Zion and I walk each day (sometimes three times) in a not well known jewel of the City of Sarasota - Arlington Park. It's a lovely place, not immaculately groomed like many urban parks, but more like a bit of rural Florida in the middle of a City. We know many of the other "regulars" and their dogs but we encountered a stranger last week.
Stock photo', not mine
It was an American Mink, instantly recognisable by her/his bounding gait and swimming skills.
My best guess, based on his/her size is that she/he was a "farmed" mink - raised for the pelt (UGH) who broke loose.
Wikipedia tells me that minks are usually nocturnal and are solitary animals.