It varies a bit year to year. Seems like there is definitely a season which primes them but it takes the onset of cold wet weather to push them over the edge.
This spring's fawns have been drawn out over several months. The first, a pair of twin bucks, appeared in later May. Usually that's the start of the flood, but we never saw any other than those two for 3-4 weeks, then suddenly a whole bunch showed up, smaller. In the past week and a half, we've seen a smaller, but substantial influx of very tiny new fawns again. Call it 3 waves, 5% of total, 70% of total, and 25% of total. I assume that means the does came into heat in 3 waves, not just 1.
Of the first pair, one died. When it was about a month old, one day it was unable to get up off the ground. It'd been staggering, falling, getting up earlier in the day. It would lurch from the ground, throw it's head forward as if trying to get up, and its tail worked like mad sometimes, but the legs stopped functioning, both front and rear, completely.
The smaller is still around. It's the oldest fawn here by far and its spots are "softer", starting to fade. The biggest bunch are getting real frisky running around like crazy, still have sharply defined spots. The new ones are still gangly/spindly/awkward, but gaining fast.
So I went off on a tangent. Sorry .. ish?
Anyway, last fall's seemed to last a long time. We had a cold rain event at the start of October which seemed to start a little rut activity, then it reversed / stopped, but a bunch of new bucks we'd never seen had appeared and stayed the rest of the fall. I have pictures of them sparring clear through November and into December with rut activity off and on much of the time, no concentration, but also no let-up.
Previous years when I was living elsewhere, we didn't always have an identifiable rut. Any time late October and on, if we got cold rain some afternoon, there'd be bucks chasing does right through traffic in town, but the next day when the rain was gone, there were no deer to be seen at all. Weirdest hunting year I ever had.
Usually I figure if I hunt the last week of October I'll see some pre-rut activity, but not always. It's usually going about Nov 10-12, and usually it goes through almost Thanksgiving, but by the first weekend in Dec, the big bucks are post-rut and damned hard to find again.
Tom