I've seen the exact same behavior with white-tail deer. All summer, they will be in the field and gardens back of the house, morning, noon and night, but as soon as November rolls around, they ghost during daylight hours, and retreat into the thickest softwood or hardwood whips or swamp, where the hunters can't push them out. Until you get to the first snow, and can actually stay on their tail and track them down, it's hard hunting.