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Varanus giganteus Print E-mail


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

Varanus giganteus  Gray 1845

The perentie is the king of the Australian goannas. It is the largest lizard on the continent and one of the most beautiful animals in the world. It was once thought to be an uncommon creature but in recent years the number of sightings has greatly increased and the known range of the species has expanded. Despite their large size perenties are extremely shy and wary animals. Their pattern provides excellent camouflage and it is quite possible to walk within a metre or so of a large adult without ever being aware of its presence. Because of their ability to live undetected it is not clear whether perenties have expanded their range in the last few decades (see below) or whether they have succeeded in remaining unnoticed in many areas until recently. The perentie is found in arid areas of all mainland Australian states except Victoria and inhabits many islands off the western coast (Storr 1980). It is absent from the east coast and the tropical forests of the north, with northern and southern limits at about 18o and 30o longitude (Gow 1981a; Storr 1980; Houston 1978). They are said to be particularly common on Barrow Island off Western Australia (Smith 1976; King, et al 1989).

The maximum size of the perentie is probably not as great as many authors claim. King & Green (1993) provide a useful discussion of size in this species. Stirling (1912) suggested a maximum size of almost 230cm. The longest found on Barrow Island by King et al (1989) had a total length of 196cm (88cm SVL) and the heaviest weighed 11.7kg. Butler (1970) records a specimen of 17kg with a total length of 193cm from the same island. Stokes (1846) records that two specimens collected on Barrow Island in 1840 had total lengths of 213cm. Strimple (1988) suggested that one of these animals was the type specimen used by Gray, which has a total length of only 202cm (Mertens 1958).  Many perenties do not grow to such an enormous size, and the specimens on Barrow Island may grow larger than the mainland population (Case & Schwaner 1993). The limited data available suggests that females reach a smaller maximum size than males, rarely exceeding 140cm TL. Bredl (1987) records males of 180 and 190cm TL, and a female of 130cm TL. A male kept for 14 years in captivity had a total length of 135cm and weighed 2.9kg, whilst a female kept for seven years measured 116cm TL and weighed 1.55kg (Banks, pers.comm.). A specimen I saw in the Great Victoria desert measured 52cm SVL (123cm TL) and weighed 1.8kg when its stomach was empty. It appears that perenties approaching 200cm in length are the exception rather than the rule, and that in general few specimens grow larger than 150cm. If specimens of 240cm or more have ever existed, none seem to have survived to the present.

Perenties are associated with desert regions and particularly with rock outcrops. However they are also found on grasslands and shrublands devoid of exposed rock. Where caves and crevices are available the perenties will use them for shelter, otherwise they take refuge in burrows. Pianka (1994) suggests that the spread of rabbits through the interior of Australia may have enabled the perenties to occupy many areas that were previously unable to support them. The perenties certainly prey on mammals to a greater extent than any other Australian monitor lizard. Stirling (1912) and McPhee (1959) both record that they are able to kill kangaroos and dismember those that are too large to be swallowed whole with the powerful forelimbs and claws. Lizards probably account for most of their food, especially large and dwarf goannas including weaker members of the same species (Pianka 1994). They are also recorded as having eaten skinks, agamids, seagulls, orthopterans, centipedes and chilopods and are known to dig up the eggs and young of turtles from sandy beaches (Losos & Greene 1988; Green et al 1988, James, Losos & King 1992; Butler 1970). Much of the perenties' prey may be caught in open pursuit; they are reported to catch gulls by hiding under vehicles until the birds come close enough to allow them to be chased down before they can take to the air (Losos & Greene 1988; King et al 1989). Prey is usually killed by violent shaking. Horn & Visser (1988) suggest that perenties and sand goannas rarely occur in the same area, with sand goannas occupying open areas in contrast to the rock outcrops favoured by perenties. However a perentie we found on a flat spinifex plain in the Great Victoria Desert had swallowed a desert sand goanna almost the same length as itself and weighing about a quarter as much as its predator (Pianka 1994).

Stirling (1912) records that perenties will mistake stationary people or horses for trees and climb up them in their attempts to escape. One of the funniest sites I ever saw was a medium sized perentie climbing up a distinguished professor in the Great Victoria Desert of Western Australia. Far from "standing fearfully and awestruck" (Pianka 1994b) I was endeavouring to capture the moment for posterity when the lizard bit the professor severely and I had to abandon the camera. It is a testament to the professor's good nature that the perentie still roams the desert today, completely unaware of its highly improbable encounter at the hands of "The Pickler".



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Butaan start to visit fruiting trees before they are large enough to swallow the fruits. They make repeat journeys to trees, perhaps to reinforce memory of the position of the tree. If the youngster survives it may continue to use this tree for many decades. Fruiting trees like this are a vital resource for entire populations of butaan. Learn more >

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Varanus bitatawa

Varanus bitatawa is the third species of  monitor lizard to be recognised by science that belongs to the "Pandan Biawak" group,  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 (Varanus olivaceus or Butaan) was discovered in 1845 and not seen alive by a scientist until the late 1970s. The next species (Varanus mabitang or Mabitang) was discovered in 2001 and in 2010 Varanus bitatawa (Butikaw or Bitatawa) was described. Other species of frugivorous monitor lizards may remain undescribed, but many may have  gone extinct without ever having been recognised.




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