Nav: Home

Thorny devils tap damp sand to slake thirst

November 02, 2016

Scampering across the baking red Australian sand in search of an ant dinner, thorny devils look almost invincible in their coat of spikey armour; but their choice of diet may make survival more challenging in the harsh environment. Philipp Comanns from RWTH Aachen University, Germany, explains that the lizards' mouths are so well adapted to consuming ants that they are unable to lick water to drink. However, the resourceful animals have a remarkable alternative strategy to overcome the drinking problem: they have effectively turned the entire surface of their skin into a drinking straw.

Comanns describes how the reptile's skin is covered with microscopic channels that take up water by capillary action. The lizards then suck the water through the channels into their mouths: 'It is very cool seeing these lizards standing in a puddle and finally start to move their mouths as they drink', he says. However, it wasn't clear how thorny devils and other so-called 'rain harvesters' access water in one of the most arid environments in the world. They rarely encounter puddles and the dew that falls at sunrise only dampens the ground. Fascinated by the lizard's ability to extract water from the most parched locations, Comanns arranged to visit Philip Withers - who originally discovered the skin phenomenon - at the University of Western Australia, to find out more about how the mysterious creatures extract water from their desiccated surroundings. Together they discovered that the reptiles can drink by taking up water from damp sand and they publish their discovery in Journal of Experimental Biology at

Working with six thorny devils that had been caught in the bush by Graham Thompson, Comanns recalls that the animals were content to have their feet immersed in a puddle of room temperature water for an hour. Some even began opening and closing their mouths to drink within 10 s of being dipped into the water. Having weighed the lizards before they began drinking, an hour later (when they had drunk their fill and their skins were fully charged) and then an hour after that (when the skins had dried and any additional mass accounted for the water consumed), Comanns discovered that the 40 g reptiles opened and closed their mouths almost 2500 times during an hour-long drinking session and downed as much as 1.28 g of water (3.3% of body weight) in 0.7 μl sips. Meanwhile, the channels on the surface of the skin could hold an additional 1.32 g of water.

But Comanns was still none the wiser about which water sources that the animals depend on. Were they extracting water from damp sand, or could they gather enough dew on their chilly bodies from air warming in the early morning to slake their thirst? After allowing the lizards to stand in the damp sand and measuring how much water wicked up into the skin, Comanns found that even the wettest sand (22% water content) only saturated 59% of the capillaries and although Comanns assumes that this could be sufficient to satisfy the lizards, he never saw them drink. However, the animals like to cover their backs in damp sand and he suspects that this may allow them to extract more water. Also, when he cooled the lizards to 22°C and placed them in a warm humid room, the condensation that formed on the lizards' bodies was only sufficient to wet the surface of the skin and not enough to charge the water capillaries.

So, thorny devils can extract significant quantities of water from soggy sand but not enough from dew at sunrise and Comanns suggests that the lizards and other animals that resort to capillary action to get water shots should be rechristened moisture harvesters, 'Because it is not always about rain', he says.

REFERENCE: Comanns, P., Withers, P. C., Esser, F. J. and Baumgartner, W. (2016). Cutaneous water collection by a moisture-harvesting lizard, the thorny devil (Moloch horridus). J. Exp. Biol. 219, 3473-3479.

DOI: 10.1242/jeb.148791

This article is posted on this site to give advance access to other authorised media who may wish to report on this story. Full attribution is required, and if reporting online a link to is also required. The story posted here is COPYRIGHTED. Therefore advance permission is required before any and every reproduction of each article in full. PLEASE CONTACT

The Company of Biologists

Related Body Weight Articles:

Short-term study suggests vegan diet can boost gut microbes related to body weight, body composition and blood sugar control
New research presented at this year's Annual Meeting of the European Association for the Study of Diabetes (EASD) in Barcelona, Spain (Sept.
Increased body weight in adolescent boys linked with heart attack before 65
A study in nearly 1.7 million 18-year-old boys has found that higher body mass index (BMI) is linked with greater risk of a heart attack before 65 years of age.
Substantial increase in body weight since 1960s due to interplay between genes and environment
People with a genetic predisposition to obesity are not only at greater risk of excess weight, their genes interact with an increasingly 'obesogenic' environment, resulting in higher body mass index (BMI) in recent decades, finds a study from Norway published by The BMJ today.
Excess weight and body fat cause cardiovascular disease
In the first Mendelian randomization study to look at this, researchers have found evidence that excess weight and body fat cause a range of heart and blood vessel diseases (rather than just being associated with it).
New brain mechanisms regulating body weight
Researchers at University of Gothenburg, Sweden, clarify the link between the molecule interleukine-6 (IL-6) in the brain and obesity.
Excess body weight before 50 is associated with higher risk of dying from pancreatic cancer
Excess weight before age 50 may be more strongly associated with pancreatic cancer mortality risk than excess weight at older ages, according to results of a study presented at the AACR Annual Meeting 2019, March 29-April 3.
Personality type could shape attitudes toward body weight of others, researchers say
Researchers found that personality traits have significant bearing on a person's attitudes toward obesity, their implicit theories of weight and their willingness to engage in derisive fat talk or weight discrimination.
Proportion of cancers associated with excess body weight varies considerably by state
A new study finds an at least 1.5-fold difference in the share of cancers related to obesity between states with the highest and lowest proportions.
Excess body weight responsible for nearly 4 percent of cancers worldwide
Excess body weight accounted for approximately 3.9 percent of all cancers worldwide in 2012, a figure that is expected to rise in the coming decades given current trends.
The body weight bias in sales
Findings from a new study suggest that sales employees are more likely to recommend round products for customers that are overweight or obese, but there is no evidence that these customers prefer round products.
More Body Weight News and Body Weight Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.