The Australian water dragon is an arboreal lizard native to eastern Australia. They have long powerful limbs and claws for climbing, a long muscular laterally-compressed tail for swimming, and prominent nuchal and vertebral crests. Males show bolder coloration and have larger heads than females. There are two subspecies: the Eastern water dragon and Intellagama Gippsland water dragon. Eastern water dragons are usually white, yellow and red on the throat and possess a dark band behind their eye; Gippsland water dragons lack this and instead have dark bands on either side of their throat, which is blotched with yellow, orange, or blue. Both subspecies are light greenish-grey in overall color with black bands running across their back, tail, and legs. Water dragons can slowly change skin color to aid their camouflage and their skin will shed during periods of growth.
Australian water dragons are found in eastern Australia from Victoria northwards to Queensland. There may be a small introduced population on the south-east coast of South Australia. They live near creeks, rivers, lakes and other water bodies that have basking sites such as overhanging branches or rocks in open or filtered sun. Australian water dragons are very common in the rainforest section of Brisbane Botanic Gardens, and Mount Coot-tha in Queensland.
Australian water dragons are social and aggregate in groups in areas of suitable habitat. These groups usually consist of several females, juveniles and a dominant male. Males are territorial, and in areas of higher population density, they exhibit displays of aggression toward other males including posturing, chasing and fighting. Australian water dragons can be active both during the night and day. They are often seen in the morning basking on riverbanks and rocks, resting in trees, swimming, and foraging for food. They are shy by nature but readily adapt to continual human presence in suburban parks and gardens. These lizards are fast runners and strong climbers. When faced with a potential predator, they seek cover in thick vegetation or drop from an overhanging branch into water. They are able to swim totally submerged, and rest on the bottom of shallow creeks or lakes for up to 90 minutes, to avoid detection. Water dragons living in cooler Australian climates brumate (hibernate) over winter. They brumate in burrows between boulders and logs in or near riverbanks. In order to communicate with each other Australian water dragons use a variety of dominant and submissive signals including arm-waving and head-bobbing. Fast arm-waving signals dominance, while slow arm-waving signals submission.
The diet of Australian water dragons depends on their age. Juveniles and yearlings tend to feed on small insects such as ants, spiders, crickets, and caterpillars. When they get bigger, so does their prey. An adult diet includes small rodents such as baby mice, although insects are still the most commonly consumed. Australian water dragons also consume fruits, berries, and flowers.
Little is known about the mating system in Australian water dragons depends. Their breeding season occurs during spring. Females excavate a burrow about 10-15 cm (3.9-5.9 in) deep and lay 6 to 18 eggs. The nest is usually in sandy or soft soil, in an area open to the sun. When the mother has laid the eggs, she backfills the chamber with soil and scatters loose debris over it. Australian water dragons exhibit temperature-dependent sex determination; the sex of the hatchlings is determined by the temperature of the nest site. Hatchlings are fully-developed and independent from birth. When the young are born they stay near the entrance of the burrow for some time before leaving home. When they finally leave the nest, they tend to group together away from the adult population.
There are no major threats to Australian water dragons depends at present. However, they are prey to birds, snakes, cats, dogs, and foxes. Nestlings and smaller juvenile water dragons are vulnerable to predation by kookaburras, currawongs, butcherbirds, and other carnivorous birds. They are also prone to becoming road kill due to the attraction of warm bitumen and concrete for basking.
According to IUCN, the Australian water dragon is locally common and widespread throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.