Snake in the grass

This guy lives somewhere on the property, but I don't know where and probably will never find out.  It's a black snake, very common, very docile and very helpful at keeping the field mouse population in check. 

 

About 4 feet long, I see him every few days moving gracefully between the oak trees in front and on either side of the house.  I've never seen him in the back in the open areas.  If you walk up close to him he'll stop moving and if you then stand very still, he will eventually start moving again, usually a little closer to you to check you out and then move on going where snakes go to do what snakes do.