The thorny devil (Moloch horridus) lives exclusively in the arid and semi-arid interior of Australia, occupying sandy deserts, spinifex grasslands, and scrubland across much of the continent’s dry inland. You will not find this lizard anywhere else on Earth. Its range stretches across central and western Australia, from Western Australia through the Northern Territory and South Australia into parts of western Queensland, and its entire biology is built around surviving in some of the driest landscapes on the planet.
The Australian Outback and Beyond
The thorny devil’s range covers a broad swath of inland Australia, but it is not evenly distributed. The lizard is most commonly found in the sandy plains and dune systems of the western and central deserts, including the Great Victoria Desert, the Gibson Desert, the Great Sandy Desert, the Tanami Desert, and the sandy margins of the Simpson Desert. Populations also extend into the semi-arid mallee and mulga shrublands that fringe these core desert areas. The species is absent from Australia’s wetter coastal margins, tropical north, and the temperate southeast. It does not occur in Tasmania.
Within this enormous range, thorny devils favor particular types of ground. They strongly prefer sandy or sandy-loam soils and are rarely found on rocky substrates or heavy clay. This preference makes sense given that the lizard buries itself in sand for shelter, and it also forages more effectively on the open, flat ground between low shrubs and spinifex tussocks where ant trails are visible and accessible. If you drove through the red-sand country of central Australia and stopped to look carefully along ant trails near low scrub, that is where you would have the best chance of spotting one.
Why Only Dry Country
Thorny devils are not just tolerant of dry conditions; they are structurally committed to them. Their skin is covered in a network of tiny channels between overlapping scales that collect and transport water to the mouth through capillary action. This system allows them to harvest moisture from sources that would be useless to most animals: dew settling on their skin at dawn, moisture absorbed from damp sand they press their bellies against, or the thin film of water left on surfaces after light rain.1PubMed. Cutaneous water collection by a moisture-harvesting lizard, the thorny devil (Moloch horridus) Research using micro-CT scanning has shown that these channels are not simple grooves but are hierarchically structured, with large channels subdivided by tiny protrusions into smaller sub-capillaries. This design extends the distance water can travel across the skin by about 39% and reduces the volume of water needed to reach the mouth for a successful drink.2PubMed Central. Adsorption and movement of water by skin of the Australian thorny devil (Agamidae: Moloch horridus)
This water-harvesting system is a major reason the thorny devil can persist in habitats where standing water is absent for months at a time. But it also means the lizard is essentially locked into arid environments. Its slow metabolism, small body size, and specialized skin would offer little competitive advantage in wetter regions where other lizard species are faster, larger, or more aggressive. The thorny devil is a desert specialist, not a generalist that happens to tolerate drought.
What They Eat and How Habitat Shapes the Menu
Thorny devils are ant specialists. They eat almost nothing else. But the specific ants they eat depend on what is available in their immediate surroundings. Field observations have shown that thorny devils typically position themselves over or beside an ant trail, either on open sandy ground or at the base of low shrubs, and use their sticky tongues to pick off passing ants one at a time. In areas without shrub cover, the ants eaten are predominantly small Iridomyrmex species, a genus of fast-moving, trail-forming ants abundant across Australian deserts. In areas where currant bushes are present, thorny devils shift to feeding mainly on Crematogaster species instead.3ResearchGate. The role of diet in determining water, energy and salt intake in the thorny devil Moloch horridus (Lacertilia: Agamidae)
This dietary flexibility, choosing whichever small, abundant, trail-forming ant species is locally dominant, helps explain why the thorny devil can occupy such a wide range of arid habitat types. Sandy plains, spinifex grasslands, and mulga scrublands all support different ant communities, but all contain at least one species of small, colony-forming ant in sufficient numbers to sustain a slow, sit-and-wait predator. The lizard does not need a specific ant species. It needs an ant trail.
A single thorny devil can eat thousands of ants in one sitting. Estimates from field studies suggest they consume between 750 and several thousand ants per meal, which provides both energy and a meaningful fraction of their water intake, since ant bodies contain moisture. This reliance on ants is another reason their habitat must be open and relatively flat: they need clear sightlines to ant trails and enough ground surface to position themselves effectively.
How They Move Through Their Home Range
Despite living in vast open landscapes, thorny devils do not cover much ground. A biotelemetry study tracking three males and five females in the Great Victoria Desert found that individuals moved up to 200 to 300 meters in a day, but average daily distances were much shorter. Males averaged about 67 meters per day, roughly double the 32-meter average of females. Activity was considerably higher in early spring (September through early October) than in the late spring and early summer period of late October through November.4Academia.edu. Natural history of thorny devils Moloch horridus (Lacertilia: Agamidae) in the Great Victoria Desert
These modest daily movements reflect the thorny devil’s energy-conservation strategy. In a habitat where food arrives one ant at a time and water comes in microscopic quantities collected through the skin, burning calories on long treks would be counterproductive. Instead, the lizard spends much of its time stationary, either basking to warm up for foraging or sitting near an ant trail and feeding. The seasonal shift in activity makes thermal sense too: early spring mornings in the desert are cool enough that the lizard can bask and forage through much of the day, while by late October daytime temperatures climb past the range where the lizard can comfortably be active on exposed sand.
Seasonal Rhythms and Dormancy
Thorny devils are not active year-round. During the coldest months of the Australian winter (roughly June through August), they enter a period of dormancy, burying themselves shallowly in sand and remaining inactive. This is not true hibernation in the mammalian sense but more of a torpor, where metabolic rate drops and the animal simply waits out conditions that are too cold for effective foraging. Desert nights in central Australia can drop close to or below freezing in winter, and a cold-blooded animal the size of a human fist has no way to maintain body temperature in those conditions.
They emerge in spring and become most active during September and October, which coincides with warming temperatures and increasing ant activity. Breeding typically occurs in spring and early summer, with females laying clutches of eggs in burrows dug into sandy soil. The eggs incubate underground for several months, relying on the consistent warmth of the sand. This reproductive cycle further ties the species to loose, sandy substrates: the eggs need the insulating and draining properties of sand to survive. Heavy clay soils would retain too much moisture and not enough warmth.
The Thorns and Color Change
The thorny devil’s entire body is covered in conical spines of varying size, giving it one of the most striking silhouettes of any lizard. These spines serve multiple purposes in its desert habitat. They make the lizard extremely unpalatable to predators that swallow prey whole, which includes most Australian snakes. The lizard also has a pronounced “false head,” a rounded knob on the back of its neck. When threatened, it tucks its real head between its forelegs and presents this false head to the predator, a decoy that may redirect a strike away from the actual skull.
Less obvious but equally tied to its habitat is the thorny devil’s ability to change color. The lizard is typically a mottled combination of tan, brown, orange, and grey, matching the tones of the sandy ground it inhabits. But it can shift its coloring over the course of minutes, becoming darker when cold (to absorb more solar radiation) and lighter when warm (to reflect heat). This thermoregulatory color change is especially useful in the desert, where the difference between morning shade and midday sun can represent a temperature swing of 30°C or more. A lizard that can fine-tune its heat absorption without moving to shade or sun has a real survival edge in open habitat with sparse cover.
Where You Are Most Likely to See One
If you are visiting Australia and want to see a thorny devil in the wild, your best odds are in the red-sand country of central and western Australia. The areas around Alice Springs, Uluru, and the sandy plains of the Western Australian wheatbelt fringe are all within the species’ range. Timing matters: you want to be there in spring, ideally September or October, when the lizards are most active. Early morning is the best time of day, as the animals emerge to bask and then forage before the midday heat forces them into shelter.
They are not rare within their range, but they are slow-moving, well-camouflaged, and small (adults are typically about 20 centimeters from nose to tail tip and weigh around 40 grams). You are more likely to spot one if you walk slowly along sandy tracks and scan for movement near ant trails than if you drive and stop at random. Wildlife parks and reptile centers across Australia also keep thorny devils, and for many visitors these offer a more reliable encounter than searching the outback on foot.
Threats and Conservation Status
The thorny devil is currently listed as least concern by the IUCN, meaning it is not considered at immediate risk of population decline. Its range is enormous, its habitat is largely intact (much of inland Australia is too dry for agriculture or development), and it has no commercial value that would drive harvesting. Compared to many Australian reptiles, the thorny devil is in a relatively secure position.
That said, the species is not immune to threats. Feral cats and foxes, both introduced to Australia by European settlers, prey on small reptiles across the continent. Road mortality is another issue: thorny devils sometimes bask on warm asphalt in the early morning, and their slow reaction to approaching vehicles makes them vulnerable. Habitat fragmentation from mining, pastoral land clearing, and altered fire regimes can locally reduce ant populations, which directly affects food availability. And climate change introduces longer-term uncertainty. If core desert regions become hotter and drier beyond the species’ already extreme tolerances, or if shifting rainfall patterns alter ant community composition, the thorny devil’s specialized lifestyle could become a liability rather than an advantage.
No Close Relatives Nearby
Moloch horridus is the only species in its genus. It has no close living relatives in Australia or anywhere else. Its nearest relatives within the broader agamid lizard family are genetically distant, and the thorny devil sits on its own long evolutionary branch. This isolation makes it something of a one-off among Australian reptiles: a lineage that committed fully to ant-eating and desert-dwelling and never diversified into other niches or habitats.
The lizard that looks and behaves most like a thorny devil is the Texas horned lizard (Phrynosoma cornutum) from the deserts of the southern United States and Mexico. Both species are spiny, flattened, ant-eating desert dwellers with skin channels that transport water. But this resemblance is convergent evolution rather than shared ancestry. The two lineages are separated by well over 100 million years of independent evolution. Their similarities are a product of similar deserts imposing similar survival challenges, not of being closely related. It is one of the more striking examples of convergence in reptiles, and it underscores how powerfully arid environments shape the animals that live in them.