The American Chemical Society is at it once again with an informative video based on chemistry. This episode of its Reactions series isn't for the easily squeamish, however. The lesson today: Why do dogs sniff each others butts.
The short answer -- it's a form of chemical communication and Fido is in information gathering mode when he starts to sniff those posterior regions. What he's finding is a bunch of short-chain acids.
Once you get past the ewwww factor, it's a pretty informative two-and-a-half minutes.