Sight for me. I agree with @redbeard,squirrels can mess with you as far as sound goes. On a gun opener a few years back I had a squirrel close by making a ruckus,running back and forth. So five minutes later I heard more crunching and figured it was the squirrel. I was wrong,a buck was cruising by and my gun was leaning against a tree I was sitting by. I almost didn't manage to pick it up before the buck was past.