Australia is a land known for its unique wildlife, and among its large reptiles, a common question arises: are there iguanas, or are they goannas? While both are lizards, they belong to distinct families and originate from different parts of the world. The large lizards commonly encountered in Australia are indeed goannas, a type of monitor lizard, and not iguanas.
No Native Iguanas in Australia
Iguanas (family Iguanidae) are not native to Australia. Their natural habitat is primarily found across tropical regions of Mexico, Central America, South America, and the Caribbean. These herbivorous lizards, such as the green iguana, typically inhabit forest canopies, spending much of their lives in trees. Given their specific native range and ecological preferences, iguanas did not naturally establish populations in Australia.
Australia’s True Giants: Goannas
Australia is home to a diverse group of large lizards known as goannas, monitor lizards (Varanus genus), found throughout most of Australia, except Tasmania. They have adapted to various environments, including deserts, forests, and wetlands, with around 25 to 27 species making Australia a hotspot for monitor lizard diversity. The largest is the Perentie (Varanus giganteus), which can exceed 2 meters (6.6 feet) in length. Goannas are predatory, with diets varying by species, ranging from insects for smaller types to small mammals, birds, eggs, and carrion for larger ones. The term “goanna” is thought to be a corruption of “iguana,” stemming from early European settlers who mistakenly likened these Australian lizards to the iguanas they knew from the Americas.
Telling the Difference: Iguanas vs. Goannas
Distinguishing between iguanas and goannas involves observing several physical and behavioral traits. Iguanas have stockier bodies, prominent scales, a dorsal crest of spines along their back, and a noticeable dewlap (a flap of skin beneath their chin). Their diet is largely herbivorous, focusing on leaves, flowers, and fruits, especially as adults. They are also known for their arboreal lifestyle, frequently staying in trees.
In contrast, goannas possess more streamlined bodies with powerful legs and sharp claws, which are effective for digging and climbing. They have long, forked tongues, similar to snakes, which they use to detect scents in their environment. Goanna scales are small and granular, and they lack the prominent dewlap seen in many iguanas. While many goanna species are terrestrial, some are excellent climbers and swimmers, inhabiting a wide range of habitats. Their diet is primarily carnivorous, consisting of various small animals and carrion.
Introduced Species Considerations
Australia maintains strict biosecurity laws to protect its native ecosystems from introduced species. Iguanas are not native to Australia and are classified as prohibited invasive animals. This classification reflects their potential to cause significant ecological and economic damage if they establish wild populations. While rare instances of iguanas might occur due to illegal pet trade or accidental escapes, they are not established in the wild. The importation, keeping, breeding, or selling of iguanas without proper permits is illegal in Australia, with penalties applied to deter such activities. These prohibitions aim to prevent competition with native species, potential disease transmission, and disruption of the delicate ecological balance.