Butt-sniffing behaviour in dogs is just one of many examples of chemical communication in the animal kingdom, researchers say.
A new video released by the American Chemical Society explains why dogs smell each other's behinds.
According to the video, this behaviour helps one canine sniff 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," the narrator was quoted as saying by 'The Huffington Post'.
The video also explains how the sniffer can make sense of the glandular secretions released by the sniffee's anal sac without other smells getting in the way.
Dogs have a second olfactory system 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 odours, according to the video.