Monitor lizard

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Template:Short description Template:Automatic taxobox Monitor lizards are lizards in the genus Varanus, the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and one species is also found in south America as an invasive species.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> About 80 species are recognized.

Monitor lizards have long necks, powerful tails and claws, and well-developed limbs. The adult length of extant species ranges from Template:Convert in some species such as Varanus sparnus, to over Template:Convert in the case of the Komodo dragon, though the extinct megalania (Varanus priscus) may have reached lengths of more than Template:Convert. Most monitor species are terrestrial, but many are also arboreal or semiaquatic. While most monitor lizards are carnivorous, eating smaller reptiles, fish, birds, insects, small mammals, and eggs, a few species also eat fruit and vegetation.<ref name="EoR">Template:Cite book</ref>

EtymologyEdit

The generic name Varanus is derived from the Arabic word {{#invoke:Lang|lang}} waral [Standard Arabic] / {{#invoke:Lang|lang}} warar [colloquially] / {{#invoke:Lang|lang}} waran [colloquially], from a common Semitic root ouran, waran, warar or waral, meaning "lizard beast".<ref name="Sprackland">Template:Cite book</ref>

In English, they are known as "monitors" or "monitor lizards". The earlier term "monitory lizard" became rare by about 1920.<ref>Google ngrams</ref> The name may have been suggested by the occasional habit of varanids to stand on their two hind legs and to appear to "monitor",<ref name="Sprackland" /> or perhaps from their supposed habit of "warning people of the approach of venomous animals".<ref>Horatio Nelson, Matthew Henry Barker, The Life of Nelson Revised and Illustrated. With Original Anecdotes, Notes, Etc. By the Old Sailor, 1836 p. 35</ref> But all of these explanations for the name "monitor" postdate Linnaeus giving the scientific name Lacerta monitor to the Nile monitor in 1758, which may have been based on a mistaken idea by Linnaeus that the German word Waran (borrowed from Arabic) was connected to warnen (to warn), leading him to incorrectly Latinize it as monitor ('warner', 'adviser').<ref name="Zimmern">Template:Cite book</ref>

Austronesian languages spoken across Southeast Asia, where varanids are common, have a large number of slightly related local names for them. They are usually known as biawak (Malay, including Indonesian standard variety), bayawak (Filipino), binjawak or minjawak or nyambik (Javanese), or variations thereof.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Other names include hokai (Solomon Islands); bwo, puo, or soa (Maluku); halo (Cebu); galuf or kaluf (Micronesia and the Caroline Islands); batua or butaan (Luzon); alu (Bali); hora or ghora (Komodo group of islands); phut (Burmese); and guibang (Manobo).<ref name="bayl">Template:Cite journal</ref><ref name="gaulk">Template:Cite journal</ref>

In South Asia, they are known as Template:Transliteration in Meitei, mwpou in Boro, Template:Transliteration घोरपड in Marathi, Template:Transliteration உடும்பு in Tamil and udumbu ഉടുമ്പ് in Malayalam, Template:Transliteration in Bhojpuri, gohi (गोहि) in Maithili, in Sinhala as තලගොයා / කබරගොයා (Template:Transliteration), in Telugu as uḍumu (ఉడుము), in Kannada as Template:Transliteration (ಉಡ), in Punjabi and Magahi as गोह (goh), in Assamese as gui xaap, in Odia as ଗୋଧି (godhi), and in Bengali as গোসাপ (Template:Transliteration) or গুইসাপ (Template:Transliteration), and गोह (goh) in Hindi and गोधा (godhā) in Sanskrit.<ref>Template:Cite book</ref>

The West African Nile monitor is known by several names in Yoruba, including Template:Transliteration, Template:Transliteration, and Template:Transliteration. In Serer<ref name="Kasteel" /><ref name="Kastee2">Kesteloot, Lilyan, Dieux d'eau du Sahel: Voyage à travers les mythes de Seth à Tyamaba. Editions L'Harmattan, 2007, p. 11, Template:ISBN [1] (accessed 27 March 2025)</ref> and amongst the Wolofized-Serers<ref name="Kastee2" /> of Kaolack, it is known as mbossé (or mboose in Serer<ref name="Kasteel" />)<ref name="Kasteel" /><ref name="Kastee2" /> or bar in Wolof (pronounced barrr with a long "R").<ref name="Kasteel" /> Mbossé is the tutelary and traditional totem of the city of Kaolack, (formerly part of the Serer precolionial Kingdom of Saloum, now part of modern-day Senegal).<ref name="Kasteel">Template:Cite book</ref> The mbossé is also one of the totems of the noble Joof family born of Guelwar matrilineage,<ref name="C.Diop Ant">Diop, Cheikh Anta, The Cultural Unity of Black Africa: The Domains of Patriarchy and of Matriarchy in Classical Antiquity. Third World Press, 1978, p. 190, Template:ISBN</ref> which is one of the many Serer maternal clans. The mbossé or mbosseh (in Gambian English) is one of the Serer religious festivals,<ref>Template:In lang Niang, Mor Sadio, [in] Ethiopiques numéro 31" - révue socialiste de culture négro-africaine 3e trimestre, IFAN, (1982) [2] Template:Webarchive.</ref> and should not be confused with the mythical and sacred tree mbos―enshrined in Serer religion and Serer cosmogony―where the mbossé (the lizard) takes its name.

Due to confusion with the large New World lizards of the family Iguanidae, the lizards became known as "goannas" in Australia. Similarly, in South African English, they are referred to as leguaans, or likkewaans, from the Dutch term for the Iguanidae, leguanen.

DistributionEdit

The various species cover a vast area, occurring through Africa, the Indian subcontinent, to China, the Ryukyu Islands in southern Japan, south to Southeast Asia to Thailand, Malaysia, Brunei, Indonesia, the Philippines, New Guinea, Australia, and islands of the Indian Ocean and the South China Sea. They have also been introduced outside of their natural range, for instance, the West African Nile monitor is now found in South Florida.<ref>Template:Cite magazine</ref> Monitor lizards also occurred widely in Europe in the Neogene, with the last known remains in the region dating to the Middle Pleistocene.<ref>Template:Cite journal</ref>

Habits and dietEdit

Most monitor lizards are almost entirely carnivorous,<ref>Template:Cite book</ref> consuming prey as varied as insects, crustaceans, arachnids, myriapods, molluscs, fish, amphibians, reptiles, birds, and mammals. Most species feed on invertebrates as juveniles and shift to feeding on vertebrates as adults. Deer make up about 50% of the diet of adult Komodo dragons, the largest monitor species.<ref>Template:Cite book</ref> In contrast, three arboreal species from the Philippines, Varanus bitatawa, mabitang, and olivaceus, are primarily fruit eaters.<ref name="Greene">Template:Cite book</ref><ref name="Welton2010">Template:Cite journal</ref><ref>Template:Cite journal</ref>

BiologyEdit

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File:Varanoid skulls.png
Skulls of various varanoids

Monitor lizards are considered unique among animals in that its members are relatively morphologically conservative, yet show a very large size range.<ref name=pianka1995>Template:Cite journal</ref> However, finer morphological features such as the shape of the skull and limbs do vary, and are strongly related to the ecology of each species.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

Like snakes, monitor lizards have highly forked tongues that act as part of the "smell" sense, where the tips of the tongue carry molecules from the environment to the a sensory organ in the skull called the Jacobson's organ. The forked apparatus allows for these lizards to sense boundaries in the molecules they collect, almost smelling in "stereo".<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> While most reptiles possess taste buds, monitor lizards and likely snakes as well completely lack taste buds.<ref>Template:Cite journal</ref> Merten's water monitor, the most aquatically adapted monitor species, is uniquely capable of using its sense of smell underwater to locate and capture prey.<ref>Template:Cite journal</ref>

Monitor lizards are oviparous,<ref name="piankavitt2003" /> laying from seven to 38 eggs,<ref>https://indonesiaindonesia.com/f/37477-sejarah-pulau-komodo/ (in Indonesian)</ref> which they often cover with soil or protect in a hollow tree stump. Some species, including the Komodo dragon, are capable of parthenogenesis.<ref>Template:Cite journal</ref>

VenomEdit

Anatomical and molecular studies indicate that most if not all varanids are venomous.<ref name="Fry2009"> Template:Cite journal</ref><ref name="Fry2006"> Template:Cite journal</ref> Unlike snakes, monitor lizard venom glands are situated in their lower jaw.<ref>Template:Cite journal</ref> The venom of monitor lizards is diverse and complex, as a result of the diverse ecological niches monitor lizards occupy.<ref>Template:Cite journal</ref>

For example, many species have anticoagulant venom, disrupting clotting through a combination of fibrinogenolysis and blocking platelet aggregation. Amongst them, arboreal species, such as the tree monitors and the banded monitor, have by far the strongest fibrinogenolytic venom. As a result, wounds from monitor lizard bites often bleed more than they would if they were simply lacerations. Venom may also cause hypotension.<ref>Template:Cite journal</ref>

In some species such as the Komodo dragon and the desert monitor, venom also induces a powerful neurotoxic effect. In the latter species for instance, envenomation causes immediate paralysis in rodents (but not birds) and lesser effects of the same nature in humans.<ref>Template:Cite journal</ref>

MetabolismEdit

Monitor lizards maintain large territories and employ active-pursuit hunting techniques that are reminiscent of similar-sized mammals.<ref name="kinggreenknight1999">King, D., Green, B., Knight, F. (1999). Monitors: The Biology of Varanid Lizards. Florida. Krieger Publishing Company.</ref> The highly active nature of monitor lizards has led to numerous studies on the metabolic capacities of these lizards. The general consensus is that monitor lizards have the highest standard metabolic rates of all extant reptiles.<ref name="piankavitt2003">Pianka, E.R., Vitt, L.J. (2003). Lizards: Windows to the Evolution of Diversity. California. University of California Press.</ref>

Monitor lizards have a high aerobic scope<ref name=piankavitt2003 /><ref name=wood1978>Template:Cite journal</ref> that is afforded, in part, by their heart anatomy. Whereas most reptiles are considered to have three-chambered hearts, the hearts of monitor lizards – as with those of boas and pythons – have a well developed ventricular septum that completely separates the pulmonary and systemic sides of the circulatory system during systole.<ref name=wang2003>Template:Cite journal</ref> This allows monitor lizards to create mammalian-equivalent pressure differentials between the pulmonary and systemic circuits,<ref name=wang2003 /> which in turn ensure that oxygenated blood is quickly distributed to the body without also flooding the lungs with high-pressure blood.

IntelligenceEdit

Template:See also

At least some species of monitors are known to be able to count; studies feeding rock monitors varying numbers of snails showed that they can distinguish numbers up to six.<ref name="King2">King, Dennis & Green, Brian. 1999. Goannas: The Biology of Varanid Lizards. University of New South Wales Press. Template:ISBN, p. 43.</ref><ref name ="varanoid">Pianka, E.R.; King, D.R. and King, R.A. (2004). Varanoid Lizards of the World. Indiana University Press.</ref> Nile monitors have been observed to cooperate when foraging; one animal lures the female crocodile away from her nest, while the other opens the nest to feed on the eggs. The decoy then returns to also feed on the eggs.<ref name="King2"/><ref name="varanoid"/> Komodo dragons at the National Zoo in Washington, DC, recognize their keepers and seem to have distinct personalities.<ref name="varanoid"/> Blue and green tree monitors in British zoos have been observed shredding leaves, apparently as a form of play.<ref name=Kane2019>Template:Cite journal</ref>

Human usesEdit

As petsEdit

Monitor lizards have become a staple in the reptile pet trade. The most commonly kept monitors are the savannah monitor and Ackie dwarf monitor, due to their relatively small size, low cost, and relatively calm dispositions with regular handling.<ref name="Sprackland"/> Among others, black-throated, Timor, Asian water, Nile, mangrove, emerald tree, black tree, roughneck, Dumeril's, peach-throated, crocodile, and Argus monitors have been kept in captivity.<ref name="Sprackland"/>

Traditional medicinesEdit

Monitor lizards are poached in some South- and Southeast Asian countries, as their organs and fat are used in some traditional medicines, although there is no scientific evidence as to their effectiveness.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

File:Road kill lizard. India - Flickr - gailhampshire.jpg
A dead monitor in India, with its hemipenes removed. Monitor hemipenes are often trafficked and illegally sold.

The dried and dyed hemipenes of Bengal monitors, and less often yellow and water monitors, are frequently trafficked and illegally sold in India and online under the deceptive term 'Hatha Jodi', where it is claimed to be the root of a supposed rare Himalayan plant in order to fool buyers and retailers, and to disguise the trade from wildlife authorities. Sellers advertise 'Hatha Jodi' as having the tantric power to bring wealth, power and contentment. A pair of hemipenes may sell at a value of up to US$250.<ref>Template:Cite journal</ref> In India, the body oil of monitor lizards is sold for thousands of Indian rupees to residents in metropolitan cities as a treatment for rheumatism.<ref>Template:Cite journal</ref>

Monitor lizard meat, particularly the tongue and liver, is eaten in parts of India and Malaysia and is supposed to be an aphrodisiac.<ref name="Parameswaran2006">Template:Cite journal</ref><ref>Eating Biawak. The Malaysian Life (April 2009)</ref>

Consuming raw blood and flesh of monitor lizards has been reported to cause eosinophilic meningoencephalitis, as some monitors are hosts for the parasitic nematode Angiostrongylus cantonensis.<ref name="Parameswaran2006" />

LeatherEdit

"Large-scale exploitation" of monitor lizards is undertaken for their skins, which are described as being "of considerable utility" in the leather industry.Template:Cn In Papua New Guinea, monitor lizard leather is used for membranes in traditional drums (called kundu), and these lizards are referred to as kundu palai or "drum lizard" in Tok Pisin, the main Papuan trade language. Monitor lizard skins are prized in making the resonant part of serjas (Bodo folk sarangis) and dotaras (native strummed string instruments of Assam, Bengal and other eastern states). The leather is also used in making a Carnatic music percussion instrument called the kanjira.

FoodEdit

The meat of monitor lizards is eaten by some tribes in India,<ref>Template:Cite news</ref> Nepal,<ref>Template:Cite journal</ref> the Philippines, Australia, South Africa, and West Africa as a supplemental meat source.Template:Citation needed Both meat and eggs are also eaten in Southeast Asian countries such as Vietnam and Thailand as a delicacy.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}Template:Cbignore</ref>

ConservationEdit

According to IUCN Red List of threatened species, most of the monitor lizards species fall in the categories of least concern, but the population is decreasing globally. All but five species of monitor lizards are classified by the Convention on International Trade in Endangered Species of Wild Fauna and Flora under Appendix II, which is loosely defined as species that are not necessarily threatened with extinction but may become so unless trade in such species is subject to strict regulation to avoid use incompatible with the survival of the species in the wild. The remaining five species – the Bengal, yellow, desert, and clouded monitors and the Komodo Dragon– are classified under CITES Appendix I, which outlaws international commercial trade in the species.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

The yellow monitor is protected in all countries in its range except Bhutan, Nepal, India, Pakistan, and Bangladesh.<ref>Template:Cite journal</ref>

In Kerala, Andhra Pradesh, Karnataka, Telangana and all other parts of South India, catching or killing of monitor lizards is banned under the Protected Species Act.

EvolutionEdit

File:Varanus priscus Melbourne Museum.jpg
The giant extinct megalania (Varanus priscus)

Varanus is the only living genus of the family Varanidae. Varanids last shared a common ancestor with their closest living relatives, earless "monitors", during the Late Cretaceous. The oldest known varanids are from the Late Cretaceous of Mongolia. During the Eocene, the varanid Saniwa occurred in North America. The closest known relative of Varanus is Archaeovaranus from the Eocene of China, suggesting that the genus Varanus is of Asian origin. The oldest fossils of Varanus date to the early Miocene.<ref name=":02">Template:Cite journal</ref>

Many of the species within the various subgenera also form species complexes with each other:

Euprepriosaurus

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Odatria

Varanus

Polydaedalus

Empagusia

Soterosaurus

The tree monitors of the V. prasinus species complex (V. prasinus, V. beccarii, V. boehmei, V. bogerti, V. keithhornei, V. kordensis, V. macraei, V. reisingeri, V. telenesetes) were once in the subgenus Euprepriosaurus, but as of 2016, form their own subgenus Hapturosaurus.<ref name=":3">Template:Cite journal</ref>

V. jobiensis was once considered to be a member of the V. indicus species complex, but is now considered to represent its own species complex.<ref name=":3" />

Phylogeny as of Brennan et al. 2020 <ref>Template:Cite journal</ref>
File:Varanus phylogeny as of Brennan et al 2020 (UPDATE 5).jpg

TaxonomyEdit

Genus Varanus

Species marked with Template:Extinct are extinct

Subgenus Empagusia:

Subgenus Euprepiosaurus:<ref>Ziegler, Thomas; Schmitz, Andreas; Koch, Andre; 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. prasimus species groups". Zootaxa 1472: 1-28.</ref>

Subgenus Hapturosaurus:<ref name=":3" />

Subgenus Odatria:

Subgenus Papusaurus

Subgenus Philippinosaurus:

File:Monitor lizard in Kalahari.JPG
White-throated monitor (V. a. albigularis) on the Kalahari savannah

Subgenus Polydaedalus:

Subgenus Psammosaurus:

  • V. griseus, desert monitor
    • V. g. griseus, desert monitor, grey monitor
    • V. g. caspius, Caspian monitor
    • V. g. koniecznyi, Indian desert monitor, Thar desert monitor
  • V. nesterovi, Nesterov's desert monitor

Subgenus Solomonsaurus:<ref>Template:Cite journal</ref>

  • V. spinulosus, spiny-necked mangrove monitor, Solomon Islands spiny monitor

Subgenus Soterosaurus:

  • V. bangonorum, Bangon monitor<ref name="undercover-researchers">{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

  • V. cumingi, Cuming's water monitor, yellow-headed water monitor
  • V. dalubhasa, Enteng's monitor<ref name="undercover-researchers"/>
  • V. marmoratus, marbled water monitor, Philippine water monitor
  • V. nuchalis large-scaled water monitor
  • V. palawanensis, Palawan water monitor
  • V. rasmusseni<ref>Koch, André; Gaulke, Maren; Böhme, Wolfgang (2010). "Unravelling the underestimated diversity of Philippine water monitor Lizards (Squamata: Varanus salvator complex), with description of two new species and a new subspecies". Zootaxa 2446: 1-54. (Varanus rasmusseni, new species, p. 28).</ref><ref>Varanus rasmusseni, The Reptile Database</ref> Rasmussen's water monitor
  • V. rudicollis, black roughneck monitor
  • V. salvator, Asian water monitor
    • V. s. salvator, Sri Lankan water monitor
    • V. s. andamanensis, Andaman water monitor
    • V. s. bivittatus, two-striped water monitor, Javan water monitor
    • V. s. macromaculatus, Southeast Asian water monitor
    • V. s. ziegleri, Ziegler's water monitor
  • V. samarensis, Samar water monitor
  • V. togianus, Togian water monitor

Subgenus Varanus:

ReferencesEdit

Template:Reflist

Further readingEdit

  • Merrem B (1820). Versuchs eines Systems der Amphibien: Tentamen Systematis Amphibiorum. Marburg: J.C. Krieger. xv + 191 pp. + one plate. (Varanus, new genus, p. 58). (in German and Latin).

External linksEdit

Template:Varanoidea

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