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https://en.wikipedia.org/wiki/Glacier_mice
"Glacier mice are colonies of mosses found on some glaciers and adjacent ecosystems. ... Glacier mice are notable for their movement across the ice, which appears to be non-random, taking the form of herd-like behavior. This movement is as yet unexplained,[1] and does not appear to be solely the product of wind or the direction of a slope. On average, they move about 2.5 cm (0.98 in) per day."