A goanna is any one of several species of lizard of the genus Varanus 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 reptiles ranges greatly in size and fills several ecological niches. The goanna features prominently in Aboriginal mythology 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 1.5 m (4.9 ft) 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 20 cm (8 in) 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.
Etymology The name goanna is derived from iguana. Early European bush settlers in Australia likened goannas to the South American lizards. Over time, the initial vowel sound was dropped. A similar explanation is used to link possums to the American opossum. The South African term for a monitor lizard is leguaan and this word is also from Spanish 'la iguana'.
Species
For a list of all monitor lizards of the genus, see Complete list of genus Varanus. The following are found in Australia. For the most part, in common names, "goanna" and "monitor" are interchangeable.
Perentie – V. giganteus Lace monitor – V. varius Sand goanna – V. gouldii (also Gould's goanna or ground goanna) Mertens' water monitor – V. mertensi Spiny-tailed monitor – V. acanthurus (also ridge-tailed monitor) Mangrove monitor – V. semiremex Black-headed monitor – V. tristis Short-tailed monitor – V. brevicauda Argus monitor – V. panoptes (also yellow-spotted monitor) Rosenberg's monitor – V. rosenbergi Spencer's goanna – V. spenceri Storr's monitor – V. storri Dampier Peninsula monitor – V. sparnus Mitchell's water monitor – V. mitchelli Kings' monitor – V. kingorum Southern Pilbara rock goanna – V. hamersleyensis Black-palmed rock monitor – V. glebopalma Kimberley rock monitor – V. glauerti Pygmy mulga monitor – V. gilleni Rusty desert monitor – V. eremius Stripe-tailed goanna – V. caudolineatus Pilbara monitor – V. bushi Black-spotted ridge-tailed monitor – V. baritji Emerald tree monitor – V. prasinus Canopy goanna – V. keithhornei
Habitats
Goannas are found throughout most of Australia, except for Tasmania, and manage to persist in a variety of environments. Most species are known to climb trees or outcrops; several primarily arboreal species are known. The lace monitor (V. varius) is probably the best-known among these, but is not the most common. The lace monitor is the second-largest of all goannas, reaching lengths up to 2 m (6.6 ft). Other more common tree goannas, such as the Timor tree monitor (V. timorensis) and mournful tree monitor (V. tristis,) do not grow to quite such lengths, typically a maximum of 61 cm, nose-to-tail. 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.
Diet The diets of goannas vary greatly depending on the species and the habitat. Prey can include all manner of small animals: insects, smaller lizards, snakes, mammals, birds, and eggs. 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 and humans
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