If dogs have such a keen sense of smell, why do they spend so much time with their noses near each other's rear ends? This video gives a quick introduction to dog butt science and explains why their noses aren't overwhelmed by the smell of poop.

The American Chemical Society explains what chemicals dogs detect when they put nose to butt and what kind of information they're getting out of these smelly encounters. Chemical communication is pretty fascinating, especially the way that dogs are built to filter useful smells out of all that anal odor.

[via The Mary Sue]