They do seem to know when hunting season rolls around. In my experience it has a lot to do with routine. Deer are fine with about anything as long as they're use to it. For instance, deer in my backyard ignore me, noise from the TV or radio when the windows are open, the garage door going up and down, my vehicles coming and going. They walk close enough to open doors and windows that you can not only hear them breathe but you can smell them. (visitors get a kick out of that) They'll be grazing a few feet from the A/C unit when it kicks on and they don't even flinch. However, you bring in something different in the yard, a different vehicle shows up in the driveway, you move an object or even park your vehicle in a slightly different position and they notice. It's a big deal to them. I left a propane cylinder out in the back yard a few weeks ago and you should have seen the reaction. They'd cautiously circle all around it, stomp their feet, run back and forth. Pretty soon they'd slowly creep up and sniff it or taste it and then run away again. Took a day or two before they figured out it wasn't gonna eat them and they went back to normal. They do the same thing when i add a new spinner or target to my backyard .22 plinking range. It's the same way in the timber. I can ride my ATV back there and the deer will move a few yards away but they aren't particularly worried about me or the noise. Same way with a tractor. They'll walk or bounce a few yards away and then go about their business. You ride back there on a 2-stroke ATV or motorcycle or even walk back there and deer start running every which direction. It is different and different spooks them.