Global invasive species database

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Common name
erebachi (Marovo), Pazifikwaran (German), regu (Roviana), kalabeck monitor (English), varan des indes (French), Indian monitor (English), Pacific monitor (English), Indian monitor lizard (English), mangrove monitor (English), sosi (Touo), ambon lizard (English), flower lizard (English), stillahavsvaran (Swedish), varano de manglar (Spanish), George's island monitor (English), varan des mangroves (French)
Synonym
Monitor chlorostigma
Monitor douarrha
Monitor kalabeck
Tupinambis indicus
Varanus guttatus
Varanus tsukamotoi
Monitor doreanus
Monitor indicus
Varanus chlorostigma
Varanus indicus indicus
Varanus leucostigma
Varanus indicus kalabecki
Varanus indicus spinulosis
Similar species
Varanus doreanus, Varanus indicus spinulosus
Summary
Varanus indicus (mangrove monitor) is a terrestrial-arboreal monitor lizard that has been introduced to several locations for its meat, skin or as a biological control agent. It has created a nuisance on many islands preying on domesticated chickens and scavenging the eggs of endangered sea turtles. Bufo marinus (cane toad) was introduced to control mangrove monitor populations in several locations, but this has led to devastating consequences. In many places both of these species are now serious pests, with little potential for successful control.
Species Description
Varanus indicus (mangrove monitor) is darkly coloured with small yellow spots. It has a long, narrow head attached to a long neck. It has four strong legs, each with five sharp claws. The tail of V. indicus is very strong and highly compressed. Large scales cover the face, giving it a glassy appearance, while the rest of the body has oval-shaped, keeled scales. (HJHS, undated). V. indicus can weigh between 500g and 1900g, while reaching lengths between 50cm and 200cm. Males are much larger than females. (Bennett, 1995) V. indicus has a dark drown iris with a golden ring around it. It has an exceptional ability to enlarge its mouth significantly by spreading its hyoid apparatus and dropping its lower jaw for large prey consumption. The mouth is outlined in red, a result of blood mixed with saliva, which may frighten predators or attract prey, similar to Komodo dragons. \"The teeth are serrated along their anterior and posterior edges with the dentary teeth directed slightly laterally and the maxilliary teeth directed vertically.\" V. indicus has taste buds on the roof of the mouth and the tongue is frequently protruded, functioning as a chemical sensor. (HJHS, undated). V. indicus can live to be 15 years old. (Brook et al, 2004).
Notes
Varanus indicus (mangrove monitor) can have parasitic nematodes (round worms) on their body (Greer, 2006). They are very shy animals and are wary of humans when accustomed to human habitation. (HJHS, undated). In captivity, males are more aggressive than females. Instead of biting when threatened, V. indicus will defecate on an attacker. Nocturnal nesting has been reported for V. indicus while in captivity. (Greer, 2006). V. indicus is said to be a protected species in Indonesia. (Bennett, 1995).
Lifecycle Stages
The eggs of Varanus indicus (mangrove monitors) are 3.5-5cm in length, oblong and white, and take approximately 7-8 months to hatch. No parental care is given to the young when they hatch. (HJHS, undated).
Uses
The skin of Varanus indicus (mangrove monitors) is used on ceremonial drums and as leather (Bennett, 1995). V. indicus was introduced to Micronesia during the Japanese occupation as a food source and for rat population control (Buden, 2000). V. indicus was popular in the international pet trade in the late 1970's and early 1980's. In 1980, 13,000 mangrove monitors were traded around the world (Bennett, 1995).
Habitat Description
Varanus indicus (mangrove monitors) are tropical reptiles that can be found in mangroves, forests, swamps, and rainforests. They are most often found close to a water source. They prefer open areas to thick forests and have the capability to climb with great agility, dive, swim, and jump from high places. They have also been known to dig quite efficiently. In some areas they spend most of their time in the water, resting or looking for food. V. indicus may also take shelter in a tree, under a rock, in the hollow of a log or branch, or seldom in higher elevations and dry regions. In captivity they prey on fish but have no problem catching fish in deep water when not in captivity. (Bennett, 1995). Brook et al (2004) reports that V. indicus occupies/forages mainly around back swamps and paleochannels of floodplain. A male mangrove monitor has a home range of .4ha, while the female has a range of .9ha. (Bennett, 1995)
Reproduction
Male Varanus indicus fight for females prior to courtship. (HJHS, undated). Males in combat are upright, in a grappling/dancing posture. (Uetz, 1996) Male V. indicus mount the females during copulation and orient themselves head to head with their mate. The pair then travel 360° in a slow rotation, the male remaining on top of the female. After copulation, male mangrove monitors will rub the dorsum of female monitor's head and forequarters with their chin. Female mangrove monitors are smaller than most varanids, and therefore yield a smaller clutch size, between 2-12 eggs. (HJHS, undated). When food is abundant, V. indicus may reproduce quickly, producing a large number of small clutches. (Brook et al, 2004). In New Guinea, recently hatched specimens have been collected every month of the year. (Bennett, 1995). Ovarian mass is greater during the dry season for females. Male mangrove monitors have testicular sperm all year round and their fat body mass does not differ between seasons, unlike females who have higher fat contents during the dry season, mainly for egg production. (HJHS, undated).
Nutrition
Varanus indicus (mangrove monitor) is a carnivorous, terrestrial-arboreal predator (Uetz, 1996) that primarily feeds on snails, carrion (rotting eggs), (Greer, 2006), piglets (Buden, 2000), frogs, lizards, crabs, fish, insects, birds and their eggs, and other reptilian eggs. (Brook et al, 2004). A study was conducted in Guam that provided a specific breakdown of V. indicus's diet over three years. The study found that V. indicus ate 45% arthropods, 27.2% scincid and gekkonid lizards and their eggs, 13.6% terrestrial crabs, 9.1% rats and 4.5% Brahminy blind snakes. HJHS (undated) reports that, in urban settings the diet of V. indicus consisted of domesticated chickens and their eggs, squid (from fishing bait) and aluminum butter wrappers. As an opportunistic feeder, V. indicus can change its prey class based on abundance or availability, allowing it to adapt to many habitats. (HJHS, undated).
Pathway
Varanus indicus (mangrove monitor) was introduced to the island of Kosrae in Micronesia for ant control. (Howarth, 1990)In 1980, 13,000 Varanus indicus (mangrove monitors) were traded around the world. (Bennett, 1995).

Principal source: Bennett, D. 1995. A Little Book of Monitor Lizards. Viper Press, Aberdeen, U.K.

Compiler: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)

Review:

Publication date: 2007-01-09

Recommended citation: Global Invasive Species Database (2020) Species profile: Varanus indicus. Downloaded from http://www.iucngisd.org/gisd/species.php?sc=1065 on 14-08-2020.

General Impacts
Varanus indicus (mangrove monitor) feeds on domesticated chickens and their eggs in many locations where it has been introduced. (Bennett, 1995). On Tetepare Island in the Western Province of the Solomon Islands, V. indicus is known to scavenge the nests of turtles, including the endangered leatherback sea turtle (see Dermochelys coriacea in IUCN Red List of Threatened Species) (Read & Mosby, 2006).
Management Info
Biological: Varanus indicus (mangrove monitor) was introduced to the island of Kosrae in Micronesia for ant control. Populations grew significantly, and the country introduced Bufo marinus to regulate the burgeoning populations of V. indicus. Now both species exist on the island and are considered pests. (Howarth, 1990). A similar situation occured on the Marshall Islands as V. indicus was introduced prior to World War 2, probably for their skins, food and rat control. V. indicus began raiding chicken houses and their numbers increased drastically. Bufo marinus was introduced to regulate the lizard population. As populations of V. indicus dropped, the rat populations on the island rose. Bufo marinus was similarily introduced to Palau Island for mangrove monitor control. Lizard popluations declined on Palau but an increase was evident in the population of beetles known to be a major coconut pest. (Bennett, 1995)

Physical: V. indicus is seen as a threat to domesticated fowl and is trapped, poisoned, or killed near developed or agricultural areas. (HJHS, undated).

Countries (or multi-country features) with distribution records for Varanus indicus
Informations on Varanus indicus has been recorded for the following locations. Click on the name for additional informations.
Lorem Ipsum
Location Status Invasiveness Occurrence Source
Details of Varanus indicus in information
Status
Invasiveness
Arrival date
Occurrence
Source
Introduction
Species notes for this location
Location note
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Impact
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Impact information
Varanus indicus (mangrove monitor) feeds on domesticated chickens and their eggs in many locations where it has been introduced. (Bennett, 1995). On Tetepare Island in the Western Province of the Solomon Islands, V. indicus is known to scavenge the nests of turtles, including the endangered leatherback sea turtle (see Dermochelys coriacea in IUCN Red List of Threatened Species) (Read & Mosby, 2006).
Red List assessed species 0:
Locations
NORTHERN MARIANA ISLANDS
Mechanism
[1] Predation
Outcomes
[1] Socio-Economic
  • [1] Reduce/damage livestock and products
Management information
Biological: Varanus indicus (mangrove monitor) was introduced to the island of Kosrae in Micronesia for ant control. Populations grew significantly, and the country introduced Bufo marinus to regulate the burgeoning populations of V. indicus. Now both species exist on the island and are considered pests. (Howarth, 1990). A similar situation occured on the Marshall Islands as V. indicus was introduced prior to World War 2, probably for their skins, food and rat control. V. indicus began raiding chicken houses and their numbers increased drastically. Bufo marinus was introduced to regulate the lizard population. As populations of V. indicus dropped, the rat populations on the island rose. Bufo marinus was similarily introduced to Palau Island for mangrove monitor control. Lizard popluations declined on Palau but an increase was evident in the population of beetles known to be a major coconut pest. (Bennett, 1995)

Physical: V. indicus is seen as a threat to domesticated fowl and is trapped, poisoned, or killed near developed or agricultural areas. (HJHS, undated).

Locations
GUAM
PALAU
Management Category
Unknown
Bibliography
17 references found for Varanus indicus

Managment information
Bennett, D. 1995. A Little Book of Monitor Lizards. Viper Press, Aberdeen, U.K.
Brook, B., Whitehead, P., & J. Dingle. 2004. Potential cane toad short to medium term control techniques-the biological feasibility and cost of exclusion as a mitigation control strategy. Commonwealth of Australia.
Summary: Describes the impacts of cane toad on islands and native fauna.
Howarth, F. 1990. Environmental Impacts Classical Biological Control. Annu. Rev. Entomol. 1991. 36:485-509
Summary: This site provided some management information.
Mauldin, Richard E. and Peter J. Savarie, 2010. Acetaminophen as an oral toxicant for Nile monitor lizards (Varanus niloticus) and Burmese pythons (Python molurus bivittatus) Wildlife Research 37(3) 2010 215�222
Read, J. & K. Moseby. 2006. Vertebrates of Tetepare Island, Solomon Islands. Pacific Science (2006), vol. 60, no. 1:69�79
Summary: This report provided detailed information about V. indicus s presence on Tetepare Island.
Available from: http://muse.jhu.edu/journals/pacific_science/v060/60.1read.pdf [Accessed 13 December 2006]
Sarti Martinez, A.L. 2000. Dermochelys coriacea. In: IUCN 2007. 2007 IUCN Red List of Threatened Species. http://www.iucnredlist.org/search/details.php/6494/all
Summary: Available from: http://www.iucnredlist.org/search/details.php/6494/all [Accessed 11 February 2008]
General information
Bergman, D., Chandler, M., & A. Locklear. 1999. The Economic Impact of Invasive Species to Wildlife Services Cooperators. Human Conflicts with Wildlife: Economic Considerations.
Summary: This site described Guam s request for subsidization to aid in the control of V. indicus on Guam.
Available from: http://www.aphis.usda.gov/wildlife_damage/nwrc/symposia/economics_symposium/bergmanHR.pdf [Accessed 8 February 2008]
Buden, D. 2000. The Reptiles of Pohnpei, Federated States of Micronesia. Micronesica 32(2):155-180, 2000
Summary: This report gives information regarding diet, distribution, and basic characteristics.
Greer, A.E. 2006. Encyclopedia of Australian Reptiles. Australian Museum Online
Summary: Summarizes information about Australia s reptiles.
Available from: http://www.amonline.net.au/herpetology/research/pdf/varanidae.pdf [Accessed 11 December 2006]
Hopwood Junior High School. Undated. Mangrove Monitor Lizard. Commonwealth of the Norther Mariana Islands Public Scools System.
Summary: This site provides very useful information that spans life history through introductions. It is a very informative resource for V. indicus.
Available from: http://www.pss.cnmi.mp/Hopwood/index.cfm?pageID=24 [Accessed 14 December 2006]
ITIS (Integrated Taxonomic Information System). 2006. Online Database Varanus indicus.
Summary: An online database that provides taxonomic information, common names, synonyms and geographical jurisdiction of a species. In addition links are provided to retrieve biological records and collection information from the Global Biodiversity Information Facility (GBIF) Data Portal and bioscience articles from BioOne journals.
Available from: http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=174116 [Accessed 10 December 2006]
Perry, G., Rodda, G., Fritts, T., & T. Sharp. 1998. The lizard fauna of Guam s fringing islets: island biogeography, phylogenetic history and conservation implications. Global ecology and biogeography letters 7, 353-365.
Summary: Gives information about Guam s islets and the evidence of V. indicus on those islets.
Reed, R., Morton, J., & G. Desy. 2000. Use of Monofilament Snare Traps for Capture of Varanid Lizards. Micronesica 33(1/2):99-104, 2000
Summary: This report discusses the trapping of V. indicus and provides a brief description of its general description.
Reptiles Database, 2010. Varanus indicus Daudin, 1802
Summary: Available from: http://reptile-database.reptarium.cz/species.php?genus=Varanus&species=indicus [Accessed September 8 2010]
Uetz, P. 1996. Family Varanidae (Monitor Lizards). EMBL Reptile Database.
Summary: Available from: http://www.jcvi.org/reptiles/families/varanidae.php [Accessed 12 March 2010]
UNEP-WCMC. 12 December, 2006. UNEP-WCMC Species Database: CITES-Listed Species Varanus indicus
Summary: Provides synonyms, common names, and some basic information concerning V. indicus.
Available from: http://sea.unep-wcmc.org/isdb/CITES/Taxonomy/tax-species-result.cfm?displaylanguage=eng&source=animals&Genus=Varanus&Species=indicus&Country=&tabname=names [Accessed 9 December 2006]
Yuwono. 1997. Varanus doreanus The Blue-tailed Monitor. Herpetology of Indonesia.
Summary: Provides information about a recently rediscovered species that is closely related to the mangrove monitor.
Contact
The following 1 contacts offer information an advice on Varanus indicus
Buden,
Don
Organization:
Division of Natural Sciences and Mathematics College of Micronesia-FSM
Address:
P.O. Box 159 Kolonia, Pohnpei FM 96941
Phone:
691-320-2480 Ext 214
Fax:
691-320-2479
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