The Frilled Lizard: A Beautiful and Intimidating Reptile
The frilled lizard, or Chlamydosaurus kingii, also known as the frillneck lizard, frill-necked lizard, and frilled dragon, belongs to the Agamidae family. This lizard is native to northern Australia and southern New Guinea. Interestingly, it’s the sole member of the Chlamydosaurus genus. The lizard’s name comes from the large frill around its neck, which generally stays folded against its body.
Frilled lizards can grow up to 90 cm (35 inches) from head to tail and can weigh around 600 grams (1.3 pounds). Males tend to be larger and more robust than females. Their body colours vary, including shades of grey, brown, orangish-brown, or even black. The frills, on the other hand, can be quite colourful, featuring hues of red, orange, yellow, or white.
These lizards are mostly arboreal, meaning they spend a lot of time in trees. Their diet primarily consists of insects and other small invertebrates. They are more active during the wet season when they spend more time on the ground. During the dry season, they are less visible as they seek shade in the tree canopies. Breeding occurs in the late dry season and early wet season. The frill serves a dual purpose: it scares off predators and is used for display to other lizards. According to the International Union for Conservation of Nature, the species is not currently at risk.
Taxonomy
Back in 1825, a British zoologist named John Edward Gray introduced the frilled lizard to the world, giving it the scientific name Chlamydosaurus kingii. He based this on a specimen collected by botanist Allan Cunningham in Careening Bay, located off the north-western coast of Australia. This was during an expedition led by Captain Phillip Parker King aboard the HMS Mermaid.
The genus name, Chlamydosaurus, comes from the Ancient Greek word “chlamydo,” which means “cloaked” or “mantled,” and “saurus,” the Latin word for “lizard.” The specific name, kingii, is a nod to Captain King, Latinised for formality’s sake. Interestingly, this frilled lizard is the only species in its genus.
Belonging to the family Agamidae and the subfamily Amphibolurinae, the frilled lizard diverged from its closest living kin around 10 million years ago, as genetic evidence suggests. A 2017 study that analysed mitochondrial DNA across the species’ range identified three distinct lineages. These lineages are separated by the Ord River and the southeast corner of the Gulf of Carpentaria, also known as the Carpentarian Gap.
One lineage roams across Queensland and southern New Guinea, and it’s closely related to another lineage found from western Queensland to the Ord River. The ancestor of these two groups diverged from another lineage that inhabits the Kimberley region. It’s believed that frilled lizards made their way into southern New Guinea roughly 17,000 years ago during a glacial period when lower sea levels created a land bridge connecting the island to Cape York. The study supports the idea that C. kingii is a single species, with different populations forming what are known as “shallow allopatric clades.”
Anatomy of the Frill of Chlamydosaurus kingii
The frilled lizard, also known as Chlamydosaurus kingii, can grow up to about 90 centimetres (35 inches) in total length, with its head and body measuring around 27 centimetres (11 inches). These lizards can weigh as much as 600 grams (1.3 pounds). They have a notably large and broad head, a lengthy neck to support the frill, long legs, and a tail that makes up the majority of their length. The species exhibits sexual dimorphism, with males being larger than females and having proportionately bigger frills, heads, and jaws. The corners of their eyes are pointed, and their rounded nostrils face outward and downward. Most of their scales have a ridge running down the centre, and from the backbone to the sides, the scales alternate between small and large sizes.
The frilled lizard’s frill is a distinctive flap of skin extending from the head and neck, featuring several folded ridges. When fully extended, the frill forms a disc shape, reaching over four times the length of the lizard’s torso in diameter, roughly 30 centimetres (12 inches) across. When not in use, the frill wraps around the body like a cape over the neck and shoulders. The frill is symmetrical, with the right and left sides attaching at the bottom in a V-shape, and cartilage-like connective tissue known as Grey’s cartilage connecting the top ends to each side of the head near the ear openings. Rod-like hyoid bones support the frill, which is spread out by movements of these bones, the lower jaw, and Grey’s cartilage. This structure mainly serves as a threat display to predators and a means of communication between individuals. It can also act as camouflage when folded, although this is unlikely to have been a result of selection pressure. The frill might function like a directional microphone, allowing the lizard to better hear sounds coming from directly in front of it. There is no evidence for other proposed functions such as food storage, gliding, or temperature regulation.
Frilled lizards vary in colour, ranging from grey, brown, orangish-brown, to black dorsally, with a paler white or yellow underside. Males have a darker belly but a lighter chest. The underside and sides are sprinkled with dark brown markings that merge to create bands on the tail. The colours of the frills vary based on the lizard’s range: those west of the Ord River have red frills, those between the river and the Carpentarian Gap have orange frills, and those east of the gap have yellow to white frills. New Guinean frilled lizards have yellow frills. The more colourful frills often have white patches that may enhance their display. Colouration is mainly due to carotenoids and pteridine pigments; lizards with red and orange frills have more carotenoids, while those with yellow and white frills lack pteridines. Yellow colouration has been linked to higher levels of steroid hormones.
Distribution and Habitat
The frilled lizard, a fascinating creature found in the wilds of northern Australia and southern New Guinea, has a pretty extensive range. Over in Australia, these lizards can be spotted from the rugged Kimberley region in Western Australia, stretching all the way east through the Top End of the Northern Territory, and reaching as far as Queensland’s Cape York Peninsula. They even inhabit some of the nearby islands like Muralug, Badu, and Moa, and you can find them as far south as Brisbane!
When it comes to New Guinea, these lizards call the Trans-Fly ecosystem home, whether it’s on the Papua New Guinean or the Indonesian side of the island. They’re not picky about borders, it seems.
Frilled lizards have a preference for savannahs and sclerophyll woodlands, where they can enjoy the best of both worlds. They love hanging out in high-up areas with well-drained soil and a diverse mix of trees, especially the Eucalyptus kind. You won’t find them too often in the lower plains, which are usually dominated by Melaleuca and Pandanus trees—they’re just not fans of that sort of environment.
Another interesting tidbit: these lizards prefer spots with less ground vegetation. Why, you ask? Well, it makes it easier for them to spot their prey from above, giving them a better chance at a successful hunt. Clever little critters, aren’t they?
Behaviour and Ecology
The frilled lizard, a creature of daylight and tree-dwelling habits, spends most of its time high up among the branches, avoiding the ground except when absolutely necessary for feeding, socialising, or moving to a new tree. Males are more mobile, covering about 69 metres daily on average, compared to the 23 metres that females traverse in Kakadu National Park. In this area, males have a home range averaging 1.96 hectares during the dry season and 2.53 hectares in the wet season, while females stick to roughly 0.63 hectares and 0.68 hectares during the wet and dry seasons respectively. Male lizards mark their territories with impressive frill displays. These lizards can run on two legs, especially when hunting or evading predators, by leaning their heads back to align with the base of their tails for balance.
Activity levels spike during the wet season, with lizards choosing smaller trees and staying closer to the ground. In the dry season, they prefer larger trees and higher perches. They don’t go into torpidity during the dry spells but can significantly lower their energy consumption and metabolic rate when food and water are scarce. Their body temperatures can soar to about 40°C. They bask vertically on the main tree trunks in the morning and late afternoon, but in the dry season, they stop basking at lower body temperatures to conserve energy and water. When it gets too hot, they climb higher for shade. During wildfires, they seek refuge in large trees and termite mounds, and post-fire, they favour trees with more continuous canopies.
Frilled lizards primarily feast on insects and other invertebrates, rarely eating vertebrates. They favour termites, ants, and centipedes, with termites being crucial during the dry season and moth larvae during the wet. Interestingly, ant consumption dips after early dry season fires but rises after late-season fires. These lizards are ambush predators, waiting in trees for prey, then darting down on two legs before dropping to all fours to capture and consume their meal. Post-feeding, they retreat back up the tree.
Their predators include birds of prey, larger lizards, and snakes. When threatened, they flare their frills to appear larger, accompanied by gaping mouths, puffing, hissing, and tail lashes. If necessary, they flee and hide. They are also susceptible to gastrointestinal nematodes and have been known to succumb to cryptosporidiosis.
Breeding occurs during the late dry and early wet seasons. Competing males display open mouths and spread frills, sometimes leading to fights where they bite each other’s heads. Females dig shallow cavities for their eggs, laying multiple clutches per season with clutch sizes ranging from four to over twenty eggs. The incubation period lasts two to four months, with temperature influencing the sex ratio of hatchlings. Milder temperatures yield more males, while extreme temperatures produce more females. Hatchlings have smaller frills compared to adults. Growth happens mainly during the wet season when food is abundant, with males growing faster and dispersing further than females. Sexual maturity is reached within two years, with males living up to six years and females up to four.
Conservation
The International Union for Conservation of Nature (IUCN) classifies the frilled lizard as “least concern” due to its plentiful numbers and widespread habitat. However, it’s worth noting that in some specific regions, their population might be dwindling. The frilled lizard is quite the sought-after pet, which poses a risk to certain wild populations. Most of these pet lizards hail from Indonesia, since exporting them is prohibited in both Australia and Papua New Guinea.
Interestingly, the Indonesian government has declared the frilled lizard a protected species under Article 20 of the Environment and Forestry Ministerial Regulation concerning protected plants and animals. Breeding these lizards in captivity is no walk in the park, so many lizards labeled as captive-bred might actually be wild-caught.
Another threat to these lizards comes from feral cats. However, unlike other species, they don’t seem to be heavily impacted by the invasive cane toad.
Relationship with Humans
The frilled lizard, often hailed as one of Australia’s quintessential creatures alongside the kangaroo and koala, holds a special place in the continent’s wildlife tapestry. Archaeological findings hint at a time when indigenous peoples considered these lizards a part of their diet. Fast forward to the late 1800s, and you’d find William Saville-Kent, an adventurous soul, carting a live frilled lizard all the way to England, where it piqued the curiosity of biologists. There was even another one showcased in a Paris reptile exhibit, capturing the fascination of many as reptiles began to gain popularity as pets.
Thanks to its striking look and quirky behaviour, the frilled lizard has found its way into various media forms. Remember that intense scene in Steven Spielberg’s 1993 blockbuster, Jurassic Park? The dinosaur Dilophosaurus, with its dramatic neck frill flaring up during an attack, drew inspiration from our frilled friend. Its distinctive image also popped up in the 1994 LGBT-themed classic, The Adventures of Priscilla, Queen of the Desert. And let’s not forget, this iconic creature even graced some Australian coins, cementing its status as a national symbol.
