# Emerald tree monitor

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The **emerald tree monitor** (***Varanus prasinus***) or **green tree monitor**, is a small to medium-sized [arboreal](/source/Arboreal) [monitor lizard](/source/Monitor_lizard). It is known for its unusual coloration, which consists of shades from green to [turquoise](/source/Turquoise_(color)), topped with dark, [transverse](https://en.wiktionary.org/wiki/transverse) [dorsal](https://en.wiktionary.org/wiki/dorsal) banding. This coloration helps [camouflage](/source/Camouflage) it in its arboreal habitat.[2] Its color also makes the emerald tree monitor highly prized in both the pet trade and zoos alike.[3]

## Names

It is known as **wbl km** in the [Kalam language](/source/Kalam_language) of [Papua New Guinea](/source/Papua_New_Guinea).[4]

## Taxonomy

*Varanus prasinus* was first described as *Monitor viridis* by [John Edward Gray](/source/John_Edward_Gray) in 1831; however, Gray's original [holotype](/source/Holotype) (RMNH 4812 in the [National Natural History Museum](/source/Naturalis) in [Leiden](/source/Leiden)) was lost and the species was redescribed by Schlegel eight years later as *V. prasinus* using the found specimen.[5] The [generic](/source/Genus) name *Varanus* is derived from the [Arabic](/source/Arabic_(language)) word *waral* (ورل), which translates to English as "monitor".[6] Its [specific](/source/Species) name, *prasinus*, is [Latin](/source/Latin) for the color [green](/source/Green).

*Varanus prasinus* is a member of the subgenus *Hapturosaurus* and is closely related to several other [arboreal](/source/Arboreal_locomotion) species. However, this species may be [paraphyletic](/source/Paraphyly), as *[V. bogerti](/source/Bogert's_monitor)* was found to clade inside it. This indicates that *V. prasinus* may actually be composed of multiple species, although the paraphyly may instead be a result of [introgression](/source/Introgression) or [incomplete lineage sorting](/source/Incomplete_lineage_sorting).[7]

In addition to *V. prasinus*, this subgenus, whose members are all [allopatric](/source/Allopatric), includes *[V. beccarii](/source/Varanus_beccarii)* ([Aru Islands](/source/Aru_Islands)), *[V. boehmei](/source/Varanus_boehmei)* ([Waigeo Island](/source/Waigeo_Island)), *[V. bogerti](/source/Varanus_bogerti)* ([D'Entrecasteaux Archipelago](/source/D'Entrecasteaux_Archipelago)), *[V. keithhornei](/source/Varanus_keithhornei)* ([Cape York Peninsula](/source/Cape_York_Peninsula)), *[V. kordensis](/source/Varanus_kordensis)* ([Biak Island](/source/Biak_Island)), *[V. macraei](/source/Varanus_macraei)* ([Batanta Island](/source/Batanta)), *[V. reisingeri](/source/Varanus_reisingeri)* ([Misool Island](/source/Misool_Island)) and *[V. telenesetes](/source/Varanus_telenesetes)* ([Rossel Island](/source/Rossel_Island)).[8][9]

## Evolutionary history

The family [Varanidae](/source/Varanidae) probably originated in [Asia](/source/Asia) about 65 million years ago,[10] although some estimates are as early as the late [Mesozoic](/source/Mesozoic) (112 million years ago).[11] Monitor lizards probably migrated to Australia and the Indonesian archipelago between 39 and 26 million years ago.[12] All members of the *V. prasinus* species group (sometimes referred to as subgenus *Euprepiosaurus*) are found east of [Lydekker’s line](/source/Lydekker%E2%80%99s_line) in the Indo-Australian Archipelago.[13] This group probably originated in the [Moluccas](/source/Moluccas), although dating their origins is complicated by the paucity of the fossil record.[14] The absence of large placental predatory mammals east of [Wallace's line](/source/Wallace's_line) may be partially responsible for the radiation of the *V. prasinus* group in the Australo-Papuan region.[15]

## Distribution

Emerald tree monitors and their close relatives can be found on the island of [New Guinea](/source/New_Guinea) (split between [Indonesia](/source/Indonesia) and [Papua New Guinea](/source/Papua_New_Guinea)) as well as several adjacent islands,[16] and the northern [Torres Strait Islands](/source/Torres_Strait_Islands).[17] The green tree monitor is reported to thrive in lowland environments, including tropical evergreen forests, palm swamps and [cocoa](/source/Theobroma_cacao) plantations.[17]

## Description

The emerald tree monitor is about 75–100 cm (30–39 in) long with a slender body that helps it support itself on narrow branches. It uses its [prehensile](/source/Prehensile) tail and long claws to grip branches.[2][18][19] Unlike other varanids, this monitor defends its tail rather than lashing with it for defence when threatened.[20] The soles of the feet of the emerald tree monitor have enlarged scales which aid the lizard when climbing.[19]

## Ecology

When threatened, the emerald tree monitor will flee through vegetation or bite if cornered.

It is one of the few social monitors, living in small groups made up of a dominant male, several females, and a few other males and juveniles.[2]

## Diet

The emerald tree monitor's diet consists of large tree-dwelling [arthropods](/source/Arthropod), such as [katydids](/source/Tettigoniidae), [grasshoppers](/source/Grasshopper), other [orthopterans](/source/Orthopteran), [stick insects](/source/Stick_insect), [cockroaches](/source/Cockroach), [beetles](/source/Beetle), [centipedes](/source/Centipede), [spiders](/source/Spider) and [crabs](/source/Crab), as well as [birds](/source/Bird) and small [mammals](/source/Mammal) (such as [Moncton's mosaic-tailed rat](/source/Moncton's_mosaic-tailed_rat)).[21][22] Before swallowing stick insects, the lizards tear off the legs.[16] [Captive](/source/Captivity_(animal)) specimens tear off the limbs of rodents prior to eating them; as a result, they are capable of swallowing mammals of a considerable size: A 135-g lizard was documented as eating a 40-g rodent, almost one-third its size.[20][23]

On two occasions, this species has also been documented eating fruit in captivity by herpetologists — [Robert Mertens](/source/Robert_Mertens) observed them feeding on bananas, and Robert G. Sprackland fed bananas and cantaloupes to his captive specimens.[20][23] The latter did so after noticing that 12% of the feces in wild caught specimens consisted of plant material.[24]

Despite a lack of aquatic adaptations, the Bronx Zoo has recorded a captive emerald tree monitor swimming and foraging for food under shallow water.[25]

## Reproduction

Clutches consist of up to five [eggs](/source/Egg), each weighing 10.5–11.5 g (0.37–0.41 oz) and measuring about 2 by 4.5 cm (0.79 by 1.77 in). As many as three [clutches](/source/Clutch_(eggs)) are laid throughout the year; clutches have been laid by captives in January, March, April, November, and December. The female emerald tree monitor lays her eggs in arboreal [termite](/source/Termite) nests.[19] The eggs hatch between 160 and 190 days later, typically from June to November, after which the young eat the termites and the termite's eggs within minutes of hatching.[19] Sexual maturity is reached in about one year.[6]

## References

1. Wilson, Don W. & Burnie, David (2001). *Animal*. London: DK. p. 422. ISBN 978-0-7894-7764-4.

1. Bartlett, Patricia Pope & Bartlett, Richard D. (1996). *Monitors, Tegus, and Related Lizards: Everything About Selection, Care, Nutrition, Diseases, Breeding, and Behavior*. Woodbury, N.Y: Barron's Educational Series. p. 63. ISBN 978-0-8120-9696-5.

1. Bulmer, RNH (1975). ["Kalam Classification of Reptiles And Fishes"](https://web.archive.org/web/20201201112852/http://www.jps.auckland.ac.nz/document/Volume_84_1975/Volume_84%2C_No._3/Kalam_classification_of_reptiles_and_fishes%2C_by_R._N._H._Bulmer%2C_J._I._Menzies_and_F._Parker%2C_p_267-308/p1). *Journal of the Polynesian Society*. **84** (3): 267–308. Archived from [the original](http://www.jps.auckland.ac.nz/document//Volume_84_1975/Volume_84%2C_No._3/Kalam_classification_of_reptiles_and_fishes%2C_by_R._N._H._Bulmer%2C_J._I._Menzies_and_F._Parker%2C_p_267-308/p1) on 1 December 2020. Retrieved 22 September 2019.

1. Bennett, D. (1995). *A Little Book of Monitor Lizards*. [Aberdeen](/source/Aberdeen), UK: Viper Press.

1. King, Ruth Allen; Pianka, Eric R.; King, Dennis (2004). *Varanoid Lizards of the World*. Bloomington: Indiana University Press. pp. 225–229. ISBN 978-0-253-34366-6.

1. Weijola, Valter; Vahtera, Varpu; Lindqvist, Christer; Kraus, Fred (2019-03-14). ["A molecular phylogeny for the Pacific monitor lizards (Varanus subgenus Euprepiosaurus) reveals a recent and rapid radiation with high levels of cryptic diversity"](https://doi.org/10.1093/zoolinnean/zlz002). *Zoological Journal of the Linnean Society*. **186** (4): 1053–1066. [doi:10.1093/zoolinnean/zlz002](https://doi.org/10.1093/zoolinnean/zlz002). [ISSN 0024-4082](https://www.worldcat.org/issn/0024-4082)

1. Jacobs, H. J. (2003). *A further new emerald tree monitor lizard of the Varanus prasinus species group from Waigeo, West Irian (Squamata: Sauria: Varanidae).* Salamandra 39(2): 65-74

1. Ziegler, T.; A. Schmitz; A. Koch; & W. Böhme (2007). ["A review of the subgenus *Hapturosaurus* of *Varanus* (Squamata: Varanidae): morphological and molecular phylogeny, distribution and zoogeography, with an identification key for the members of the *V. indicus* and the *V. prasinus* species groups"](http://www.mapress.com/zootaxa/2007f/z01472p028f.pdf). *Zootaxa*. **1472**: 1–28. [doi:10.11646/zootaxa.1472.1.1](https://doi.org/10.11646/zootaxa.1472.1.1)

1. Zheng, Yuchi & Wiens, John J. (2016). "Combining phylogenomic and supermatrix approaches, and a time-calibrated phylogeny for squamate reptiles (lizards and snakes) based on 52 genes and 4162 species". *Molecular Phylogenetics and Evolution*. **94** (Pt B): 537–547. [Bibcode:2016MolPE..94..537Z](https://ui.adsabs.harvard.edu/abs/2016MolPE..94..537Z). [doi:10.1016/j.ympev.2015.10.009](https://doi.org/10.1016/j.ympev.2015.10.009). [PMID 26475614](https://pubmed.ncbi.nlm.nih.gov/26475614)

1. Schulte, JA; Melville, J; Larson, A (2003). "Molecular phylogenetic evidence for ancient divergence of lizard taxa on either side of Wallace's Line". *Proceedings of the Royal Society B: Biological Sciences*. **270** (1515): 597–603. [doi:10.1098/rspb.2002.2272](https://doi.org/10.1098/rspb.2002.2272). [PMC 1691285](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1691285). [PMID 12769459](https://pubmed.ncbi.nlm.nih.gov/12769459)

1. Vidal, N; Marin, J; Sassi, J; Battistuzzi, FU; Donnellan, S; Fitch, AJ; Fry, BG; Vonk, FJ; Rodriguez de la Vega, RC; Couloux, A; Hedges, SB (2012). "Molecular evidence for an Asian origin of monitor lizards followed by Tertiary dispersals to Africa and Australasia". *Biology Letters*. **8** (5): 853–855. [Bibcode:2012BiLet...8..853V](https://ui.adsabs.harvard.edu/abs/2012BiLet...8..853V). [doi:10.1098/rsbl.2012.0460](https://doi.org/10.1098/rsbl.2012.0460). [PMC 3441001](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3441001). [PMID 22809723](https://pubmed.ncbi.nlm.nih.gov/22809723)

1. Ziegler, Thomas; Schmitz, Andreas; Koch, André; Böhme, Wolfgang (2007). "A review of the subgenus Euprepiosaurus of *Varanus* (Squamata: Varanidae): morphological and molecular phylogeny, distribution and zoogeography, with an identification key for the members of the *V. indicus* and the *V. prasinus* species groups". *Zootaxa*. **1472**: 1–28. [doi:10.11646/zootaxa.1472.1.1](https://doi.org/10.11646/zootaxa.1472.1.1)

1. Molnar, Ralph E. (2004). ["The long and honorable history of monitors and their kin"](https://books.google.com/books?id=0e3OuHRRoIQC&q=Molnar,+R.E.+(2004)+The+long+and+honorable+History+of+Monitors+and+their+kin.+In++Pianka,+E.R.,+King,+D.R.+%26+King,%0AR.A.+(Ed),+Varanoid+lizards+of+the+World.+Indiana+University+Press,+Bloomington,+10%E2%80%9367&pg=PA10). *Varanoid Lizards of the World*. Bloomington, Indiana: Indiana University Press. pp. 10–67. ISBN 0253343666.

1. Sweet, Samuel S. & Pianka, Eric R. (2007). ["Monitors, mammals, and Wallace's Line"](http://www.zo.utexas.edu/courses/THOC/VaranidBiogeography.pdf). *Mertensiella*. **16**: 79–99.

1. Pianka, Eric R. (2006). [*Lizards: Windows to the Evolution of Diversity*](https://archive.org/details/lizardswindowsto00pian/page/247). Berkeley: University of California Press. p. [247](https://archive.org/details/lizardswindowsto00pian/page/247). ISBN 978-0-520-24847-2.

1. Cogger, H. G. (2000). *Reptiles & Amphibians of Australia*. 6th ed. Sydney: Reed New Holland. p. 371. ISBN 978-1-876334-33-8. [OCLC 807420701](https://www.worldcat.org/oclc/807420701)

1. Cogger, Harold & Zweifel, Richard (1992). [*Reptiles & Amphibians*](https://archive.org/details/reptilesamphibia00coggrich). [Sydney](/source/Sydney): Weldon Owen. ISBN 978-0-8317-2786-4.

1. Greene, Harry W. (1986). *Diet and Arboreality in the Emerald Monitor, Varanus Prasinus, With Comments on the Study of Adaptation*. Field Museum of Natural History. [OCLC 14915452](https://www.worldcat.org/oclc/14915452)

1. Robert George Sprackland (1992). *Giant lizards*. Neptune, NJ: T.F.H. Publications. pp. 137–142. ISBN 978-0-86622-634-9.

1. ["Varanus prasinus (Emerald Monitor)"](https://animaldiversity.org/accounts/Varanus_prasinus/). *[Animal Diversity Web](/source/Animal_Diversity_Web)*

1. ["Varanus Prasinus"](https://biocyclopedia.com/index/monitor_lizards/varanus_prasinus.php)

1. Balsai, Michael (1997). [*The General Care and Maintenance of Popular Monitors and Tegus*](https://archive.org/details/generalcaremaint00mich/page/6). BowTie. p. [6](https://archive.org/details/generalcaremaint00mich/page/6). ISBN 978-1-882770-39-7.

1. Koch, Andre & Arida, Evy (March 2017). "A coconut-eating monitor lizard? On an unusual case of frugivory in the melanistic Sulawesi water monitor (Varanus togianus)". *The Herpetological Bulletin*. **139** (129): 41–42.

1. Shuter, Avishai (2014). "A Novel Underwater Foraging Behavior Observed in Varanus prasinus at the Wildlife Conservation Society's Bronx Zoo". *Biawak*. **8** (2): 61–63.

## External links

- [Photos at Biolib.cz](https://www.biolib.cz/en/taxon/id59515/)
- [Ozanimals.com](http://www.ozanimals.com/Reptile/Emerald-Tree-Monitor/Varanus/prasinus.html)
- [Mampam.com](http://www.mampam.com/index.php?option=com_content&task=view&id=55&Itemid=41) [Archived](https://web.archive.org/web/20110723203208/http://www.mampam.com/index.php?option=com_content&task=view&id=55&Itemid=41) 23 July 2011 at the Wayback Machine

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Adapted from the Wikipedia article [Emerald tree monitor](https://en.wikipedia.org/wiki/Emerald_tree_monitor) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Emerald_tree_monitor?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.