A living sponge
The thorny devil (Moloch horridus) is adapted for survival in the arid scrublands and deserts of central Australia. Growing up to 21 cm long, this lizard's most obvious feature is its intimidating covering of conical spines. These are for defense and they are part of a complex water-gathering system that allows the animal to thrive where water is scarce. The lizard's skin is covered in a network of microscopic, half-open channels and grooves that lie between its scales. The network acts like a sponge or blotting paper, drawing in any available moisture from the environment.
This water collection is a passive process driven by physics. When the lizard's skin comes into contact with water—from rain, dew-covered vegetation, or even just damp sand—capillary action wicks the fluid into the network of grooves. These channels are interconnected across the entire body and lead to the corners of the lizard's mouth. Water can travel against gravity, moving up the legs and across the torso to be drunk. The total water volume that the skin's capillary system can hold is about 3.19% of the lizard's body mass. Once the water reaches the mouth, the thorny devil makes small jaw movements to actively drink the collected fluid, consuming about 0.7 microliters per movement.
Adapted for a harsh life
The thorny devil's water-harvesting skin is one of its many adaptations to desert life. Its jaw and tongue are specifically shaped for its diet, which consists almost exclusively of ants. It can consume thousands of ants in a single day, often eating at a rate of 45 ants per minute. This specialized diet makes it difficult for the lizard to drink water directly from a source, making its unique skin even more important.
For defense, the lizard relies on its spiky armor, which makes it difficult to swallow. It employs camouflage, changing its color from pale yellows in warm weather to darker reddish-browns to match the soil. When threatened, a thorny devil will tuck its real head between its front legs and present a large, spiny knob on the back of its neck. This "false head" is made of soft tissue and is a decoy for predators like goannas and birds of prey. The lizard also has a distinctive slow, jerky gait that involves rocking back and forth as it walks, possibly to mimic a wind-blown piece of vegetation and confuse predators.