Woods, I did some more checking, remember I am electronically challenged, which means dumb. I read that PIR which is used in sensors does not emit any beam, they pickup and collect infrared waves from what is passing by it and send that to the sensor which trips the camera. Thus the deer has nothing to detect because there is no beam to break or see. Maybe the camera click taking the picture is what he is keying on and knows where to stop and turn around. Just a thought.