Monitor lizard

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Monitor lizards
Rock monitor (Varanus albigularis)
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Subphylum:Vertebrata
Class:Reptilia
Order:Squamata
Suborder:Scleroglossa
Infraorder:Anguimorpha
Superfamily:Varanoidea
Family:Varanidae
Genus:Varanus
Merrem, 1820
Species
Over 70, see text
 
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Monitor lizards
Rock monitor (Varanus albigularis)
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Subphylum:Vertebrata
Class:Reptilia
Order:Squamata
Suborder:Scleroglossa
Infraorder:Anguimorpha
Superfamily:Varanoidea
Family:Varanidae
Genus:Varanus
Merrem, 1820
Species
Over 70, see text

Monitor lizards are generally large lizards, although some can be as small as 20 cm (7.9 in) in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known. While most monitor lizards are carnivorous, three arboreal species, Varanus bitatawa, Varanus mabitang, and Varanus olivaceus, are primarily frugivores.[1][2] They are oviparous, laying from seven to 37 eggs, which they often cover with soil or protect in a hollow tree stump.[3]

Distribution[edit]

The various species of Varanus cover a vast area, occurring through Africa, the Indian Subcontinent, to China, down Southeast Asia to Indonesia, the Philippines, New Guinea, Australia and islands of the Indian Ocean, and the South China Sea. A large concentration of monitor lizards occurs on Tioman Island in the Malaysian state of Pahang. Some are now found in South Florida, particularly in the Everglades, where they are becoming a dangerous threat to cattle and to other wildlife, including even alligators.

Evolution[edit]

The giant extinct Varanus priscus

Monitor lizards differ greatly from other lizards in several ways, possessing a relatively high metabolic rate for reptiles, and several sensory adaptations that benefit the hunting of live prey. Recent research indicates the varanid lizards may have some venom.[4] This discovery of venom in monitor lizards, as well as in agamid lizards, led to the Toxicofera hypothesis: that all venomous lizards and snakes share a common venomous ancestor.[5]

During the late Cretaceous era, monitor lizards or their close relatives are believed to have evolved into amphibious and then fully marine forms, the mosasaurs, which reached lengths of up to 17 m.

Snakes were believed to be more closely related to monitor lizards than any other type of extant reptile; however, it has been more recently proposed that snakes are the sister group of the clade of iguanians and anguimorphs.[5]

During the Pleistocene epoch, giant monitor lizards lived in Southeast Asia and Australasia, the best known fossil being the megalania (Varanus priscus unless it falls in its own genus, in which case it is Megalania prisca). This species is an iconic member of the Pleistocene megafauna of Australia.

Some monitor lizards, including the Komodo dragon, are capable of parthenogenesis.[6]

Etymology[edit]

The generic name Varanus is derived from the Arabic word waral ورل, (alternative word waran). The name comes from a common Semitic root ouran, waran, or waral, meaning "lizard".[7] The occasional habit of varanids to stand on their two hind legs and to appear to "monitor" their surroundings has been suggested to have led to this name, as it was Latinized into Varanus. Its common name is derived from the Latin word monere meaning "to warn".[7]

In Austronesia where varanids are common, they are known under a large number of local names. They are usually known as biawak (Malay and Indonesian), bayawak (Filipino), binjawak or minjawak (Javanese), or variations thereof. Other names include hokai (Solomon Islands), bwo or puo (Maluku), halo (Cebu), galuf of kaluf (Micronesia and the Caroline Islands), batua or butaan (Luzon), alu (Bali), hora or ghora (Komodo group of islands), and guibang (Manobo).[8][9]

In Tamil and Malayalam, monitor lizards are known as udumbu, ghorpad घोरपड in Marathi, uda in Kannada, in Sinhalese as kabaragoya, in Telugu as udumu, in Punjabi and Magahi (and other Bihari languages) as goh, in Assamese as gui xaap, and in Bengali as goshaap or guishaap. Due to confusion with the large New World lizards of the family Iguanidae, the lizards became known as "goannas" in Australia. Similarly, in South Africa, they are referred to as leguaan, or likkewaan from the Dutch for iguana. The generic name inspired the name of the Japanese movie monster Varan.

Intelligence[edit]

Varanid lizards are very intelligent, and some species can even count.[10] Careful studies feeding V. albigularis at the San Diego Zoo varying numbers of snails showed they can distinguish numbers up to six.[10][11] V. niloticus lizards have been observed to cooperate when foraging.[10] One varanid lures the female crocodile away from her nest, while the other opens the nest to feed on the eggs.[10] The decoy then returns to also feed on the eggs.[10][11] Komodo dragons, V. komodoensis, at the National Zoo in Washington, D.C., recognize their keepers and seem to have distinct personalities.[11]

In captivity[edit]

Injured Bengal monitor being nursed at the Lok Biradari Prakalp in India

Monitor lizards have become a staple in the reptile pet trade. The most commonly kept monitors are the savannah monitor and Ackies monitor, due to their relatively small size, low cost, and relatively calm dispositions with regular handling.[7] Black throated monitors, white throated monitors, water monitors, Nile monitors, mangrove monitors, emerald tree monitors, black tree monitors, acanthurus monitors, quince monitors, crocodile monitors and Komodo dragons have been kept in captivity.[7] Like all reptiles kept as pets, monitors need an appropriately sized enclosure, hiding places, and an appropriate substrate.[7] Some water monitors also need a large water dish in which they can soak their entire bodies.[7] In the wild, monitors will eat anything they can overpower, but crickets, superworms, feeder fish, and the occasional rodent (for calcium) make up most of the smaller captive monitors' diets. Boiled eggs, silkworms, and earthworms can also be fed to them.[7] Larger species, such as Nile monitors, Asian water monitors, crocodile monitors, perenties, and Komodo dragons, will eventually require larger prey. Paleontologist and biology professor at Temple University, Michael Balsai has observed V. prasinus eating fruit in captivity, as has herpetologist and author, Robert G. Sprackland.[7][12]

Uses[edit]

Medicinal[edit]

Monitor lizard meat, particularly the tongue and liver, is eaten in parts of southern India and Malaysia an aphrodisiac.[13][14]

In parts of Pakistan, different parts of monitor lizards are used for a variety of medical purposes. The flesh is eaten for relief of rheumatic pain, abdominal fat is used as a salve for skin infections, oil and fat are used to treat hemorrhoids or chronic pain, and the oil is used as an aphrodesiac lubricant.[15]

Leather[edit]

"Large scale exploitation" of monitor lizards is undertaken for their skins, which are described as being "of considerable utility" in the leather industry.[15]

Food[edit]

The meat of monitor lizards are eaten by some tribes in Pakistan,[15] and in West Africa as a supplemental meat source.[citation needed]

Spiritual[edit]

The reproductive organs of monitor lizards are used in "black magic" in parts of Pakistan.[15]

Protected status[edit]

All but five species of monitor lizard 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 order to avoid use incompatible with the survival of the species in the wild. The remaining five species - V. bengalensis, V. flavescens, V. griseus, V. komodoensis, and V. nebulosus - are classified under CITES Appendix I, which outlaws international commercial trade in the species.[16]

In Tamil Nadu and all other parts of South India, catching or killing of monitor lizards is banned under the Protected Species Act.

Classification[edit]

V. bengalensis, Bengal monitor
V. timorensis, Timor tree monitor
V. salvadorii, crocodile monitor
White-throated monitor on the Kalahari savannah
Asian water monitor (Varanus salvator salvator)
Perentie (Varanus giganteus)
Mertens' water monitor (Varanus mertensi) seen at the Australia Zoo

Genus Varanus

Subgenus Empagusia:

Subgenus Euprepiosaurus:

Varanus macraei, blue-spotted tree monitor

Subgenus Odatria:

Subgenus Papusaurus:

Subgenus Philippinosaurus:

Subgenus Polydaedalus:

Subgenus Psammosaurus:

Subgenus Soterosaurus:


Subgenus Varaneades:

Subgenus Varanus:

Unassigned species:

References[edit]

  1. ^ Greene, Harry W. (1986). Diet and Arboreality in the Emerald Monitor, Varanus Prasinus, with Comments on the Study of Adaptation. Chicago: Field Museum of Natural History. OCLC 14915452. Retrieved 12 December 2013. 
  2. ^ Welton, L. J.; Siler, C. D.; Bennett, D.; Diesmos, A.; Duya, M. R.; Dugay, R.; Rico, E. L. B.; Van Weerd, M. et al. (2010). "A spectacular new Philippine monitor lizard reveals a hidden biogeographic boundary and a novel flagship species for conservation". Biology Letters 6 (5): 654–658. doi:10.1098/rsbl.2010.0119. ISSN 1744-9561. 
  3. ^ Bauer, Aaron M. (1998). Cogger, H.G. & Zweifel, R.G., ed. Encyclopedia of Reptiles and Amphibians. San Diego: Academic Press. pp. 157–159. ISBN 0-12-178560-2. 
  4. ^ Fry, B.G.; Wroe, S; Teeuwisse, W; van Osch, JP; Moreno, K; Ingle, J; McHenry, C; Ferrara, T; Clausen, P; Scheib, H; Winter, KL; Greisman, L; Roelants, K; van der Weerd, L; Clemente, CJ; Giannakis, E; Hodgson, WC; Luz, S; Martelli, P; Krishnasamy, K; Kochva, E; Kwok, HF; Scanlon, D; Karas, J; Citron, DM; Goldstein, EJC; Mcnaughtan, JE; Norman JA. (June 2009). "A central role for venom in predation by Varanus komodoensis (Komodo dragon) and the extinct giant Varanus (Megalania) priscus.". PNAS 106 (22): 8969–8974. doi:10.1073/pnas.0810883106. PMC 2690028. PMID 19451641. 
  5. ^ a b Fry, B.G.; Vidal, N; Norman J.A.; Vonk F.J.; Scheib, H.; Ramjan S.F.R; Kuruppu S.; Fung, K.; Hedges, B.; Richardson M.K.; Hodgson, W.C.; Ignjatovic, V.; Summerhays, R.; Kochva, E. (February 2006). "Early evolution of the venom system in lizards and snakes" (PDF). Nature 439 (7076): 584–588. doi:10.1038/nature04328. PMID 16292255. 
  6. ^ Smith, Kerri. "Dragon virgin births startle zoo keepers". Nature. Retrieved 2006-12-20. 
  7. ^ a b c d e f g h Robert George Sprackland (1992). Giant lizards. Neptune, NJ: T.F.H. Publications. p. 61. ISBN 0-86622-634-6. 
  8. ^ Mark K. Bayless (2004). "The local names of Pacific monitor lizards (Sauria: Varanidae) of Oceania & Indo-Malaysia, excluding Australia". Micronesia 37 (1): 49–55. 
  9. ^ Maren Gaulke (1992). "Taxonomy and biology of Philippine water monitors (Varanus salvator)". The Philippine Journal of Science 121 (4): 345–381. 
  10. ^ a b c d e King, Dennis & Green, Brian. 1999. Goannas: The Biology of Varanid Lizards. University of New South Wales Press. ISBN 0-86840-456-X, p. 43.
  11. ^ a b c Pianka, E.R.; King, D.R. and King, R.A. 2004. Varanoid Lizards of the World. Indiana University Press.
  12. ^ Balsai, Michael (1997). The General Care and Maintenance of Popular Monitors and Tegus. BowTie. p. 6. ISBN 978-1-882770-39-7. 
  13. ^ Parameswaran, K (2006). "Case series of eosinophilic meningoencephalitis from South India". Annals of Indian Academy of Neurology 9 (4): 217–222. doi:10.4103/0972-2327.29203. ISSN 0972-2327. Retrieved 12 December 2013. 
  14. ^ http://themalaysianlife.blogspot.com/2009/04/eating-biawak.html
  15. ^ a b c d Hashmi, M. Usman Ali; Khan, M. Zaheer; Amtyaz; Huda, Nawaz Ul. "Current Status, Distribution and Threats of Varanus Species (Varanus bengalensis & Varanus griseus) in Karachi & Thatta of Sindh". International Journal of Fauna and Biological Studies (AkiNik Publications) 1 (1): 34–38. ISSN 2347-2677. Retrieved 12 December 2013. 
  16. ^ "Identification Guides for Wildlife Traded in Southeast Asia". ASEAN-WEN. 2008. 
  17. ^ Varanus keithhornei, The Reptile Database
  18. ^ Mappress.com
  19. ^ Varanus prasinus, The Reptile Database
  20. ^ Varanus baritji, The Reptile Database
  21. ^ Varanus spinulosus, The Reptile Database

External links[edit]