What does it look like?
Eastern bearded dragons are grey-brown reptiles native to Australia, which can grow to 55cm long. The throat is covered with distinctive spiny scales which can be raised to form a black "beard". The head is large, relatively long and triangular in shape, and the inside of the mouth is usually a bright yellow colour. Bearded dragons have a low wide body shape, and long spiny scales along the lower sides of the body. The tail is almost the same length as the head and body. Bearded dragons are active during the day and can move with considerable speed. Juveniles are insectivorous and adults are omnivorous, eating mainly insects and some vegetation. The lifespan in the wild is unknown but they are known to live for more than 10 years in captivity.
In eastern Australia, they are common in open forests, particularly eucalypt forests, heathland and scrub and are also found in agricultural and urban areas. They prefer areas with trees (or fence posts) that they can climb to escape predators, sun-bake and survey the area. The main habitat areas generally have an annual rainfall of less than 381mm. They are able to withstand lower temperatures and higher humidity, making them more likely to be able to survive in the wild in some parts of New Zealand. Modelling indicates a moderate risk of establishing in the wild in parts of New Zealand.
Bearded dragons do not appear to have established invasive populations in other countries but have established self-sustaining populations in other parts of Australia. None are known to be in the wild in Northland, or elsewhere in New Zealand. Climatic suitability modelling suggests the northern part of the North Island and coastal areas of the Bay of Plenty, Hawkes Bay and the Wanganui-Manawatu areas could provide suitable conditions for eastern bearded dragons.
Why is it a problem?
When threatened, eastern bearded dragons typically "freeze" in position and then retreat to their preferred perch. They will flee at imminent threat, and in response to a perceived threat of attack will open their mouth to display the bright yellow colour inside, and extend the "beard".
In Australia, numbers are thought to be declining, but it is not considered to be threatened or at risk. It is a wide ranging species which also inhabits human-affected environments, with an opportunistic diet and is facing no major threats at this time. Road kill is recognised as a threat, as the dragons bask in the warmth of the road, but the risk has not been quantified. Other threats include hostile habitats and predation. Domestic pets such as cats and dogs, are known predators of bearded dragons.
Eastern bearded dragons mate in spring (September to December) in Australia, and females lay a clutch of approximately10-35 eggs about one month later. The eggs are laid in shallow holes dug into the soil in an open sunny spot, and incubate for 2-3 months, hatching in summer. Females may lay up to three clutches in one breeding season and first reproduce between 2-4 years old.
The population in Western Sydney underwent a population crash in 2004. High rates of testis deformity were observed in males, which is likely to have contributed to the population decline. A possible cause of the deformity was thought to be atmospheric pollution.
Initial modelling of temperature-dependent embryonic/egg development using degree-day modelling suggests that it would be difficult for eastern bearded dragons to successfully breed in current New Zealand climate conditions. In addition to soil temperature, soil moisture content is an important factor in egg development.