How a thorny devil collects and drinks water with its skin

Put six thorny devils in a lab with their feet in shallow water and something odd happens. Water creeps up their legs and over their bodies, and soon their mouths start to work. In one hour-long test described in a university news release, the lizards opened and closed their mouths almost 2,500 times and drank as much as 1.28 grams of water, about 3.3 percent of their body weight. Nobody had to hand them a cup.

The thorny devil (Moloch horridus) is a spiny, ant-eating lizard of central Australia, according to the Reptile Database. It has a body covered in large conical spines, and it has a problem: its mouth is adapted for eating small ants, so it cannot simply lap up a puddle. Its skin does the first half of the job instead, as a network of tiny channels that collect water and pass it toward the mouth.

This article explains how that skin works, how the water gets from the skin into the lizard, and what researchers have and have not shown about where the water comes from. We also flag where sources disagree, which is more often than you might expect for a lizard with so many photos online.

Meet the thorny devil

At Uluru, Parks Australia gives the animal’s name in the Pitjantjatjara and Yankunytjatjara languages as ngiyaṟi. It lives across central Australia, in the Northern Territory, Queensland, South Australia and Western Australia, according to the Reptile Database. The Animal Diversity Web and Pianka both place it on sandy soils: sand plains, sand ridges and mallee scrub, with spinifex grass and mulga acacia. It avoids rocky or hard ground.

The size row shows a typical problem. Pianka, a University of Texas herpetologist who has studied the animal in the field, gives 4 to 6 inches. PBS says about 8 inches. The Animal Diversity Web adds that body mass can shift by up to 30 percent within a few months, so even one lizard is not one size.

The skin as a network of straws

Overlapping scales form tiny channels across the thorny devil’s skin. A 2017 study in Royal Society Open Science by Philipp Comanns and colleagues describes them as hierarchical: large channels between the scales branch into smaller sub-channels. Water is drawn in by capillarity, the same effect that makes a paper towel creep into a spill. The large channels soak up water fast, and the sub-channels stretch the distance the water travels by about 39 percent and may reduce how much water the lizard needs to drink.

The team put a small droplet of 7 microliters on live lizards and timed it. The channels absorbed it in roughly one to two seconds, and the water kept spreading for about ten seconds, reaching a radius of about 9 millimeters. When it stopped, roughly half of the channel volume was filled. Those numbers come from six live lizards, so they show what the skin can do, not what every lizard does in every setting.

One finding sets it apart from a famous look-alike. The water spread evenly in all directions, with no preferred direction. The authors contrast this with the Texas horned lizard, whose skin moves water in one direction. Two spiny desert lizards, two different plumbing plans.

From skin to mouth

Moving water across the skin is only half the trip. The lizard still has to take it in. According to the 2017 paper, the water travels passively through the channels, while swallowing is active and uses jaw movements. A news release on a 2016 Journal of Experimental Biology study by Comanns and Philip Withers says the lizard sucks the water out of its skin channels, because it cannot lick.

That study’s numbers are striking. In the hour-long test, the six lizards, about 40 grams each, opened and closed their mouths almost 2,500 times. They drank as much as 1.28 grams in sips of about 0.7 microliters. The two numbers do not multiply out: 2,500 sips of 0.7 microliters would be about 1.75 grams, more than the 1.28-gram maximum, so not every mouth movement can have been a full sip. The release does not explain the gap. The skin channels could have held another 1.32 grams. Pianka’s description is plainer: grooves that lead to the corners of the mouth, a gulping motion, and up to about a gram of water gained in a rainstorm.

Where does the water come from?

Different sources point to different answers. Here is how they line up:

The dew rows disagree, and we cannot settle it. The lab used cooled lizards in a warm, humid room, which is not the same as dawn in the desert. The news release says Comanns never saw the lizards drink from sand either, so the sand conclusion is partly inferred. The honest summary: the skin clearly works with real water, and the question of which natural water sources matter most is still open.

Ants, a decoy head and a rocking walk

Water is only one trick. The diet is almost nothing but ants. PBS and Pianka estimate 600 to 2,500 in one meal, and the Animal Diversity Web puts it at about 750 a day. Parks Australia says it sits beside an ant trail and catches them with a sticky tongue. Ants are not very nutritious, which PBS gives as the reason for such large meals.

Defense is a theater production. A spiny knob on the neck acts as a false head. When threatened, the lizard tucks its real head between its forelegs and shows the knob, and it can puff up with air. Parks Australia says its rocking walk is thought to confuse birds of prey. Predators still get some, though: Pianka lists sand goannas, bustards and probably raptors, and says he found thorny devils in monitor lizard stomachs.

Color changes with temperature. The Animal Diversity Web says the skin is brown or olive in the morning and turns light yellow as the afternoon warms. Pianka describes pale yellow and red when warm and active, and a dark olive drab when cold or alarmed.

Common mistakes and myths about the thorny devil

Myth: it drinks like other lizards. It cannot lap water. Water moves through its skin and is taken in with jaw movements.

Unproven: dew is its main water supply. Some sources say it collects dew. The 2016 lab test found condensation did not fill the channels. Treat dew as unproven.

Mix-up: it is a “horned lizard.” Pianka describes the thorny devil and American horned lizards as a case of convergent evolution, where unrelated animals end up with similar solutions. He says most thorny devil spines, including the false head, are entirely boneless, while American horned lizards have bony cores inside their head spines.

Too simple: it is a small, one-size lizard. Sources give different lengths, and body mass can swing by a lot over a season.

Overstated: every desert reptile drinks this way. Our sources describe this skin trick for the thorny devil, with a comparison to the horned lizard, and we found no evidence about other species. For more lizards with odd body tricks, see the Common flying dragon, which glides on rib-supported wings, and the Gila monster. For a snake that has its own way of crossing loose sand, see the Sidewinder.

Conservation status

The thorny devil is listed as Least Concern on the IUCN Red List of Threatened Species. That is the category as distributed by GBIF, the Global Biodiversity Information Facility, and we checked it on November 9, 2026. Least Concern means the species was evaluated and does not meet the criteria for a threatened or near-threatened category.

The sources we opened name predators, but no modern threat and no population count. The Reptile Database calls the species not uncommon, pointing to more than 200 collected specimens, though we could not trace the citation behind that. The Animal Diversity Web says the species has not been evaluated by the IUCN, which differs from the category we read, so that note is probably out of date. That a threat is not named does not mean none exists. We have no confirmed population trend, because none of our sources states one.

Categories are reviewed and can change, and the copy GBIF distributes can trail the IUCN website by some months, which is why we print the date we checked. GBIF’s copy does not give the year of the IUCN assessment, so we do not state one.