In the most arid places on the planet, hydration is hard to come by and easy to lose. Every moist breath exhaled, every bead of sweat that drips off, and every emptied bladderful of urine means wasted wetness and a greater risk of death by dehydration. Yet some animals manage to survive in these places. They get by on almost no water at all, thanks to clever adaptations that make them super savers and hydration scavengers.
In the Mojave and Sonoran deserts, several tortoise species survive off their urine. During times of plenty, their bladders swell to hold around 16 ounces of liquid gold—impressive for a reptile that’s only about 12 inches long. The tortoise can later reabsorb water from its urine to endure
a year or longer without a drink.
The kangaroo rat never has to drink water—it just gets it from the seeds it eats. To survive in the dry climes of the American West, its kidneys generate super-concentrated urine, and it doesn’t pant or sweat. Some species can even lower their metabolic rates so they lose less moisture through breathing.
The spikes of Australia’s thorny devil do more than ward off predators. The lizard’s absorbent skin and spines suck up dew from cool night air, rain, puddles, and any other moisture it can get its dry little claws on. Thin grooves in its skin help trap the water, then route it to the lizard’s mouth for a tipple.
During hot, dry periods, this Australian frog secretes a waterproof mucus cocoon that prevents moisture from escaping its body. Meanwhile, the frog hibernates underground, waiting for another rainy season. It can survive for two years or more on the liquid stored in its bladder.
Camels don’t actually store water in their humps, so they have to conserve it. At night, after the chilly Saharan air cools the camel’s nasal cavity, mist in its breath condenses inside its nose, where it gets reabsorbed. The camel’s extra-twisty nasal passages save up to 60 percent of the moisture it would have lost during exhalation.
Sand gazelles in the sweltering Arabian Desert have evolved the strange ability to shrink their oxygen- demanding organs when dry spells hit. Downsizing their hearts and livers by 20 and 45 percent, respectively, allows them to breathe less. Taking fewer breaths means less water lost to respiratory evaporation.
This article was originally published in the March/April 2017 issue of Popular Science, under the title “Moisture Misers.”