Reptiles
Thorny Devil
Moloch horridus · also called thorny dragon, mountain devil, moloch
The thorny devil is one of the most distinctive lizards on Earth — a small, slow, entirely spine-covered reptile of the Australian desert that eats only ants and drinks through its skin. Its ferocious looks are a bluff; it is a harmless, low-energy specialist superbly tuned to one of the driest places animals live.
Overview
Thorny devils inhabit the sandy and gravelly deserts and spinifex grasslands of central and western Australia, an environment of extreme heat, cold nights, and almost no standing water. They are diurnal but avoid the hottest hours, sheltering in shallow burrows or under bushes, and they are naturally thinly spread — a consequence of their slow metabolism and narrow diet.
Drinking with the skin
The thorny devil’s most remarkable trait is how it gets water. Its body is covered in a fine mesh of capillary channels running between the scales, all interconnected and all draining toward the mouth. Any contact with moisture — dew on the skin at dawn, damp sand flicked onto the back, a brief shower, morning fog — is wicked into this network and drawn to the corners of the mouth, where the lizard “chews” to swallow it. The system moves water against gravity, so a thorny devil standing on damp sand can pull moisture up its legs and along its back to drink. In a desert with no rivers or reliable rain, this passive collection can be the difference between life and death, and it is now studied by engineers interested in moving liquids without pumps.
Defence
Everything about the thorny devil discourages being eaten:
- Spines over the entire body, so there is no comfortable way for a bird or goanna to bite it.
- A false head — a spiny lump on the neck — that the lizard raises while hiding its real head beneath its body, so a strike hits the decoy.
- A rocking, halting walk that breaks up the visual cues predators use to detect movement.
- Cryptic, colour-shifting camouflage that matches the red or yellow desert sand.
Diet
The thorny devil is an ant specialist, feeding almost entirely on small black ants of a few genera. It sits by a trail or nest and picks off ants one by one with its tongue, consuming hundreds to thousands per meal. Because it targets tiny, low-value prey, it moves and metabolises slowly and cannot afford fast pursuit or long-distance travel.
Reproduction
Females dig a nesting burrow up to about 30 cm deep in sandy soil in late spring and lay a clutch of around 3 to 10 eggs, which hatch after three to four months. Hatchlings are miniature versions of the adults and begin eating ants immediately.
Status
The thorny devil is Least Concern and widespread across arid Australia. It is naturally uncommon everywhere it occurs, and localised threats include habitat degradation from grazing and altered fire regimes, road mortality (the lizards bask on warm roads and move too slowly to escape), predation by feral cats and foxes, and disruption of the specific ant populations it depends on.
Thorny Devil: common questions
How does a thorny devil drink without a water source?
Through its skin, by capillary action. The scales are separated by a network of microscopic, half-open channels that form a continuous system across the whole body, all leading toward the mouth. When any part of the lizard touches moisture — damp sand it shovels onto its back, dew condensing on its skin overnight, a puddle it stands in, rain — water is drawn into these grooves and pulled along them to the corners of the mouth, where jaw movements swallow it. The lizard can even collect water by pressing its belly into moist sand and letting the grooves wick it upward against gravity.
Why does the thorny devil have a "second head"?
On the back of its neck is a spiny, knob-like lump often called a false head. When threatened, the lizard tucks its real head down between its front legs, leaving the false head raised and presented to the predator. A bird or goanna that strikes at it bites a mouthful of hard spines and bone rather than the vulnerable real head, and the thorny devil's odd rocking gait and cryptic colour also make it a difficult target.
What does the thorny devil eat?
Small black ants, and very little else. It positions itself on an ant trail or beside a nest and flicks up individual ants with its sticky tongue, eating anywhere from hundreds to a few thousand in a sitting. This narrow diet means it needs specific ant species (mostly Iridomyrmex) to be present, which restricts where thorny devils can live and makes them slow-moving and low-energy by necessity.
Is the thorny devil dangerous?
Not at all. The spines are purely defensive and the lizard has no venom, is not aggressive, and is too small and slow to harm a person. Its fearsome scientific name — Moloch horridus, after a Canaanite deity associated with sacrifice — reflects its appearance, not its behaviour. Handled thorny devils are docile, though the spines are genuinely sharp.