Artificial streetlights are causing thousands of woodlice to form large circular "death spirals" in northern Israel. The behavior was documented by researchers from The Hebrew University of Jerusalem. It marks the first known instance of such collective movement in these ground-dwelling isopods.
The discovery began when amateur naturalist Eviatar Itzkovich observed swirling groups of isopods on summer nights in the Golan Heights. PhD student Idan Sheizaf, supervised by Prof. Ariel Chipman, led the study on the species Armadillo sordidus. Experiments showed that white light beams create circular boundaries that draw the animals into rotating formations of more than 5,000 individuals.
Magnets and ultraviolet light had no effect, confirming that the geometry of streetlight illumination triggers the response. Most participants were female and many carried eggs, ruling out mating as the cause. The study also recorded the species for the first time in the Jezreel Valley.
Researchers noted that the spirals can expose the isopods to predators, such as centipedes, and waste energy needed for survival. Idan Sheizaf stated that the circular pools of light interact with the animals' instincts to produce this unintended phenomenon.
