Boyd's Forest Dragon (Hypsilurus boydii or Gonocephalus boydii) is restricted to the rainforests of northern Queensland, Australia, from just north of Townsville to near Cooktown. It is found in both upland and lowland rainforest, and is often seen around Lake Eacham (Yidyam) and Lake Barrine, and can also be seen in parts of Malanda Falls Environmental Park and at Mossman Gorge.
It has very enlarged cheek scales, a prominent crest, and a yellow dewlap under its chin. Adults are sexually dimorphic, with males larger than females and having larger, blockier heads.
It spends the majority of its time perched on the trunks of trees, usually at around head height, although daily movements can exceed 100 metres. When approached, it will usually move around to the opposite side of the tree, keeping the trunk between it and its harasser. It doesn't bask, instead letting its body temperature fluctuate with air temperature. The one possible exception to this general rule is gravid females, which are often observed sitting beside roads and exhibit elevated body temperatures. Lizards commence activity at dawn and cease activity at dusk, remaining active even when it rains. Activity is highly seasonal, all but ceasing during the cooler months, when lizards move into the rainforest canopy.
Both males and females appear to be territorial, with males defending an area of around 1,000 square metres. Female territories are smaller, with male territories often containing the territories of more than one female.
Diet consists primarily of invertebrates, with earthworms making up a relatively high proportion. Small fruits and vertebrates are also occasionally consumed.
Reproduction is via eggs, with clutch sizes varying from one to six eggs. Females in lowland populations may lay more than one clutch in a season. The eggs are laid in shallow nests, often in rainforest clearings - both natural and man-made (the verges of roads are particularly popular). Sexual maturity is achieved in around one to two years in lowland populations but probably takes at least a year longer in upland populations.