Congratulations to “Maine Naturalist” and Stein for identifying not only that a Meadow Vole made the mystery tracks, but why they were circular! Thank you all for your comments, many of which were laughter-producing!
More NC readers have witnessed this phenomenon than I would have imagined – the tracks were made by a Meadow Vole that had neurological problems which could have been caused by a brain parasite, brain tumor, inner ear infection, or a stroke. While the exact nature of an affected vole’s neurological impairment cannot be confirmed without the vole in hand, it is highly likely that a common brain parasite, Toxoplasma gondii, is responsible for a vole running in circles.
The snow-covered corn field where these tracks were located was just down the road from a dairy farm, where it’s likely cats could be found. This is relevant because cats pass this particular parasite on to rodents (and birds) who eat the cats’ feces. The parasite goes to work on the brains of animals that have eaten cat feces, causing them to become disoriented (to the point where they lose their fear of cats). Cats then eat the fearless rodents and the cycle continues. When infected and disoriented, the rodents will often run in circles – hence, the unusual track pattern in the snow.
T. gondii can infect humans, too, through consumption of under-cooked foods, contaminated drinking water, and through contact with cat feces. This is why pregnant women are discouraged from tending kitty litter boxes, as the parasite can infect their unborn children.
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