I'm sure this isn't news to most country drivers, but I have been in a car with some city friends who weren't going to slow down after they saw a single deer cross the road up ahead. If you see one cross, slow down and be ready for a few more!
Sure enough a couple more went across and if we hadn't slowed, we would've going 60 right through them...
Every time I see one, I slow down and look, and at least around here there is almost always a few more.
We lost a beloved station wagon to a deer that jumped up from below the road on a hillside; there was no chance to see it beforehand and driving 35mph was still too fast/too close.
In the local foothills September, October, November are the months for deer doing stupid things. Bucks chasing does, and does spooking from bucks, all lead to deer popping into the local roads quickly.
On the one that got away; shortly after getting my driver's license, I was driving quickly (around 50-ish) in my parents nearly new car from the city out to the farm on the county roads. Similar scenario, an unseen and unseeable deer jumped up from below the road into my lane. I stood on the four wheel disk brakes, and swerved into the other lane, when, Surprise!, a second deer jumps up into that lane, even closer to me. While still standing on the brakes, I swerved back into the other lane, as the drop off on both sides of the road were too steep to contemplate going off the pavement. When the car stopped, the bumper was about three inches away from the first deer who hadn't budged an inch. Once the car stopped, it was about two nanoseconds before the deer took off, diving through the barbed wire fence, leaving a small burst of deer fuzz behind.
Yes, I never have driven that quickly in rural twilight again. Live and learn.
All the best,
Peter