Found by @xiaonixu0402. Uncommon prolonged and exposed view, the vole was apparently infected by unknown parasites. Similar to the description here, which suggests a possible infection of raccoon roundworms. The vole ran clockwise in circles almost endlessly with short pauses in between, likely when exhausted. Occasionally, it would almost flip itself, exposing its belly (photos 3 and 7). A quick search on iNat shows similar behavior has been documented several times in Bobolink Meadow, Jackson Park, the only documented place in Chicago currently. Here are the records: Sep-2014; Aug-2020; Jun-2022.