Thorny Devil

Throny dragon (devil) face

Photo: Thorny devil with horns and false head

The thorny devil is a spiny lizard with an upper body covered in sharp spines and a fake head on the back of its neck, which it uses as a decoy to evade predators. It also has two large horns on its head, adding to the illusion of a dragon or devil. The thorny devil is also known as the thorny dragon and thorny lizard. These names reflect this lizard's frightening appearance. But actually, it is a harmless ant-eater.

The thorny devil's scientific name is Moloch horridus. It is the only species of the genus Moloch.

(This lizard is sometimes misnamed as a mountain devil. This is incorrect. The Mountain devil is a shrub that grows in New South Wales at elevations of up to 1000m.)


Thorny Devil Description What Does a Thorny Dragon Look Like?

thorny devil

Photo: Thorny devil colours when warm

The thorny devil is about 15-20cm (6-8 in) in length from its nose to the tip of its tail, and weighs 28-88g (1-3 oz). The female is slightly larger than the male. The thorny devil's most distinguishing feature is the intimidating spikes on its upper body. These thorns offer it protection from predators. If attacked, it puffs up its body and stiffens its spikes, making itself more difficult to swallow. The thorny devil also has another trick up its sleeve. It has a pretend head! Located on the top of its neck, this fake head looks like a large knob with two spikes on it. When threatened, the lizard hides its real head between its front legs and offers this fake head as a decoy. It has two small eyes, each protected by a horny spike.

Photo: Thorny devil morning colour when it is cold

The thorny devil is a cold-blooded (ectotherm) lizard. It regulates its body temperature using external sources such as sunlight or a warm surface. It usually starts the day with a drab olive-brown colour, and as it warms up, the thorny devil acquires its normal yellow, red and black colours. Because the thorny devil is cold-blooded and needs to warm its body up, it is active only during the day.

The thorny devil has a life span of 15 to 20 years.


Thorny Devil Walking Thorny Devil's Unusual Walk

Thorny Devil Walking

Watch Video

The thorny devil has an unusual way of walking. It lifts its tail into a vertical position and oscillates back and forth as it moves. It is not understood why this animal does this. It has been suggested that this stop-start movement and the animal freezing in place as it walks may be to emulate a leaf. It looks somewhat like a leaf when viewed from above, making it more difficult for predatory birds to spot it.


Thorny Devil Habitat Where Does the Thorny Devil Live?

Photo: Thorny devil distribution map

The thorny devils live only in sandy or sandy loam soils in the spinifex grasslands, scrublands and deserts of the Australian Outback. They are found in Western Australia, the Northern Territory, south-western Queensland, and western South Australia. Thorny devils are semi-nomadic and not territorial. They do not have exclusive home ranges.

Thorny devils are most active around a temperature of 24°c and retire into underground borrows and remain inactive when the weather is extremely hot (January and February) or cold (June and July).


Thorny Devil Diet What Does A Thorny Devil Eat?

Thorny devils are obligate myrmecophages—they only eat black ants. A thorny devil may eat 600-3000 ants a day. They are ambush predators that find a suitable location where ants visit or pass through and then sit and wait to pick off their prey with their sticky tongues as they pass by. It has special shearing teeth for slicing through the relatively hard chitin bodies of its ant diet.

Their average feeding rate is three ants per minute. Their maximum consumption rate is a blistering one ant per second.

Living in the dry arid deserts, the thorny devil has evolved ingenious ways to quench its thirst. It uses its body as a condenser of moisture and its skin like a drinking straw to collect water from dew and transport it to its mouth. On cool mornings dew collects on its skin. This dew is channelled by capillary action to its mouth along grooves between its spines. This capillary action is so effective that water even defies gravity and travels up its legs. Capillary action also allows the thorny devil to absorb moisture from damp sand. Absorption through sand is the thorny devil's primary source of water intake.


Thorny Devil Reproduction & Life Cycle

Thorny devils mate once a year in the late winter through early summer (August to December). The courtship involves a lot of head bobbing and leg waving by the male. If she is receptive, he mounts her and deposits his sperm. The female usually digs a shallow burrow on a southern-facing sand ridge and deposits 3-10 eggs. She then covers up the burrow and abandons the site. Depending on the temperature of the soil, the eggs incubate for 90-132 days. The young hatchling's first meal is their own egg casing, which they eat before digging themselves out of the burrow.

Male and female thorny devils are the same size when they are born and grow at the same rate for the first year, after which the female outpaces the male in growth until they reach the age of 5 years.


Thorny Devil Predators & Threats Thorny Devil Self-defence

Photo: Thorny devil on a road

The thorny devil's sharp spines discourage attacks by predators. These spines also make it difficult for a predator to swallow this lizard. The thorny lizard also has a false head on its neck. When it feels threatened, it lowers its head between its front legs and then presents its false head to its attacker.

Even though thorny devils are well camouflaged and armoured, they fall prey to goannas and birds of prey. When threatened, they freeze, even in mid-step. They will also puff themselves up and tuck their head between their front legs, making themselves more difficult to attack and swallow.

Thorny devils are frequently killed by humans who destroy their habitats and accidentally run over them with motor vehicles as they bask on the surface of a warm road.


Thorny Devil Conservation Status Is the Thorny Devil Endangered?

The thorny devil population is believed to be unthreatened.

• Australian Animals — List of Native, Introduced, Endangered, Rainforest Fauna