Why Do Dogs Sniff Each Other’s Bottoms? It’s More Complicated Than You Might Imagine

Why do dogs sniff each other’s butts? The answer to that question is a bit more complicated than you might imagine.

According to a new video from the American Chemical Society (above), it’s all about one canine literally sniffing out important information about the other–its gender, emotional state, diet, and more.

“Think of it kind of like speaking with chemicals,” the video’s narrator says, referring to the glandular secretions released by glands in a dog’s anal sac. “In fact, this butt-sniffing action is just one of many examples of chemical communication in the animal kingdom.”

Of course, a dog’s sense of smell is famously acute–10,000 to 100,000 times more acute than our own, according to the video. How can the sniffer make sense of the glandular secretions released by the sniffee’s anal sac–without the poopy smell getting in the way?

Dogs have a second olfactory system that’s known as the Jacobson’s organ. Its nerves direct the chemical information it detects directly to the brain so there’s no interference from other odors.

Now you know everything you wanted to know about Fido’s anal fascination–and more.