My boy Luke huffs; it is the best way I can describe it. It is a greeting behavior that he displays to people he likes. I have not seen another dog that does this but I'm sure that they are out there. This huffing behavior started at a very young age as an open mouth greeting.
Open mouth greetings can be disconcerting to some especially when added to a highly reactive dog. This means that not only is the mouth open but chances are that the dog is jumping a s well. Luke has nailed several people in the face with his open mouth in his younger years which was a problem. But it was not a negative; the outcome was negative but the meaning was purely positive.
About a year ago I was watching a documentary on tigers. The guy in with the tigers was explaining that tigers chuff. A chuff is a sound tigers make to say hello to each other. They also make this sound just to tell you they're in a good mood. Visually; it looked like what Luke does but when I took a closer look, a tigers chuff is more of a universal tiger communication. A chuff seems to be more related to a sound than an action.
When Luke huffs, his mouth is held open in a relaxed manner. His lips are pulled down almost over his teeth and his tongue is pulled up from the back. His breathing is heavy and very audible. This is a clear communication of happiness. The rest of his body concurs that this is a positive canine behavior.
Often when Luke is huffing he is also rubbing up against whoever the huffing is directed at. His head is held to the side and there is soft eye contact. We have come to enjoy this communication as it is a very pleasurable experience for both Luke and for us.
Anyone who knows Luke knows that receiving the open mouth huffing is a good thing. Each dog is an individual and although there are man universal canine body behaviors; some are more of an individual style. These if you do not understand them can be quite confusing. That is why it is imperative to watch the entire package and not just one factor of a behavior.
I will try to capture an image of huffing.