claws give it the ability to easily climb trees and branches.

An adult green tree monitor climbing on a branch

This gorgeous monitor, much coveted by monitor enthusiasts, can be found in colors ranging from bright green/emerald to turquoise. It has transverse dorsal bands and sometimes has light-blue dots.

The combination of the darker bands and spacing between the colored scales give this lizard a very textured appearance. It’s mesmerizing to look at!

Green Tree Monitor Size

The typical green tree monitor size is about three feet long when fully grown. Despite this length, these reptiles stay rather slim as they age.

Expert Tip: The size of the emerald tree monitor means that you will have to build a pretty large, custom enclosure (we cover this a bit further down in the guide). This is something important to consider because that cute little monitor you got as a baby will very quickly become a three foot adult!


The average lifespan of a green tree monitor is 10 to 15 years when given proper care and housed in the right environment. If you’re looking for a pet reptile that has the potential to become a long-lasting companion and source of interest, then the green tree monitor is a pretty good choice!

For anyone willing to invest the time, money and energy it takes to care for one of these creatures, the green tree monitor will definitely pay them back with years of excitement, learning and improved caretaking skills.

On the flip side, the long life expectancy of this monitor, combined with the rigorous care it needs, can be overwhelming for some people. Be honest with yourself when deciding if this is something you want to try!

Green Tree Monitor Care

Green tree monitor care is for owners with some experience. If you are new to the world of reptile husbandry, then this species is not going to be for you.

We really recommend that only people with an advanced knowledge of reptile care even attempt ownership of these monitors.

Here’s why:

The green tree monitor needs a lot of things like a large living space, a specialized diet, controlled temperature and humidity and handling expertise. Plus, monitors are extremely messy, and the enclosure and water area will need to be constantly cleaned.

Enclosure Size

Building the enclosure is where things can start to get a little tricky. You’re not going to be able to get away with some flimsy, small set-up. This is going to have to be a custom-made enclosure that is large enough and sturdy enough to be a long-term home for your green tree monitor.

The absolute minimum size of your enclosure should be 4 by 2 by 4 feet. However, it’s always better to go even bigger if you have the space for it.

Expert Tip: The rule of thumb is that the enclosure needs to be twice the length of the monitor.

You can make the enclosure out of plastic, wood, glass or a combination of these items. Glass sides aren’t always the best because emerald tree monitors, like many other reptiles, are often confused by the glass. They can really get hurt by bashing themselves against the glass.

Habitat Setup

When it comes to putting together the ideal green tree monitor habitat, there are a few things that you are going to have to take into consideration.

Emerald tree monitor in a large enclosure

Green tree monitors are arboreal, so you’ll have to provide lots of places to climb. They are also going to need places to hide, things to play with or explore, and you will need to have a good substrate.

When choosing a substrate, make sure that it is one that will help to retain moisture without becoming soaked. This will help to maintain a good level of humidity within the enclosure. Cypress mulch, certain mosses or a combination of soil and sand work pretty well. Make sure that the substrate layer is deep enough for burrowing.

Other habitat enhancements include lots of branches for climbing, reptile hides, artificial plants and nesting boxes. Don’t be afraid to experiment if you have the space for it!

Temperature & Lighting

Green tree monitors require a pretty specific temperature and lighting setup in order to thrive. This doesn’t need to be anything complicated, but you’ll need to make sure that certain requirements are always met.

The enclosure that you create for your green tree monitor will need to have a temperature gradient.

In order for a monitor to regulate its body temperature, it needs to go back and forth between a warmer area and a cooler area. You can create this in your enclosure by assigning one side of the enclosure as the basking (warmer) side and leaving the other side as the cool-down section.

The basking area should always remain at a toasty 95 to 100 degrees Fahrenheit. This temperature can be achieved using a basking lamp. Put the basking lamp above the basking spot, and that should do it. Don’t put this lamp too close to where your monitor is going to hang out because it could get a serious burn.

The rest of the enclosure should remain between 78 and 82 degrees Fahrenheit with a nighttime temperature around 78 degrees.

Expert Tip: The other crucial step is going to be adding a source of UVB lighting to the enclosure. This kind of light helps reptiles produce vitamin D3 through calcium absorption. We recommend purchasing a bulb that is a kind of a heat and UVB combo.


An enclosure humidity level of 80 percent is essential for the overall comfort and health of these lizards. Fortunately, maintaining this level of humidity isn’t difficult, and you can usually get away with hand misting the enclosure a couple of times a day.

If hand misting isn’t something you want to bother with, you can also install an automatic mister. Either way works fine. Having a bowl of fresh water in the enclosure will help maintain the humidity as well.

It’s best not to guess at the humidity level. A reliable and accurate hygrometer will let you know that the levels are correct, so you can rest easy knowing that your pet is fine.


Green tree monitors need a constant source of fresh, clean water. Unfortunately, these monitors aren’t always the neatest pets, and you are going to have to change out the water a couple of times a day.

This is a very important task that you can’t afford to get lazy with. Unclean water can quickly lead to bacteria and disease.

Expert Tip: Make sure to thoroughly clean the water bowl once a week as well.

Food & Diet

Green tree monitors are not overly picky eaters, and they will eat a wide variety of foods like crickets, mealworms, dubia roaches and even pinky mice. Monitors that have been trained to eat from tongs can try canned locusts or grasshoppers too.

It’s perfectly fine to feed your emerald tree monitor every other day. Make sure to only give it what it can eat in one feeding, and use a supplemental calcium and vitamin to dust the prey prior to feeding time.

Potential Health Issues

Before you commit to caring for a green tree monitor, it’s important to make sure that there is a veterinarian in your area who is experienced in the care of these exotic reptiles. There are several health issues that are common with green tree monitors, and having a knowledgeable vet is going to be super important.

Viranus prasinus resting

Interestingly enough, dehydration can be a real problem for green tree monitors. This is one of the reasons why it’s so critical to always have a source of clean water in the enclosure.

Parasites are another health issue that can plague an emerald tree monitor. It is going to be very important to get fecal testing done on a regular basis. Have your lizard tested before you bring it home and then regularly after that.

If you notice that your monitor is not eating well, is kind of sluggish or has excess mucus, then it could have a respiratory infection. This is pretty common for monitors, and it requires medical attention.

Behavior & Temperament

Green tree monitors are not aggressive by nature, but they will bite if they feel threatened. Their natural tendency is to flee from a dangerous situation, but you still will need to use caution if your pet is new and untrained.

Being diurnal, these lizards are very active during the day, and you’ll see them climbing, basking and exploring their enclosure. Because they are arboreal, these monitors love to climb, so they will need plenty of climbing enhancements.

Expert Tip: This is one of the great things about emerald tree monitors. They’re always up to something, making them a joy to spectate.

As with many reptiles, male green tree monitors should not be housed together. They are extremely territorial, and they have the tendency to fight. A bonded male and female can be put together, but these monitors really do better in their own separate enclosures.

Handling Advice

If you’re looking for a pet reptile that you’ll be able to pick up and handle, then the green tree monitor is probably not the right choice for you. As mentioned above, this lizard is not aggressive, but it prefers to be left alone.

However, you can train it to tolerate being near you during feeding time or when it’s time to clean the enclosure. Time and patience are really all it takes!

Once the monitor sees that you are not going to hurt it, and it starts to trust you, then it may even let you hold it. However, we still suggest keeping handling to a minimum (even if you can get your lizard to this point).


Green tree monitor care is something that should only be attempted by owners with a fair bit of experience. Anything else is unfair to these lizards (and won’t be fun for the owner either).

But if you fit the bill and are ready to give these reptiles a chance, go for it! These pets are incredibly rewarding to own.

If you decide to give it a shot we’d love to hear your stories! We might even add them to this guide.