A desert lizard survives in arid conditions by harvesting and drinking water from puddles, and possibly even from moist sand.
The Australian thorny devil (Moloch horridus, pictured) has a micro-structured skin surface with capillary channels that collect and transport water to the animal's mouth. Philipp Comanns at RWTH Aachen University, Germany, and his colleagues found that this capillary system fills up completely when the animal stands in a puddle, allowing the lizard to drink the water. Conversely, when the lizard stands on moist sand, the capillary network fills to only about 59% of its capacity, and the animal is not able to drink this water. But tests of wet sand on skin replicas showed that moisture can be extracted from sand and pulled into the capillaries by gravity to fill them.
M. horridus has been observed in the wild shovelling wet sand onto its back, and the authors say this increases the contact area between skin and sand, boosting the volume of water it can collect and drink.