You’ve probably wondered it yourself, furrowing your brow as you watched two dogs meet by sticking their face into the other’s rear end: Why are they sniffing each other’s back sides?

Image source: YouTube

Image source: YouTube

Leave it to the YouTube channel Reactions, which is produced by the American Chemical Society, to explain why this happens from a scientific standpoint.

“It’s a somewhat silly question with a surprisingly complex answer,” Reactions wrote in its description of the video. “This behavior is just one of many interesting forms of chemical communication in the animal kingdom.”

“When a dog smells another dog’s butt, it’s actually collecting a bunch of information about the other dog: it’s diet, it’s gender, it’s emotional state and so on,” Reaction’s host said in the video, which goes into detail about the chemicals secreted from glands around the dog’s tail end and how there’s a component in the dog’s nose that allows it to only pick up chemical signals. “Think of it kind of like speaking in chemicals.”

For a full explanation about why dogs “sniff each other’s butts,” watch the short video:

(H/T: Gizmodo)

Front page image via Shutterstock.