Lizards of the rainforest

Skyrail Nature Diary: March 2011

Australia has the world's highest diversity of lizards, many of which can be found in the Wet Tropics Rainforests of Tropical North Queensland.

Lizards are intriguing creatures and are closely related to snakes. Some species are elongated with reduced or lacking limbs. The main differences to snakes is that lizards have external ears, eyelids and are usually able to lose their tails if necessary to escape a predator. Most lizards lay eggs but some give birth to live young. The eggs are generally leathery like snake eggs and there is no parental care.

Geckoes the scaly-footed lizards are closely related and unlike other lizards they have no eyelids and clean their eyes by licking them. Both are nocturnal and lay only two eggs. Geckoes have several leaf-like pads on their toes that allow them to climb almost any surface. The scaly-footed lizards resemble snakes and are often mistaken as one. Unlike snakes, they have two flaps where their hind legs used to be.

The largest of the geckoes are the Leaf-tailed Geckoes (Phyllurus spp.: Gekkonidae). These geckoes are moderately common in the rainforest of the Wet Tropics and are found nowhere else. Like their name suggests, their tails are swollen and often leaf shaped. It's believed that this has to do with camouflage or food storage. Being both nocturnal and blending in perfectly with their background, they are rarely spotted.

The most Australian of the lizards is the goanna. Most of the world's species are found in Australia, the largest being the Perentie (Varanus giganteus: Varanidae). Being the closest relatives to snakes, goannas never lose their tails and their tongues are cleft, like those of snakes.

The Lace Monitor (Varanus varius: Varanidae) is the most common goanna in the Wet Tropics. It's an excellent climber and leaves distinct diagonal scratch marks on the trees. It can grow up to 2m and is covered in transverse stripes. The Lace Monitor will eat anything it can fit into its mouth, including eggs. Unlike most goannas that rear up on their hind legs and hiss when threatened, Lace Monitors normally run for the nearest tree after a quick, initial, threatening hiss. Eggs are generally laid in termite nests after some excavation and the hole is quickly sealed by the termites. Females occasionally return to help their young escape from the mound.

Skinks comprise of the largest group of lizards in Australia. They have large noticeable scales, especially on top of their head. Limbs of skinks are often reduced and in some cases gone altogether. Skinks are often hard to tell apart from each other, making identification difficult.

The Pink-tongued Skink (Hemisphaeriodon gerrardii: Scincidae) is related to the better known Blue-tongued Skinks (Tiliqua spp.: Scincidae). Like the latter it's a ground dwelling species and feeds on insects and other small arthropods. The head is relatively broad and angular like the Blue-tongued Skink but the body is slimmer and the tail is prehensile, used for climbing low vegetation.

Dragons are an easily distinguished group of lizards with 60 species found in Australia. They have juxtaposed scales, often with greatly enlarged tubercles and spines.

In the rainforest the two most commonly encountered dragons are the Boyd's Forest Dragon (Hypsilurus boydii: Agamidae) and the Eastern Water Dragon (Physignathus lesueurii: Agamidae). Boyd's Forest Dragon is hard to spot as they usually climb trees and blend in with the bark, totally motionless. They have a spiny throat sac, large spines on the head and medium spines along the spine. Like the name suggests, the Eastern Water Dragon lives close to water and will dive in when frightened. They are slender with a long tail and have a distinct row of small spines along their back.