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The Biomimicry Manual: What Can a Thorny Devil Teach Us About Water Harvesting?
Image © Mark Roy
One of Australia’s more bizarre creatures is the thorny devil or dragon, also known as the moloch. The devil is named for the ancient god Moloch, a hideous demon smeared with the blood of child sacrifice, but in reality, she is five inches long and lives entirely on ants. The thorny devil is, of course, covered in fearsome thorns, presumably to warn off would-be predators, but the spiky scales also serve another ingenious function. They form an incredibly efficient water harvesting system. What can we learn about water management in our own increasingly parched world? Find out in today’s entry of The Biomimicry Manual!
Image © Johan Douma
The thorny devil is a master of camouflage and deception, changing color to blend in with her surroundings, and moving in agonizing slo-mo with a ritualistic freezing-and-jerk motion. She appears as a leaf in the wind, hiding expertly from birds, ants, and frustrated researchers. Once she is discovered, the thorny devil has another trick. Behind her head is a strange spiny knob. When threatened, she simply tucks her real head down between her forelegs, presenting a false one, and blows herself up with air like a puffer fish.
The spiky scales are not just for looks and prickles. They also collect moisture and funnel it, against gravity, and with no expenditure of energy, directly to the corners of her mouth. The water is not propelled by gravity, a pump, or suction. It is simply capillary action, the passive molecular attraction between the incredibly convoluted walls of the channels and the water coursing along them. The system effectively and efficiently sucks water from all over her body. She uses this superpower to the hilt, collecting nighttime dew, rubbing her belly on wet rocks, and kicking damp sand on her back. Like a walking sponge, the thorny devil gathers all the water she needs.
You may be thinking, doesn’t this lizard look a lot like our North American horned lizards from the desert Southwest? Definitely. Both are spiky and slow-moving, and both specialize in eating ants. Thorny devils eat virtually nothing else, as many as 3,000 in a single day. They flick a sticky tongue at them, one at a time, up to 45 times a minute. When unrelated organisms solve the same problem in a similar way, we call it ‘convergent evolution.’ Convergence is really interesting to us biomimics, because if a solution evolved twice, it must be a really good idea!
Image via WikiCommons
Here’s another good “idea.” A female thorny devil will spend days digging her nesting burrow. She goes exactly 9 inches down, and then takes a sudden right turn. She lays her eggs, climbs out, seals the tunnel, and carefully smooths the sand to leave no trace of her entombed treasure. Once born, the hatchlings munch on their own eggshells, gaining instant calories and nutrients before climbing out into a hostile world. Since other lizards simply cover their eggs with sand, leaving tricky pickings, the tunnel arrangement keeps the shells edible.
What can humans learn from this enterprising little beast? Could we borrow her spiky-scaled water-harvesting concept? Maybe collecting and distributing our precious water passively could help provide clean water to the 1 billion people who lack it. Or maybe it could reduce the energy needed to pump water to the tops of buildings, or suggest a variety of inexpensive technological solutions for managing water efficiently.
This thorny devil may be remind us of a hideous demon, but she may just hold a key to a real thorny devil of a human challenge.
An evolutionary biologist, writer, sustainability expert, and passionate biomimicry professional in the Biomimicry 3.8 BPro certification program, Dr. Tamsin Woolley-Barker blogs at BioInspired Ink and serves as Content Developer for the California Association of Museums‘ Green Museums Initiative. She is working on a book about organizational transformation inspired by nature.
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