The lizard's skin is not permeable; the water does not soak in. Instead the hexagonal scales are separated by semi-tubular grooves roughly a hundredth of a millimetre wide that interconnect across the whole body and converge on the corners of the mouth. Capillary forces pull liquid along them against gravity, and rhythmic opening and closing of the jaws acts as the pump that empties the channels into the buccal cavity.
Field observations show the animal pressing its belly onto moist sand and shuffling; laboratory work has quantified transport rates and shown that filling the system from damp substrate is slower and less complete than from standing water or rain. Condensed dew and rain running off the body are the more efficient sources.
The diet is comparably specialised: almost exclusively ants of a few genera, taken one at a time from trails, with counts often cited in the low thousands per feeding session. The claim sometimes made that a thorny devil can extract water from dry sand is wrong; the sand must be damp.