Green Tree Monitor Care Sheet

Green Tree Monitor Care Sheet

The green tree monitor (Varanus prasinus) is also known as the emerald monitor. These are about 3’ long, arboreal lizards native to New Guinea and adjacent islands. They prefer lowland, tropical environments with high humidity in palm stands and rainforests.

Green tree monitors have a long head and neck, a slender body, long claws for climbing, and a long, prehensile tail. Coloring is bright green to jade green with a darker transverse dorsal banding.

Due to their housing and feeding requirements, green tree monitors are at least intermediate-level pet reptiles. When kept appropriately, they can be expected to live up to 15+ years.

Minimum recommended enclosure size for green tree monitors

The minimum recommended enclosure size for a single green tree monitor is 4’L x 2’W x 5’H. This may seem huge, but keep in mind that these are quite large, active lizards that need opportunities for a lot of climbing throughout their enclosure. Of course, if you can manage it, larger is always better! A 4’L x 2’W x 4’H enclosure would be good for a smaller one as it is growing, or with use of the expansion kits.

We do not recommend housing multiple green tree monitors in the same enclosure.

Do green tree monitors need UVB?

Green tree monitors do require UVB lighting for best health. UVB lighting helps provide a clear day/night cycle, provides all of the vitamin D that your pet needs, strengthens the immune system, facilitates better digestion, and other benefits.

Here are the best UVB bulbs for green tree monitors:

For 6”-10” away from the highest branch

For 10”-20” away from the highest branch

For best results, use a bulb that is at least half the length of the enclosure, and house it in a fixture with a reflector. Position the lamp on the same side of the terrarium as the heat lamps.

They are also likely to benefit from plant grow lights as part of their environment as well. Add a ~6500K LED or T5 HO fluorescent grow lamp to provide extra illumination, as well as help any live plants in the enclosure to thrive.

Most people do a 12 hours on and 12 hour off lighting schedule. However, you can also do longer times on during the summer and shorter times on in the winter to mimic the actual sun.

Best temperature for green tree monitors

Green tree monitors do best with a basking area temperature of 100-120°F measured with a temperature gun, with the rest of the enclosure being an ambient 75-82°F, as measured by at least two digital probe thermometers. Temperatures can get as low as 70-73°F at night.

We recommend providing heat for your green tree monitor with a cluster of halogen heat bulbs placed above the basking branch. You will want enough lamps to evenly heat an area at least the size of the lizard’s body. If temperatures are too high you can use a lamp dimmer or rheostat to lower the intensity. We do not recommend ceramic heat emitters (CHEs), red bulbs, or blue bulbs, as these are not as effective.

Best humidity levels for green tree monitors

Green tree monitors are a tropical species, so the humidity inside their enclosure should be fairly high: around 75% on average and up to 100%. Humidity can be measured via digital probe hygrometer, with the probe placed in the middle of the terrarium.

Humidity can be increased by misting your monitor’s enclosure with a large pressure sprayer or automatic misting system. This is often how they also drink water, when misting the leaves in the enclosure. Be sure to mist the enclosure well enough to provide droplets and small pools on leaves, but do not oversaturate. You can allow the enclosure to dry out a little between misting. If you need more help maintaining humidity, you can install a cool mist humidifier. We suggest providing a large water bowl as well, though you may never see them use it. We recommend refilling with clean water daily and sanitize with a reptile-safe disinfectant weekly.

Recommended substrates for green tree monitors

Although green tree monitors spend most of their time in the trees, they do occasionally spend time at ground level. Providing a layer of naturalistic substrate (“bedding”) in the enclosure will help maintain correct humidity as well, cushion your lizard against falls, provide a digging medium, and also help make your enclosure more attractive! 

We recommend the following substrates for green tree monitors:

Layering clean, chemical-free leaf litter on top of the substrate can help with humidity as well as add enrichment value.

We suggest substrate to be at least 4” deep and completely replaced every 3-4 months. Remove poop and urates daily, along with any contaminated substrate.

How to decorate a green tree monitor enclosure

An empty enclosure makes for a bored lizard, reducing its quality of life. Keep your pet entertained and engaged with its environment with the strategic use of décor items that encourage it to exercise natural behaviors!

Since green tree monitors are arboreal, at bare minimum you will need large, sturdy branches for them to bask and climb on. However, it’s best to include other items, such as:

You want to make sure all branches are securely anchored into the walls/floor of the enclosure to prevent collapse and accidental falls.

What to feed to a green tree monitor

Green tree monitors are primarily insectivorous, which means that they require a mostly insect-based diet to get the nutrition that they need. They can also be given whole-prey and other items occasionally, but insects should be about 90% of their diet. How often they need to eat depends on life stage: Hatchlings and juveniles should be fed daily, but once they near adulthood, reduce feedings to every other day if they have good body condition. This species is very active and has a fast metabolism.

Here are some foods that are appropriate for a green tree monitor to eat:

Recommended supplements for your green tree monitor

You will also want calcium and vitamin supplements to help keep your green tree monitor healthy. We recommend a calcium without D3 lightly dusted on all foods except whole prey. Any of these choices would be good:

We also recommend a multivitamin to include 1-2 days per week. Any of these options are good to consider:

How to handle your green tree monitor

Reptiles generally don’t appreciate petting and handling in the same way that dogs and cats do. Regarding green tree monitors specifically, they are known for getting stressed easily with over handling.

If you want to build a trusting relationship with your pet green tree monitor, you will want to develop a foundation of positive interactions. Offering food from feeding tweezers or your hand works well as an initial bribe, and it’s best to get the lizard to come to you rather than simply grabbing it.

Here are some more tips for success:

  • Don’t grab the lizard from above. Instead, scoop from below.
  • Support as much of its body as possible.
  • Start with short handling sessions at first, then gradually make them longer.
  • Put the lizard back in its enclosure only when it’s calm.


*This care sheet contains only very basic information. Although it’s a good introduction, please further your research with high-quality sources. The more you know, the better you will be able to care for your pet!

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