(Source: Dr Ellen K. Rudolph/)
Like Goldilocks tasting porridge, female frilled-neck lizards test dozens of nesting sites, digging holes and probing with their snouts for temperature conditions that are just right.
The temperature at which the eggs are incubated determines the sex of the baby frilled-neck lizard, but it does much more than that.
“Temperature affects things like the size of the hatchling, shape, behaviour, their running speed, a whole range of things,” explains Professor Rick Shine of Sydney University.
Once the eggs are buried, maternal instincts run out and the shallow nest is abandoned to incubate for 8-12 weeks. When they hatch, the youngsters are Territory-tough and fend for themselves from birth.
Like many of the roughly 70 members of the Dragon family (Agamidae) around Australia, frilled-necks are great communicators. Intimate conversations with other ‘frillies’ include actions such as head-bobbing and waving fore-legs about.
In contrast, enemies are presented with a spectacular bluff. The iconic frill is flashed up, multiplying the lizard’s apparent size tenfold; the strong rough tail thrashes about; the lizard’s fearsome bright pink or yellow-lined mouth gapes and hisses, and it lunges forward. Then, while the startled foe decides whether to flee or fight, the lizard turns and skedaddles for the nearest tree.
Right from an early age, frilled-neck lizards use their frill. “I’ve seen them flapping the frills with just the head sticking out of the egg”, reports Keith Christian of Charles Darwin Uni. “Day-old youngsters instinctively display to birds, snakes and other perceived threats, like us humans.”
Adult males will also engage in ‘sabre-rattling’ from the safe heights of their tree, advertising their claim to their 2 hectare territory by loudly lashing their tail against the trunk whilst puffing their large dinnerplate-sized frill in and out. If this intimidation fails, fights ensue. Amazingly, many losers survive despite suffering broken jaws.
When: Matting occurs around September, with the female laying in November. The hatchlings start appearing in early February.
Where: Northern Australia & southern New Guinea mainly in savanna woodlands, in higher and better-drained areas.
Other info: Name: Chlamydosaurus kingii (=King’s cloaked lizard)
Size: Adult ~70-95cm overall, tails up to 60cm long. Hatchlings ~5-6cm
Weight: up to 500gm
Colour: Usually mottled grey, brown, or reddish-brown. Frill can have bright orange and red scales. Young are darker.
Diet: Mainly arthropods (insects (eg. termites, grasshoppers, caterpillars, beetles) and arachnids (centipedes, spiders, etc); rarely small vertebrates.
Predators: birds of prey- hawks, eagles and owls; pythons, large snakes and goannas; dingoes and quolls; humans.
Courtship and mating: From early wet season (mid-October) in NT
Reproduction: Females can lay up to 3 clutches of 8-20 eggs, each weighing 3-5 grams, in a season.
Lifespan: Of lizards surviving to adulthood, probably over 6 years & up to 20 years.
Conservation Status: Secure
The Gunwinku people of NW Arnhem Land, who live around the township of Gunbalanja (formerly Oenpelli) tell this story about Gurndamen, the frilled-neck lizard. Back in the Dreamtime, there was a young man who crept up to snoop on some old men who were telling secret sacred stories. He hid behind some bushes so he could listen to them. Somebody saw him and he was hauled up before the old men. To symbolise the law he had broken, they gave him one huge ear. That ear became the frill of Gurndamen, the frilled-neck lizard. Ever since then he’s hidden away in shame, living high up in the treetops during the Dry season.
Funny AND special!
When threatened by predators or fire, frilled-neck lizard have been known to jump 20m down from a branch. Once on the ground they can run on their back legs – or walk, if a more leisurely pace is appropriate. The end result is quite comical, says Rick Shine. “It’s hard not to laugh watching these funny little lizards wandering around on their back legs out in the scrub.”
It also appears to be unique, according to Shine. “I don’t know of any other lizard around the world that walks around on its back legs. It really is a substantial trick to pull off in evolutionary terms,” he says.
Frilled-neck lizards are ‘sit and wait’ predators, which is an approach that helps them conserve energy. They chose trees where they can survey the area for food, before racing down to nab it! The type of tree you’ll find them in varies with the season, according to Tony Griffiths from Darwin Charles University.
“They tend to choose significantly, larger trees in the Dry season, where they’re more hidden and further away from danger while in a semi-dormant state,” he says.
But when the build-up to the Wet season starts the lizards choose much smaller trees.
“More animals can see them displaying” says Griffiths, “and they’ve got a better view of the world.”
Griffiths has been studying the positive effects of fire on frilled-neck lizard food sources. It’s much harder for the lizards to find food in areas that haven’t been burnt for a long time, because of the build-up of leaf litter.
“I watched one lizard walk 2km and cross a road” he says, “As soon as he got to the other side where it had been burnt, he set up shop 20m from the road. There he had nice open ground. He could climb a tree and look down on the ashes. “
In this case we know exactly why the lizard crossed the road!