Photo: Barking gecko at Jarowair sanctuary - Brendon and Judi Gray

This article featured in Wildlife Lands Issue 17

If you ask the average member of the public about geckos, chances are it will be the common house gecko (Hemidactylus frenatus) that springs to their mind – arguably Australia's most successful invasive reptile and our only introduced gecko species. It is unfortunate that more attention isn't given to the 140-odd currently recognised native gecko species, their diversity – from bold patterns to spiny tails to cryptic camouflage – being nothing short of incredible.

One noteworthy variety is the barking gecko (Underwoodisaurus milii), which is known to inhabit dozens of Wildlife Land Trust sanctuaries (including Jarowair in Queensland, pictured above). Named after their distinctive call, this gecko produces a surprising, guttural bark defensively when threatened or annoyed, as well as when mating. Varying in size, the average adult barking gecko weighs around 20-25 grams and has a body length of approximately 10-12 centimetres.

Distinguished from other gecko species in part by their darker purple-brown colour, barking geckos are covered in small raised, yellow spots called tubercles which are organised in bands along their heads, bodies and tails. They are also referred to as thick-tailed geckos due to their thick, broad tails which taper to a pointed tip. As is the case with many other lizards, barking geckos can drop their tails as an added defence mechanism. They are also known to shed their skin every couple of weeks.

Unlike many other Australian gecko species which are equipped with expanded toe pads for extra grip and the ability to navigate vertical surfaces, the feet of barking geckos are narrower with long slender digits, having adapted to spending the majority of their time on the ground. These terrestrial geckos are nocturnal feeders and their diet mainly consists of insects, spiders and other small invertebrates. During reproduction female barking geckos lay a clutch of two parchment-shelled eggs following a gestation period of about 30 days, which take approximately twice as long again to hatch. The self-sufficient young are thought to have a lifespan of several years in the wild and up to 15 years in captivity.

Barking geckos have a rather wide distribution across southern Australia and can be found in every state and territory except for Tasmania. They tend to live in wet coastal heathland, wet sclerophyll forest, dry woodlands and arid scrubland as these habitats provide ample shelter in rock crevices and under loose bark and leaves. Studies show these geckos actively aggregate and while there are many anecdotal explanations for this tendency, it is not yet fully known why they do so.

In terms of taxonomy, barking geckos have had a tumultuous time being reclassified over 20 times since they were first discovered in 1823. Over the last two decades its identity in the scientific world has alternated between its current name Underwoodisaurus milii and Nephrurus milii four times.