Desert Locomotion: Hand-Springing Spider Excites Bionics Experts

By Caroline Winter in Berlin

Forget about crawling. A spider discovered in the Sahara Desert moves by doing a series of hand springs across the sand -- and travels surprisingly fast. Bionics experts think the method could be used for future Mars explorer vehicles.

The white spider, which is slightly smaller than a man's palm, takes a running start before hurtling itself forward into a series of front handsprings. Gaining momentum, it quickly reaches a speed of up to two meters (6.5 feet) per second on even ground. It looks like a jet-propelled tumbleweed flying across the desert sand.

Professor Ingo Rechenberg first came across the nocturnal spider when it rolled through the beam of his flashlight on a night walk through the Sahara Desert. "I was hoping to find something special, but I wasn't expecting anything like this!" says Rechenberg, 75, who enthusiastically recalls how the fast-paced spider whizzed passed him.

Rechenberg heads the Department of Bionics and Evolution Techniques at Berlin's Technical University, where he presides over an enormous laboratory that spans several stories and is packed with colorful experimental equipment, chalkboards scrawled full of sketches and equations and glass tanks containing reptiles that swim through sand and other species of interest. The department's goal is to glean ideas from nature and apply them to engineering problems. Rechenberg hopes that his discovery will someday inspire an improved Mars explorer vehicle that can both roll and crawl.

The ground floor of the building contains two enormous red wind simulators, sample textiles for desert water pumps based on plant capillary systems, tiny flying devices, numerous airplane wing models and several black and white photographs of birds in flight. There are also two white vans, which Rechenberg has used for desert research over the past 25 years.

"I know my way around that part of the Sahara better than Berlin," the scientist claims, noting that he has even adapted to 45 degree Celsius (113 degree Fahrenheit) temperatures and befriended several nomad families, who have nicknamed him "Monsieur Sandfish" after one of his research specimens. Rechenberg developed a personal relationship with the Saharan natives because he often relies on their expertise to find and collect unusual specimens. Yet when he showed them his rolling spider, they were as stunned as he had been.

Rechenberg suspects that his spider remained in obscurity because it travels only at night, then hides in a web under the sand when the sun comes up. He discovered it after implementing a new research routine. Surrounded by nothing but sand and sky for six weeks straight, he followed a rigorous daily regimen: after rising at 3 a.m., he set out into the desert darkness with a high-powered flashlight and wandered until the sun rose and he could see enough to find his way back. It was on one such nocturnal sojourn that he spotted the rolling spider.

There are two other types of arachnids that are known to roll; a plump spider with stubby legs from the deserts of Namibia and the hairy wolf spider from Florida. Both like to climb up sand dunes, tuck in their legs, and passively tumble down in gravity-assisted flight. Still, they move nothing like Rechenberg's more athletic, long-legged specimen, which takes a running start in order to gather speed for its flips. Even when slowed on film to half-speed, it is difficult to follow the white spider's windmill motion. The tracks it leaves behind show that three of eight legs are always planted, probably to maintain stability.

None of these three spiders are specifically designed to roll. In fact, any spiders could theoretically travel via tumbling or handspring if they so desired, according to spider expert Dr. Peter Jäger of the Frankfurt-based Senckenberg Research Institute. The originality of these two spiders can be attributed to their environment, says Rechenberg, who prefers studying animals that exist in extreme climates that often necessitate novel means of locomotion and energy conservation.

"Rolling is more useful in the desert because of the smooth, flat terrain," says Rechenberg. Most animals, he notes, would not benefit from wheels, since they have to be able to climb and deal with challenging and diverse terrain. "This spider has the advantage that it can do both. It rolls on even ground and, when faced with more complicated, rougher terrain, it can go back to crawling and climbing."

Jäger doesn't think Rechenberg's spider rolls in order to save energy, but as a means of defense. He noted that the running start takes energy and that too much rolling can kill it. Indeed, that was how Rechenberg's first rolling spider met its unfortunate end: Trying to capture its motion on film, the scientist spurred it to roll over and over again as sun rose. After several consecutive rolls, the spider laid down and died.

Rechenberg found two more such rolling spiders over the next few weeks and brought them back to Germany in order to prove his discovery. One male specimen currently inhabits a jar of alcohol in the offices of spider expert Jäger. The other -- dubbed Ariadne after the Greek goddess who gave her lover a red ball of thread to help him escape a Minotaur's labyrinth -- lives in Rechenberg's home along with 15 sandfish. If Adriadne is female, biologists may be able to conclude whether or not Rechenberg's spider is in fact a new species. If it is, it will be called Cebrennus rechnebergi.

Rechenberg plans to return to the Sahara in order to collect more of these odd arachnids next summer. Once he has enough specimens to work with, the next step will be perfecting a robot that mimics their desert locomotion style. If all goes well, that robot will then find its way to Mars.

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