I'm having the same problem. Every time I let Dexter outside, he lets out a very loud howl and then runs around snuffling the ground. There is a fox that roams the area at night, so I'm guessing that's the reason. But it's really frustrating having him bark every time I let him out! I've tried letting him out the front, even leashing him up and personally walking him out. Our trainer suggested using white distilled vinegar. Put some in a small spray bottle and carry it around with you. Then whenever he barks, spray him in the face. It stings for a few seconds, but is not harmful. I've only been using the vinegar method for a few days now, so not sure if it's helping yet.