Zoo Friends - ZooNooz December 2003

Frilled Lizards are one of Australia's most popular and widely recognised reptile species. Their role as the mascot of the 2000 Paralympics, their image on the old two cent coin and a bizarre wave of "frillie-mania" which infected Japanese pop culture in the early 1980s, are all testaments to their iconic status.

Story by PAUL EVERY
Photographs Brian Chant and Kelly Winning
Illustration Ngaire Sales

Much of the lizard's notoriety can be attributed to its wonderfully ostentatious and distinctive frill. This frill is mostly used as a defensive bluff, making the lizard appear larger and more intimidating to potential predators. However, a male will also use his frill to display to rivals in defence of his territory.

The frill - a broad flap of skin extending around the base of the head - is supported by rods made of cartilage which in turn are connected to the muscles of the tongue and jaws, enabling the frill to be extended when the mouth is held open. When not displayed, the frill is kept demurely folded against the lizard's chest, neck and flanks.

The Australian distribution of the Frilled Lizard extends from the Kimberley region of Western Australia, across the Top End of the Northern Territory, through to Cape York Peninsula and eastern Queensland. However, as with numerous reptile species that we often consider as being distinctively Australian (such as Brown Snakes, Taipans, Carpet Pythons and Blue-tongued Lizards), "frillies" also have a range extending into Papua New Guinea and Irian Jaya.

They inhabit open forest and savannah woodland in areas characterised by distinct seasons of extended periods without rainfall alternating with months of monsoonal rains. During the dry season there is very little food or moisture, while during the wet there are abundant resources. Not surprisingly, this annual cycle of extreme and diverse environmental conditions influences much of the Frilled Lizard's behaviour throughout the year.

With the onset of the dry season, towards the end of April, frillies head to the tops of the larger trees where, in the relative safety of their refuge, they become less active. They reduce their body temperature and drop their metabolic rate dramatically to around one quarter of that in the wet season. This conserves energy as the food supplies dwindle, while still allowing enough body warmth to enable them to hunt, digest and avoid predators.

In the dry season they use an energy efficient sit-and-wait, ambush style of hunting, and their acute eyesight means they are highly attuned to detecting the movements of potential prey.

The limited supply of insects as the dry progresses reduces food consumption to half that of the wet. By September, most frillies are experiencing physiological stress from lack of water, but despite this their body weight does not fluctuate.

For maturing lizards, significant growth occurs for the first time since April.

The build-up to the wet in October and November heralds the new breeding season. Metabolic rate and body temperature again rise and, for males, it is a time to tenaciously defend their territories. The flamboyant frill displays frequently give way to athletic physical bouts, with the victor winning rights to the realm. Breeding season is taxing for the males and, after maintaining condition throughout the dry season, the battle-weary boys finally succumb, losing a significant proportion of their body weight.

The onset of the wet in December replenishes the larder with insects, food is abundant and access to water is unlimited. The lizards come down from the tree-tops and spend more time on the trunks and in saplings from where they pursue prey on the ground.

Unlike most lizards, which usually have uniform, undifferentiated teeth, frillies possess four prominent fangs. However, belying this impressive gape, they are almost exclusively insectivorous, using a slightly sticky, broad, fleshy tongue to pick up a wide variety of prey including termites, centipedes, cicadas, ants and locusts.

For maturing lizards, significant growth occurs for the first time since April. And for the adult females, the time has come to lay their eggs.

After excavating a burrow, a female will deposit a clutch of eight to 12 eggs, in the late afternoon. Another smaller clutch may be laid later in the season, utilising sperm stored in the female's body from the previous mating.

Eggs hatch in two to three months, giving those of the earlier clutch an advantage over their younger siblings - several more weeks of access to the wet season's bountiful insect harvest before the hardships of dry begin again.

Want to read more?

By joining as a Zoo Friends member we send you a full colour, glossy magazine each quarter as part of your membership package. Join now.

« Back to ZooNooz article listing