DEAR PET TALK: Why do dogs roll onto their backs? Doesn’t that put them in a vulnerable position? —Dog Lover DEAR DOG LOVER: It definitely does and when they do that, they’re telling you — in all caps, if you will — I’M NOT IN CHARGE, PLEASE RUB MY BELLY! Dogs, like all canids, have sophisticated and complex behavioral habits and rolling onto their backs can be the result of multiple stimuli. First, showing great joy. A dog will spontaneously go from sitting or standing to just flopping over,...