The nose knows.

Deer in different areas react differently. Some smell is most important some sight but I would say hearing is last.

Mule deer would be different than whitetail. They are sight first. Elk would be smell.

Mother-in-law would be.. Nevermind.

a deer can see you and not know what you are.
a deer can hear you and not know what you are.
if a deer smells you, it knows exactly what you are and will react accordingly(either flee or hide).

x2

I'm not sure that smell is the most important. I do feel it becomes less important each year unless you are hunting deep woods. If I had to pick one sense it would be sight combined with hunter movement.

Each year, where most of us hunt, deer become more accustomed to man. The smell of man is common. The sound of man is common. The sight of man is common. The movement of man, when he becomes a predator, is not common.

A man driving a tractor does not bother deer a bit. But let the man climb off that tractor and you have a different story.

Now deep woods deer is a different story. You see you just can't lump deer into a general category. You have to consider all the factors.

I have been studying deer for half a century and I don't know jack about them. I never thought I'd see the day they climbed on my patio and licked my grill.

I'm not sure that smell is the most important. I do feel it becomes less important each year unless you are hunting deep woods. If I had to pick one sense it would be sight combined with hunter movement.

Each year, where most of us hunt, deer become more accustomed to man. The smell of man is common. The sound of man is common. The sight of man is common. The movement of man, when he becomes a predator, is not common.

A man driving a tractor does not bother deer a bit. But let the man climb off that tractor and you have a different story.

Now deep woods deer is a different story. You see you just can't lump deer into a general category. You have to consider all the factors.

I have been studying deer for half a century and I don't know jack about them. I never thought I'd see the day they climbed on my patio and licked my grill.

Most prey animals have an uncanny ability to sense danger! Thats why the big bucks walk right under BSK, he takes his bow and they think they are safe

John is right. Animals can detect the smallest behavioral changes in humans and other animals. It's part of their survival skill. Are animals born with that skill? No they learn it from their mother, like many other things.

How keen that sense is can be best shown with an example of my wife and me. My wife is a photographer and when she takes pictures of wildlife she talks to the animals in a soothing voice, walks toward them, stands still then walks some more. With that tactic she can get very close to deer without alarming them. While she tries to get closer she never looks directly at the animals. Unbeknown to her she mimics deer browsing behavior. She told me that she just copied the way I walk among the tigers and elephants.

On the other hand if I try to walk up to deer I think like a hunter and the deer run. Why? Can they read my mind? No they can't but they pick up on the tiniest behavioral changes, so small that we do not notice them, but deer and other animals do.