For nearly as long, they've been mystifying scientists. Many theories for the circles' existence have been offered: termite eating patterns, carnivorous ants, plant-killing hydrocarbons and more.
Now a new study, utilizing aerial photos, rules out the possibility of termites as fairy circle creators. According to the researchers at the Helmholtz Centre for Environmental Research (UFZ) in Leipzig, Germany, "for the first time they have carried out a detailed analysis of the spatial distribution of these fairy circles."
The rings themselves aren't just geometrically impressive, but their relationship to each other also seems to follow a distinct spatial structure. The researchers say the pattern is too expansive to be the work of a typically erratic and frenzied species such as the termite -- let alone any insect.
"The occurrence of such patterning in nature is rather unusual," said study researcher Stephan Getzin. "There must be particularly strong regulating forces at work."
"There is, up to now, not one single piece of evidence demonstrating that social insects are capable of creating homogeneously distributed structures on such a large scale," Getzin added.
The German researchers say the most likely explanation is resource-competition, the quest for water on the edge of an arid ecosystem -- where grasslands transition to desert. As vegetation matures, and water resources are taxed, growth may thin out in a self-governing fashion, much the way young forests mature from dense brush to larger and more scattered trees.
"We consider this at present being the most convincing explanation," Getzin concluded.
The study was published this week in the journal Ecography.