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A goanna is any one of several species of lizard of the genus Monitor lizard found in Australia and Southeast Asia.
Around 70 species of Varanus are known, 25 of which are found in Australia. This varied group of carnivorous ranges greatly in size and fills several .Ehmann, Harald. Encyclopedia of Australian Animals: Reptiles. (1992), p. 144. Angus&Robertson, Pymble, Australia. .
The goanna features prominently in Dreamtime and Australian folklore.
Being predatory lizards, goannas are often quite large with sharp teeth and claws. The largest is the perentie ( V. giganteus), which can grow over in length. Not all goannas are so large; pygmy goannas may be smaller than the arm of an adult human. The smallest of these, the short-tailed monitor ( V. brevicauda), reaches only in length. They survive on smaller prey, such as insects and mice.
Goannas combine predatory and scavenging behaviours. They prey on any animal they can catch that is small enough to eat whole. They have been blamed by farmers for the death of sheep, though most likely erroneously, as goannas are also eaters of carrion and are attracted to rotting meat.
Most goannas are dark-coloured, with greys, browns, blacks, and greens featuring prominently; however, white is also common. Many desert-dwelling species also feature yellow-red tones. Camouflage ranges from bands and stripes to splotches, speckles, and circles, and can change as the creature matures, with juveniles sometimes being brighter than adults.
Like most lizards, goannas lay eggs. Most lay eggs in a nest or burrow, but some species lay their eggs inside termite mounds. This offers protection and incubation; additionally, the termites may provide a meal for the young as they hatch. Unlike some other species of lizards, goannas do not have the ability to regrow limbs or tails.
The South African term for a monitor lizard is leguaan and this word is also from Spanish 'la iguana'.
Other goannas are adapted to swampy coastal environments, such as the mangrove goanna ( V. semiremex). Further still, Mertens' water monitor (water goanna – V. mertensi), found in lagoons and rivers across northern Australia, is streamlined for swimming, using its tail as a paddle. Most other goannas are good swimmers, but tend not to voluntarily venture into water.
Meals are often eaten whole, thus the size of their meals may depend on the size of the animals. Many of the small species feed mostly on insects, with some being small lizard experts. Many of the medium to large species feed on whatever prey they can catch. This includes eggs, fish ( V. mertensi), birds, snails, smaller lizards, snakes, marsupials, and other small mammals, such as rodents. The giant perentie has been observed killing a young kangaroo, and then biting out chunks of flesh like a dog.
All species are carrion eaters, so feed on the carcasses of dead animals, including livestock and other large creatures. The smell of rotting meat also attracts these lizards.
Goannas also rear up when threatened, either chased or cornered, and also inflate flaps of skin around their throats and emit harsh hissing noises.
Some goannas lose their initial fear of humans, especially when food is involved (or has been previously involved). The wildlife authority recommends not feeding animals while in their territory. An attack can cause serious injury in exceptional cases, but most authorities doubt that a goanna will direct an intentional attack at a human unless the human has attempted to attack it (or grasp at it) first. Indigenous Australians who hunt goannas for food consider the perentie to be a high-risk (but tasty) quarry.
Debate is growing as to whether goannas are venomous. The incessant bleeding caused by goanna bites had been thought to be the result of septicemia, but a 2005 study suggested monitor lizards (including goannas) are venomous and have oral toxin-producing glands.
The goanna's hefty tail can be dangerous when swung, much like a crocodile's tail; small children and dogs have been knocked down by such attacks. Often victims in goanna attacks are bystanders, watching the person antagonising the goanna. Alarmed goannas can mistake standing humans for trees and attempt to climb them to safety, which is painful and can be distressing for both human and goanna.Underhill D (1993) Australia's Dangerous Creatures, Reader's Digest, Sydney, New South Wales,
European settlers perpetuated several old wives' tales about goanna habits and abilities; some of these have persisted in modern folklore among campers and bushmen. This includes the above-mentioned exaggeration of goannas dragging off sheep from shepherds' flocks in the night. This might even be exaggerated into child-snatching, rivalling (attack ) as a tourist scarer, but probably more convincing due to the reptiles' carnivorous nature and fearsome appearance.
A common tale was that the bite of a goanna was infused with a powerful, incurable venom. Every year after the bite (or every seven years), the wound would flare up again. For many years, herpetologists generally believed goannas were nonvenomous, and lingering illness from their bites was due solely to infection and septicaemia as a result of their saliva being rife with bacterium from carrion and other food sources. However, in 2005, researchers at the University of Melbourne announced that oral venom glands had been found in both goannas and iguanas. Goanna venom rocks the reptile record , UniNews Vol. 14, No. 22 28 November - 12 December 2005, University of Melbourne, Retrieved 8 March 2006
Because the goanna regularly eats snakes (which may involve a fierce struggle), including venomous species, they are often said to be immune to snake venom. However, no evidence found suggests an actual venom immunity. Other stories say that the lizard eats a legendary plant, or drinks from a healing spring, which neutralises the venom. (This idea is immortalised in Banjo Paterson's humorous poem "Johnson's Antidote".)
Goanna fat or oil has been anecdotally imbued with mystical healing properties (possibly in connection with their supposed venom immunity). Aboriginal people traditionally used goanna oil as an important bush medicine, and it also became a common medicine among Caucasians shortly after British settlement in Australia. Said to be a cure-all, and possessing amazing powers of penetration (passing through metal as if it were not there), it was sold among early settlers like snake oil in the Old West of North America.
A goanna features as the heroic figure Mr Lizard in the Australian author May Gibbs’ children's books Snugglepot and Cuddlepie. A bronze statue of the goanna Mr Lizard has been placed outside the State Library of Victoria.
The villain in the Disney film The Rescuers Down Under, Percival C. McLeach, has a pet goanna named Joanna.
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