At the risk of making myself sound like a drunk...(I am not, in fact I can only drink one or 2 drinks and feel the effects heavily
).
If I am at home with friends, and we are having a few drinks - even around a fire outside - my Bongo recognizes immediately the moment I have had "enough". He will come grab my hand until I take his collar, and he leads me straight to my bed! I didn't intentionally train him for this, but I do have a habit, when I have had "enough", to at least put the dogs away for the night and sometimes go to bed myself. I think he has learned to smell the level of alcohol in my blood - and knows it is time for his dinner and bed time! Funny thing is, I don't drink too often - they just learn so fast! Maybe this has some application in law enforcement for drunk drivers!
