"Smelling each others' butts is just another example of chemical communication in the animal kingdom. It's like 'speaking with chemicals,' and that's how dogs ask about another dog's diet, gender, and emotional state." according to iflscience.com. "He's a fellar (didn't need to sniff his poop chute when I can see his nards), he ate Raisin Bran this morning >gags<, and he's irritated because I'm sniffin' his loaf pincher." Aren't you glad we don't do this?