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Varanus gouldii Print E-mail
Gould's goanna

Extract from A Little Book of Monitor Lizards © D. Bennett 1995. Viper Press, UK

(See notes on taxonomy under V.flavirufus)
Varanus panoptes panoptes   Storr 1980
Varanus panoptes rubidus    Storr 1980
Varanus panoptes horni      Bohme 1988

Note: Update to taxonomy 2001: Internation Comission for Zoological Nomeclature ruled that the revised names mentioned here should be abandoned.

At present three subspecies are recognised; V.panoptes panoptes inhabits the extreme north of eastern Western Australia and the Northern Territory, the islands of the Torres Straits and probably many other islands off the northern coast and V.panoptes horni is found in southern New Guinea. Records of Varanus gouldii on the islands of the Torres Straits and many other islands off the northern coast probably represent V.panoptes, but it is unclear whether they show more resemblance to V. p. panoptes or V.p.horni. An isolated race, V.p. rubidus, exists in central Western Australia. Animals from the north of Australia and New Guinea have a banded tail tip and more midbody scale rows than V.gouldii (192-242 vs. 132-189). The animals from New Guinea have 170-205 midbody scale rows, but otherwise there do not appear to be any distinguishing morphological characters. V.p.rubidus has a plain tail tip and mainland forms have 195-223 midbody scale rows. Island populations (i.e. from Dolphin Island) have as few as 176 scales rows. In pattern V.panoptes differs from V.flavirufus by possessing well defined pale and dark spots, usually arranged in rows over the back (Storr 1980; Bohme 1988).

The range of this species may be much greater than is suggested by the current literature. Schmida (1985) notes that specimens of "V.gouldii" in the Sydney sandstone region are darkly coloured with ten rows of yellow spots on the back and have a banded tail tip. At present the diagnostic characteristics used to distinguish between V.panoptes and V.gouldii do not appear to be 100% reliable. Comparisons of animals from throughout Australia, both from a morphological and biochemical perspective, are needed before the taxonomy of this group can be revised satisfactorily.  Some additional information on this group of monitors can be found in Grundke & Grundke (1992b).

Varanus panoptes is a mighty lizard. They are heavily built, powerful and fearless creatures that often adopt a bipedal stance, either in response to a threat or to gain a better vantage point (e.g. Barbour 1943). They have very powerful front limbs and frequent areas of tightly-packed sand and clay.

Virtually nothing is known of the way of life of the New Guinea subspecies gouldii horni. Bohme (1988) suggest a maximum size of at least 140cm TL and records the following locations; Teluk Berau, Gelib, Maerauke, Koerik, Bensbach, Port Moresby, Aroma and Yule Island and suggests that they may be found throughout the grasslands of southern New Guinea. Whitaker et al (1982) record it only from Western and Central Province in Papua New Guinea. Parker (1970) claims that this lizard was once common around Port Moresby but latterly  survived only on a few nearby islands (including Loloata and Motupuri).

In the north of Australia V.p.panoptes appears to be particularly associated with the vicinity of rivers. Shine (1986) rarely found them more than 200m from water and Stammer (1970) is probably referring to this goanna when he describes the river goanna, which digs holes in the banks of dry rivers and creeks. Similarly Cogger's (1981) report that a race in Arhemland inhabit mangroves, tidal flats, floodplains and sandstone escarpments may well refer to V.panoptes. Around Jabiru in the Northern Territory their usual foods are small mammals, other reptiles (skinks, agamids, varanids and snakes) and their eggs,  frogs, crabs and birds, as well as the obligatory  orthopterans and lepidopterans.  They have also been seen to congregate around fish kills. Wilson (1987) photographed a specimen digging up tortoise eggs besides a small river in Western Australia. Koch (1970) records that V.panoptes eats large scorpions. Around Jaribu adult males can attain weights as great as 4000g and reach lengths of up to 67cm SVL. In contrast females tend to weigh only one-third as much as males and none larger than 43cm SVL were found. Up to 13 eggs may be laid in a single clutch. Most breeding probably occurs during the wet season; presumed courtship was seen in July (Shine 1986). Hatchlings measure about 10.5cm SVL. Christain et al. (1995) compare the activity patterns and energetics of V. panoptes and V.gouldii in Kakadu National Park, Northern Territory. Here too V.gouldii is found close to water, where the greater availablity of food allows them to be active for more of the dry season than woodland-dwelling V. panoptes and V.gouldii , who spend about 5 months below ground at this time.
 
Little is known of the ecology of V. panoptes rubidus. Bodies of water are absent from most of its range. Like the nominate race they appear to favour harder substrates than Gould's goanna. At Wanjarri, an abandoned cattle station in Western Australia, they dig deep (130cm) burrows in ground packed rock-hard by thousands of hooves. When I visited in 1990 a drought had caused a mass die-off of kangaroos and the ground was littered with corpses in various states of decay and large numbers of kangaroos on the verge of death. Bloated goannas were feasting on the flesh of a particularly foul, putrid smelling and maggot-ridden corpse, tearing off chunks of rotten flesh with the forelimbs and devouring them with apparent delight. The largest V.p. rubidus recorded by Storr (1980) measured 50cm SVL (137cm TL). The largest specimen at Wanjarri measured 64cm SVL (155cm TL)and weighed over 5000g. Its swollen belly must have contained at least a kilo of festering meat. In comparison another specimen of 56cm SVL (135cm TL) weighed only 1750g. It was extremely thin and may have been attracted to the area from afar by the smell of decay. Bipedal ritual combat is said to occur between adults congregated around carrion (Bennett 1992). In this area the lizards are absent from areas of softer sand.

The only report of captive breeding in this species is by Haninger-Berlin (1994). A pair were allowed to remain inactive in the dark at 16-18oC for three months of the year, separated for a month  and then reunited, whereupon courtship,and mating occured within a month. A single clutch of up to 11 eggs is produced which hatch after 210-229 days at 28oC. At cooler temperatures they can take up to 356 days to develop. Hatchlings measure about 30cm TL and weigh around 27g. These animals require spacious enclosures with plenty of hiding places.

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Since 1999 the Butaan Project has been studying the rare, endangered, and unique fruit-eating monitor lizards of the Philippines.  Butaan is just one of several races of frugivorous monitor lizards in the Philippines ("Pandan Biawak"), all of which are of at least as great a conservation concern as the Komodo dragon, but receive virtually none of the attention. Pandan Biawak occur only in lowland dipterocarp forest. The first species (Butaan) was discovered in 1845 and not seen alive by a scientist until the late 1970s. The next species (Mabitang) was discovered in 2001. Other species remain undescribed, and some may have gone extinct without ever having been recognised.

 

 

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