Shed,

A lot of people think the deer see the IR because they are often looking in the direction of the camera.
They may be able to see something, but IMHO I think on a quiet day the primarily hear the "click"
of the shutter instead of see the IR flash. For example, we've got a bunch of daytime pictures
that are a blur from the deer jumping in reaction to the cam taking the picture. I also noticed
that after a while it didn't seem to affect the same deer as much.