I wonder how many of them actually leave, and how many just shift most of their activity to different hours, and often following a different food source for a period of time. For example, in a good acorn year (which this year should be), good luck patterning anything around here. A lot of the timber is oak dominant, and the deer just seem to wander randomly, finding fresh acorns along the way. A buck may still be there, but the patterns that seem so consistent are pretty much worthless for the rest of the fall. I think they just cut the time they are on their feet way down, saving their energy for the rut.