This is a question that has intrigued boys and girls from around the world for as long as anyone can remember. Our explanation is equally old. It's a fable designed to provide a not-too-serious reason for dogs to sniff one another's bums. It's a little bit silly, but it is also compelling. Above all, it's an easy explanation to give to small children wanting to know why dogs have this peculiar habit. It's a `must have' resource for most parents!