Emerald Tree Monitor Fact File
Varanus prasinus
Weight
300g
(10.6oz)
Length
75-100cm
(3.3ft)
Length
Wild - 14 years
Captive - 25 years
conservation status
IUCN
Lest Concern
A Jewel in the Forest!
The emerald tree monitor is a striking green lizard which is well adapted for life in the trees of New Guinea and a number of islands to the North of Australia. Their long slender tail is prehensile allowing them to grab on to branches giving them support as they move through the trees.
Unlike most lizards this species is social and they will form small groups which move through the forest and rest together.
Appearance
What does an Emerald Tree Monitor look like?
This striking monitor species has a slender body which is covered with bright emerald green scales. These are streaked with black crossbars running across the body. On the underside their scales are white, yellow or a lighter shade of green. Under the throat some individuals have a yellow patch of scales. The bottoms of their feet are black. Each foot has long claws to help them hold trees when climbing.
Their long thin tail is round in shape and is prehensile allowing them to hold on to things with their tail. This tail is the same length as their body.
An adult emerald tree monitor will measure between 75 and 100cm (30-39in). They weigh 300g (10.57oz). Males are typically slightly larger than females.
Adaptations
How does the Emerald Tree Monitor survive in its habitat?
Emerald tree monitors have a prehensile tail. This means it is able to grab on to items allowing them to support their body while climbing through the trees. Their feet are also specially adapted to help with grasping branches.
The colouration of the emerald tree monitor is an adaptation that allows them to blend in with the trees in which they spend most of their time.
On top of their head is a spot known as the parietal eye, this opening is sensitive to light like the eye but does not develop a full image. It is thought to be used by reptiles which have the adaptation to allow them to regulate their activity throughout the day.
Diet
What does an Emerald Tree Monitor eat?
The emerald tree monitor is a carnivore. Most of their diet is made up of insects, primarily katydids, though some small mammals, frogs, geckoes, eggs and crabs may also be eaten.
Captive animals have been seen eating small amounts of fruits and vegetables but they cannot digest cellulose and it is unlikely these are eaten in the wild.
Range
Where do you the find the Emerald Tree Monitor?
Emerald tree monitors are primarily found on the island of New Guinea within both the Indonesian and Papua New Guinea portions of the island. They can also be found on a range of smaller islands in the Torres Strait between Australia and New Guinea.
Various unconfirmed reports have been made from within Australia in the past but it is believed that these were a number of different species.
Habitat
Where can an Emerald Tree Monitor survive?
They can be found in rainforests, lagoons and swamps. As human habitations have expanded in to their range they have adapted to live in cocoa plantations.
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Reproduction
How does an Emerald Tree Monitor produce its young?
Breeding takes place throughout the year and a female may lay up to three clutches throughout the course of the year.
Little is known of their mating behaviour. Following a successful mating the female will deposit her clutch of two to four eggs in to a termite mound. The termites then seal the mound and this provides a suitable temperature for the incubation of the eggs. Eggs may also be deposited in to a tree hollow.
This is similar to a behaviour exhibited by the lace monitor in Australia. The lace monitor female returns to free the hatchlings once they hatch though it is has not been observed if this occurs in the emerald tree monitor.
Eggs are typically laid between June and November.
Incubation takes 160 to 190 days. Following hatching the young have food available straight away from the termites which are in the nest with them. After eating these they exit the termite mound.
Young emerald tree monitors grow quickly. After hatching they may grow 4 times as large within the first 3 months of their life. Males grow quicker than females meaning they reach a larger size at the same time as the males.
They are sexually mature at 2 years old.
Behaviour
What does the Emerald Tree Monitor do during its day?
The emerald tree monitor is one of the few lizards which is social. Males and females will form small groups headed by a dominant male with many females.
They are primarily arboreal. Emerald tree monitors are well adapted for a life in the trees. Their prehensile tail acts like a fifth leg allowing them to easily hold on and move through the trees.
Predators and Threats
What stops the Emerald Tree Monitor from surviving and thriving?
In most areas of their range they represent the apex predator and do not face any threats. Snakes and birds may hunt for eggs and hatchlings of this species.
Humans affect their population in very small numbers through export for the pet trade. They can be bred in captivity and this should reduce the numbers caught from the wild.
Quick facts
They are a popular animal for display in zoos and to be kept as pets.
The emerald tree monitor is also known as the green tree monitor.
References
Swanson, S. and Parish, S., 2011. Field Guide To Australian Reptiles. 2nd ed. New South Wales: Pascal Press.
Burnie, D., 2011. Animal. 3rd ed. London: DK
Genomics.senescence.info. 2020. New Guinea Green Tree Monitor (Varanus Prasinus) Longevity, Ageing, And Life History. [online] Available at: <https://genomics.senescence.info/species/entry.php?species=Varanus_prasinus>
[Accessed 28 June 2020].
Shea, G., Allison, A., Parker, F. & Tallowin, O. 2018. Varanus prasinus. The IUCN Red List of Threatened Species 2018: e.T42485751A101752115. https://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T42485751A101752115.en. Downloaded on 28 June 2020.
Krynock, J. 2019. "Varanus prasinus" (On-line), Animal Diversity Web. Accessed June 28, 2020 at https://animaldiversity.org/accounts/Varanus_prasinus/
Hoglezoo.org. 2020. Green Tree Monitor | Utah's Hogle Zoo. [online] Available at: <https://www.hoglezoo.org/meet_our_animals/animal_finder/green_tree_monitor/> [Accessed 28 June 2020].
Smithsonian's National Zoo. 2020. Emerald Tree Monitor. [online] Available at:
<https://nationalzoo.si.edu/animals/emerald-tree-monitor> [Accessed 28 June 2020].
Green Tree Monitor: AMNH (no date) American Museum of Natural History. Available at: https://www.amnh.org/exhibitions/lizards-and-snakes-alive/nose-hounds/a-world-of-smells/green-tree-monitor (Accessed: February 26, 2023).
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