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Varanus olivaceus HALLOWELL, 1857

IUCN Red List - Varanus olivaceus - Vulnerable, VU

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Higher TaxaVaranidae, Platynota, Anguimorpha, Sauria, Squamata (lizards) 
Common NamesE: Gray’s Monitor Lizard, Butaan
G: Butaan 
SynonymVaranus ornatus GRAY 1845: 10
Varanus olivaceus HALLOWELL 1857: 150
Varanus grayi BOULENGER 1885: 312
Varanus grayi — TAYLOR 1922: 145
Varanus (Philippinosaurus) grayi — MERTENS 1962
Varanus olivaceus — AUFFENBERG 1988
Varanus olivaceus — DE LISLE 1996: 131
Varanus (Philippinosaurus) olivaceus — BÖHME 2002
Varanus (Philippinosaurus) olivaceus — KOCH et al. 2013
Varanus (Philippinosaurus) olivaceus — BUCKLITSCH et al. 2016: 50 
DistributionPhilippines (S Luzon, Polillo), Catanduanes Islands, elevation max. 400 m.

Type locality: “Manilla”  
TypesHolotype: ANSP 9916, presumed lost (Pianka 2004b). 
CommentDE LISLE (1996: 131) erroneously cited a non-existing paper by HALLOWELL (1857) as original description. Varanus olivaceus is listed as a synonym of Varanus bengalensis bengalensis by MERTENS 1963:5.

V. olivaceus is one of two primarily herbivorous monitor lizards (in addition to V. mabitang).

This is a very rare, endangered species.

Habitat: rain forest, arboricolous

Max. total length: 176 cm, SVL 73 cm (males). 
  • Amer, Sayed A. M. and Yoshinori Kumazawa 2008. Timing of a mtDNA gene rearrangement and intercontinental dispersal of varanid lizards. Genes Genet. Syst. 83: 275–280
  • Auffenberg W 1988. Gray’s Monitor Lizard. Univ. Florida Press, Gainesville, 419 pp.
  • Auffenberg, W. 1976. First description of an adult Varanus grayi. Copeia 1976 (3): 586-588 - get paper here
  • BENNETT, DANIEL 2014. A Dubious Account of Breeding Varanus olivaceus in Captivity at the Paradise Reptile Zoo in Mindoro, Philippines Biawak 8 (1): 12 - get paper here
  • BENNETT, DANIEL 2014. The Use of an External Telemetric Device on Varanus olivaceus Biawak 8 (2): 66 - get paper here
  • BENNETT, DANIEL 2014. An Inexpensive, Non-intrusive, Repeatable Method for Surveying Frugivorous Monitor Lizards Biawak 8 (1): 31 - get paper here
  • BENNETT, DANIEL 2014. The Arboreal Foraging Behavior of the Frugivorous Monitor Lizard Varanus olivaceus on Polillo Island Biawak 8 (1): 15 - get paper here
  • BENNETT, DANIEL & TOM CLEMENTS 2014. The Use of Passive Infrared Camera Trapping Systems in the Study of Frugivorous Monitor Lizards Biawak 8 (1): 19 - get paper here
  • Böhme,W. 2003. Checklist of the living monitor lizards of the world (family Varanidae). Zoologische Verhandelingen 341: 6-43 - get paper here
  • Boulenger, G.A. 1885. Catalogue of the lizards in the British Museum (Natural History). Vol. 2, Second edition. London, xiii+497 pp. - get paper here
  • BUCKLITSCH, YANNICK; WOLFGANG BÖHME, ANDRÉ KOCH 2016. Scale Morphology and Micro-Structure of Monitor Lizards (Squamata: Varanidae: Varanus spp.) and their Allies: Implications for Systematics, Ecology, and Conservation. Zootaxa 4153 (1): 001–192
  • De Lisle, H.F. 1996. Natural History of Monitor Lizards. Krieger, Malabar (Florida)
  • Earley, Ryan L.; Omar Attum, Perri Eason 2002. Varanid combat: perspectives from game theory. Amphibia-Reptilia 23 (4): 469-485 - get paper here
  • FRÝDLOVÁ, PETRA and DANIEL FRYNTA 2010. A test of Rensch’s rule in varanid lizards. Biological Journal of the Linnean Society 100: 293–306 - get paper here
  • Gaulke, Maren 1991. Systematic relationships of the Philippine water monitors as compared with Varanus s. salvator, with a discussion of dispersal routes. Mertensiella 2: 154-167
  • Gojo-Cruz, Paul Henric P. and Leticia E. Afuang 2018. The Zoogeographic Significance of Caraballo Mountain Range, Luzon Island, Philippines With Focus on the Biogeography of Luzon’s Herpetofauna Philippine Journal of Science 147 (3): 393-409 - get paper here
  • Gray, J. E. 1845. Catalogue of the specimens of lizards in the collection of the British Museum. Trustees of die British Museum/Edward Newman, London: xxvii + 289 pp. - get paper here
  • Hallowell, EDWARD 1857. Notes on the reptiles in the collection of the museum of the Academy of Natural Sciences. Proc. Acad. Nat. Sci. Philadelphia, 8 (4): 146-153 [1856] - get paper here
  • Koch A, Ziegler T, Böhme W, Arida E, Auliya M. 2013. Pressing Problems: Distribution, Threats, and Conservation Status of the Monitor Lizards (Varanidae: Varanus spp.) of Southeast Asia and the Indo-Australian Archipelago. Herp. Cons. Biol. 8 (Monograph 3): 1 − 62. - get paper here
  • Lutz, M. 2006. Der Butaan (Varanus olivaceus), HALLOWELL 1856, Haltung und erste erfolgreiche Nachzucht im Terrarium. Sauria 28 (4): 5-13 - get paper here
  • MCLEOD, David S.; Cameron D. SILER, Arvin C. DIESMOS, Mae L. DIESMOS, Vhon S. GARCIA, Angela O. ARKONCEO, Kelvin L. BALAQUIT, Charlene C. UY, Mariden M. VILLASERAN, Earle C. YARRA, Rafe M. BROWN 2011. Amphibians and Reptiles of Luzon Island, V: The Herpetofauna of Angat Dam Watershed, Bulacan Province, Luzon Island, Philippines. Asian Herpetological Research 2 (4): 177–198 - get paper here
  • Mertens,R. 1962. Philippinosaurus, eine neue Untergattung von Varanus. Senckenbergiana biologica 43 (5): 331-333
  • Pianka, E. R. and D. R. King, eds. 2004. Varanoid Lizards of the World. Indiana University Press, 599 pp - get paper here
  • Sweeney, R.G., Sekscienski, S. & Maslanka, M. 2017. Nutritional analysis of natural fruit items consumed by Butaan (Varanus olivaceus) with comparison to commonly used captive dietary items. Herpetological Review 48 (4): 787-791 - get paper here
  • Taylor, E.H. 1922. The lizards of the Philippine Islands. Department of Agriculture and Natural Resources, Bureau of Science, Government of the Philippine Islands, Manila, Publication no. 17: 269 pp. - get paper here
  • Welton, Luke J.; Cameron D. Siler, Daniel Bennett, Arvin Diesmos, M. Roy Duya, Roldan Dugay, Edmund Leo B. Rico, Merlijn Van Weerd, and Rafe M. Brown 2010. A spectacular new Philippine monitor lizard reveals a hidden biogeographic boundary and a novel flagship species for conservation. Biology Letters doi:10.1098/rsbl.2010.0119 - get paper here
  • Yuyej, M.D. 2012. Husbandry and Reproduction of Varanus olivaceus Hallowell (Sauria:Varanidae) at the avilon Montalban Zoological Park. Biawak 6 (1): 39 - get paper here
  • Ziegler, Thomas; Böhme, Wolfgang 1996. Neue Erkenntnisse zur Geschlechtsunterscheidung bei squamaten Reptilien. Kleintierpraxis 41 (8): 585-590
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