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Dumeril's Monitor Print E-mail

Morphology

Maximum size claimed in the literature is 150cm (Sprackland 1976) but no specimens over 130cm seem to have been recorded in the wild. Healthy adult males maintained in captivity may weigh 3kg, females of 1m long (they may no grow larger than this) may weigh 2.3kg. Weights of wild animals may be lower than this. Hatchlings weigh around 17g and have body length of about 8cm (Radford and Paine 1989). After six months they may have grown to almost 30cm total length.Details of morphology and scalation can be found in (De Rooij 1915; Mertens 1942; Taylor 19**; Brandenberg 1983; Sprackland in press). Krebs (1979) reported that Dumeril's monitors are able to seal their nostrils when submerged, an adaptation that may be shared with other aquatic monitor lizards. Dumeril's monitor is often confused with the rough-necked monitor, e.g. Coburn's (1987) photograph of "V.rudicollis" is really V.dumerilii. The species can be distinguished mainly from the scales on the back of the neck, which are enlarged in both species, but raised and spiny in V.rudicollis and more or less flat in V.dumerilii.

Diet

The stomach contents of only four animals have been examined (Losos & Greene 19** & Brandenberg 1983); all contained crabs and one also contained a spider and an insect larva. Loveridge's (1962) claim that they eat birds needs verification. Raven (1946) records that they feed on the eggs of green turtles and Barbour (1921) that they eat ants. The ability of this lizard to feedon crabs is well documented in the literature. Krebs (1977) considered them to be specialised crab eaters, levering off the larger appendages, puncuring the shells with the needle-sharp, sparsely arranged teeth and swallowing them whole. Where crabs are absent the bulk of the diet may consist of insects collected on the forest floor (Auffenberg 19**).

Behaviour

The most intriging aspect of the biology of Dumeril's monitor lizard is the extraordinary colouration and pattern of the hatchlings which fades within weeks and changes to drab adult colouration within two months (first reported in Horn & Schulz 1977). More than one person has noticed the resemblance of the young lizards to hatchling king cobras. The pattern certainly looks like a mimic of a venomous or unpalatable animal and it is difficult to see how such colouration could serve as camouflage. Such talk is entirely speculative, because there have been no observations made on hatchlings in the wild. In captivity hatchlings may bury themselves or remain on branches above the ground. Both young and adult Dumeril's monitors are superb climbers and swimmers. Krebs (1979) reports that they can climb slippery telgraph poles with ease. According to Nutpand (no date) they are less active than other monitor species, spending most of their time sleeping in rock crevices and tree hollows. He suggests that they may habitually return to the same retreat after foraging. Smith (1930) records that they run into the sea to escape from dogs. Davis and Darling (1986) report ritual fighting between Dumeril's monitors in the manner typical for large varanids; opponents grip each other shoulders with the forefeet whilst standing bipedally using their tails as supports and attempt to push each other over. This behaviour is generally held to occur between male monitor lizards, but problems of sex identification make this an uncertain claim. Patterns of acivity in the wild are unknown. Sprackland (1976) reports that captives have two daily peaks of activity in mid morning and late afternoon. According to Radford and Paine (1989) captives in north America become less active from mid August until the end of September

Care in Captivity

In captivity this species should be provided with a very large enclosure that allowsthem to climb, dig and at lewast emerse themselves in water. Thermoregulatory behaviour of this species has not been studied, but many monitor lizards like to bask at tempetaures in excess of **oC and hot spots should be provided accordingly. There is some suggestion that the thermal preferences of the sexes may differ. There appears to be no sexual diamorphism, but males may recah a greater length and mass than females. A method of sexing Dumeril's monitors that involves the use of anaesthetics and fiberoptic laparoscopy is given by Davis and Phillips (1991). The only published report of breeding is Radford and Paine (1989). A pair housed apart in 150 X 130 X 270cm enclosures were fed on rodents, horsemeat, fish and dog "chow" with vitamin and mineral supplements were introduced to each other every August for six years. In the sixth year copulation occurred over three days and five weeks later 14 eggs were laid over eight days, of which five proved fertile. They were incubated at 26.7-30oC and hatched after 215-222 days. The hatchlings grew well on a diet of worms, crickets, catfood and parts of baby mice. Zimmerman (1986) gives an incubation time of 203-215 days at 28oC for eggs that were also laid in September.

According to Nutphand (no date) Dumeril's monitor is known as hao-chang-kao (white jungle monitor) in southern Thailand. In Malaysia it is sometimes known as biawak kudong (Harrison and Lim 1957).

APPENDIX.  LOCATION DATA FOR VARANUS DUMERILII

Kuala Teku, Peninsular Malaysia.     SMITH 1922.
Mergui Archipelago and coast of Mergui      SMITH 1930
Khao Chong, Trang.      TAYLOR
Kedah, Mallaka    SCORTECCI 1929
Tavoy SMITH 1932
Banjermasin    SCHLEGEL 1839
Batu MULLER & SCHLEGEL 1845
Mergui   BLYTHE 1853
Singawang   BLEEKER 1858
Deli, Sumatra    BOULENGER 1890
Indragiri, Sumatra. SCHENKEL 1901
Tenesserim ANNANDALE 1905.
Nanag Raoen, Fluss Howong    VAN LIDTH DE JEUDE 1905
Taluk, Sumatra     DE LAANG & DE ROOIJ 1905.
Bangka    BLEEKER 1860
Solok   MULLER 1887
Pulu Gallang, Rhiau Archipelago    CHASEN & SMEDLEY 1927
Borgon, Baram, Sangasanga, Lahat, Balikpanan Borneo; Sibolga, Bama Sumatra      SPRACKLAND 19**
Singapore   FEJERVARY 1935
Stabat Sumatra   BOETTGER 1893
Serdand, Talu, Baram, Kuching, Pangkalan, Ampat, Buntal, Mt Dulit, Rejank River, Akar River, Bogon, Howong River, Tandjong,  DE ROOIJ 1915.
Sampit, Borneo;  Banatng Kwis, Sumatra; Sungei Rampah, Sumatra; MERTENS 1942.
Rawang, Selangor; Penang Hill, below Belercteiro; Kota Tinggi, Johor, Malaysia         BENNETT (in prep)
Specimens examined from Sumatra (Deli, "east coast", Taloek, Serdang, Bangka, and Batoe) and Borneo (Balikpapan, Banjermasin and Nanga Raoen) (BRANDENBURG 1983).

AUFFENBERG,W. 1981. Behavioral ecology of the Komodo monitor. University of Florida, Gainesville.  or
AUFFENBERG,W. 1988. Gray's monitor lizard. University of Florida, Gainesville.
BARBOUR,T. 1921. Aquatic skinks and arboreal monitors. Copeia 1921 (1):42-44.
BENNETT,D. 1993. A review of some literature concerning the rough-necked monitor lizard Varanus rudicollis. Reptilian 1 (9):7-10.
BOULENGER,G.A. 1885. Catalogue of lizards in the British Museum (Natural History). Volume 2.
BRANDENBERG,T. 1983. Monitors in the Indo-Australian Archipelago. 1-121. E.J. Brill, Leide.
COBURN,J. 1987. Snakes and lizards. Their care and breeding in captivity, David and Charles, Newton Abbott.
DAVIS,R., DARLING,R. & DARLINGTON.A. 1986 Herpet. Rev.17(4):85-86. Ritualised Combat in captive V.dumerilli.
DAVIS,R.B. & PHILLIPS,L.G. 1991. Herp. Review 22(1):18-19. A method of sexing Dumeril's monitor, Varanus dumerili.
HARRISON, J.L. & BOO-LIAT,L. 1957. Monitors of Malaya. Malay. Nat. J. 12 (1):1-10.
HORN,H.G. & SCHULZ,B. 1977. Varanus dumerilii, wie ihn nicht jeder kennt. Das Aquarium 11 (9):37-38.
KREBS,U. 1979. Der Dumeril-Waran (Varanus dumerilii), ein spezialisierter Krabbenfresser? Salamandra 15 (3):146-157.
LEKAGUL,B. 1969. Monitors of Thailand. Conservation News of S.E. Asia. 8:31-32
LOSOS,J.B. & GREENE,H.W. 1988. Ecological and evolutionary implications of diet in monitor lizards. Biol. J. Linn. Soc. 35:379-407.
MERTENS,R. 1942. Die Familie der Waranae (Varanidae). Abh. Senck. Nat. Gesel. Abh. 462; 465; 466.
??MERTENS,R. 1959. Liste der Waren Asiens & der Indo-Australische inselwelt mit systematischen beobachtungen. Senck. Biol. 40: 221-240.
NUTPHAND,W. NO DATE. The monitors of Thailand. Mitphadung Publishing Office, Bangkok.
PITMAN,C.R.S. 1962. More snake and lizard predators of birds. Bull. British Ornith. Club. 82 (3):45-55.
RADFORD,L. & PAYNE,F.L. 1989. The reproduction and management of Varanus dumerilii. International Zoo Yearbook 28:153-155.
RAVEN,H.C. 1946. Predators eating green turtle eggs in the East Indies. Copeia 1946 (1):48.
DE ROOIJ, N. 1915. The reptiles of the Indo-Australian archipelago. E.J. Brill, Leiden.
SMITH,M. 1922. Reptiles and batrachians. Journal of the Federated Malay States 10:269.
SMITH,H.C. 1930. Monitor lizards of Burma. Journal Bombay Nat. Hist. Soc. 34:367-373.
TAYLOR,E.H. 1963. Lizards of Thailand. Univ. Kansas Sci. Bull. 44 (14).
SPRACKLAND,R. 1976. Notes on Dumeril's monitor lizard Varanus dumerili (Schlegel). Sarawak. Mus. J. 24 (45):287-291.
SPRACKLAND,R.G. In Press.The taxonomic status of the monitor lizard Varanus dumerilii heteropholis BOULENGER 1892. Sarawak Museum Journal.



 
 

 

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