That makes sense. Could very well be. BUt you mention that he has 2 acres of free running room. Do you live near woods and is it possible that a wild animal of some sort is trying to take up residence in what is otherwise your dog's "territory"? I know our Bob will go out before going to bed for night (he's an indoor dog) and will just stand on the porch and smell up into the air... and if there is a deer or rabbit or anything anywhere near, he goes crazy barking. We often can't see anything, but if I get a flashlight and shine way up on the hillside I can see some beady eyes.

Just might be someone trying to hone in on his territory.