What does it look like?
Eastern water dragons are a grey to brownish-grey colour above with patterns of black stripes along the ridge of the back as well as down the tail. They also have a dark stripe horizontally from the eye extending down the neck. The limbs are mostly black with spots and stripes of grey and the tail is patterned with grey and black stripes. They are coloured yellowish-brown underneath, with the chest and upper belly becoming bright red in mature males. Eastern water dragons are the largest species of exotic lizard available in the New Zealand pet trade and can grow to 80 to 90cm long.
Water dragons are completely insectivorous as juveniles, and as they grow they become omnivorous with vegetable matter gradually making up almost half of the diet. In the wild, water dragons have been observed ground feeding on insects such as ants as well as foraging amongst the branches of trees for insects like cicadas. They may also eat molluscs and crustaceans from freshwater, as well as algae and crabs in intertidal zones, and are strong swimmers. Hatchlings and young dragons may also be eaten by adult water dragons.
In their native range, eastern water dragons are found along the east coast of Australia from Cooktown in the north down to the New South Wales south coast. They have broad environmental tolerances and are found in a variety of habitats from tropical rainforest in the north of Australia to alpine streams in the south. Their key habitat preference is flowing water with ample tree cover and basking sites. Water dragons are also found in built-up urban areas as long as these conditions can be found and water quality is reasonable. They are often found in tree branches overhanging water, and will drop into the water when disturbed.
Modelling indicates a very high risk of establishing in the wild in parts of New Zealand.
Why is it a problem?
There is potential for water dragons to dive into the water when disturbed; they are strong swimmers and can remain submerged for up to 60 minutes. Large adult water dragons have very sharp claws and can deliver a serious bite. They are capable of thriving in urban environments.
Dogs and cats can cause injury and death to eastern water dragons, and predatory birds may prey on young hatchlings and small juveniles. They are often seen basking on roads and concrete in Australia and many are accidentally killed by vehicles.
Breeding occurs with the onset of warmer weather in spring. Males become sexually mature at about five years old (snout-vent length 210mm and weight 400g) and females from four years. Males are highly territorial during the breeding season. In their native range, females can lay up to three clutches per year. Sperm storage has not been documented in this species, but is known to occur in a closely related species which has the ability to store sperm for up to 580 days after mating. Eggs are laid in sandy soil in clutches of six to 18 eggs, and hatch within 60-120 days. Incubation length depends on temperature, with eggs incubated at warmer temperatures hatching earlier.