I think part of this may have to do with increased hunting pressure and human interaction. But I also think that they tend to blow/snort more if you catch them completey off guard and they have no idea what you are or where you are. They just know that something's there that's not right.
As we all know, deer rely on their smell, hearing, and to a lesser extent eyesight. If they hear a sound, but they can't smell or see it, they may very well snort/blow to ID it. Same if they see something but can't smell or hear it. But if they smell you...you will most likely never see or hear them at all.
I have also learned firsthand that deer who live in close proximity to humans will tolerate ALL of these detections to their senses as long as YOU ARE WHERE YOU ARE "SUPPOSED" TO BE, in the deer's context.
I can walk from my house to my barn twice a day everyday to feed the horses and have deer on my front lawn 30 yards away that will watch me but not flee. If I walk around the barn and come from the OTHER direction they high tail it out of there blowing, snorting and farting like satan himself was after them!
Offer No Apologies.....
NRA Endowment Life Member