There are 11 genera and about 70 species of dragons (Agamidae) in Australia. In the Canberra region, there are six genera and six species.
The adult Bearded and Eastern Water Dragon are easily identified. Also it is relatively easy to distinguish Grassland Earless Dragons from other dragons. The other three dragons: the Jacky, Nobby and Mountain Dragons are harder to distinguish from one another.
One way that helps in distinguishing between local dragons is to know the relative sizes of different species. A standard measurement in the description of reptiles is the snout-vent length (SVL) which is measured from the tip of the nose (snout) to the anus (vent), and excludes the tail. The SVL of the six species are Grassland Earless 55mm, Mountain 82mm, Nobbi 84, Jackie 120mm, Bearded 245mm, and Water 250mm.
Knowing the habitat and distribution may also be helpful in the field. Bearded Dragons are widespread in lower lying country in the Canberra region. Eastern Water Dragons are never far from a rocky-watery habitat. Grassland Earless Dragons are confined in native grasslands. Jacky Dragons are widespread. Mountain and Nobbi Dragons are habitat specialist. The former is found in very high altitudes and the later seems to prefer rocky escarpment areas along major rivers.
Subtle differences in back markings, colour, size, spines along tail, mouth colour, habitat and behaviour help to distinguish Jacky, Nobbi and Mountain Dragons from each other. Different authors point to subtle differences in back markings to distinguish species, but this is difficult diagnostic characteristic. Each species is grey in colour but the Mountain Dragon is a little more brownish. In the breeding season the male Mountain Dragon develops a distinctive reddish hue. The Mountain Dragon has distinctive spikes along the edge of its tail; the Jacky and Nobbi do not. Mountain Dragons burrow and partially bury themselves, possibly to regulate temperature; the Nobbi and Jacky do not. The Mountain Dragon is less likely to climb onto rocks in open areas, it tends to remain in leaf litter and rarely breaks from cover. The Jacky is known to climb shrubs and trees. The Jacky has a bright yellow tongue and mouth which it appears to use to frighten off predators and to assert dominance; the Mountain Dragon has a yellow tongue and blue mouth and the Nobbi has a pink tongue and mouth.
Young Bearded Dragons also look like Jacky, Mountain and Nobbi Dragons but may be distingushed by the presence of lateral (side) spines which are absent from from the other three species.