Why Do Dogs Sniff Butts?

Dogs meeting other dogs sniff butts. They don’t generally call out to each other. It’s all a natural type of dog body language used when meeting another dog. Typically, they will sniff each other, often in the body areas where urine and feces exit the body. It’s analogous to reading the neighborhood newspaper and can provide social enrichment for a dog even if other dogs are physically absent at that time.

Dogs Meeting Other Dogs

Dogs learn to recognize individual dogs through their individual scents, which is why dogs will spend time sniffing where other dogs have urinated or defecated. (Yes, it is gross by human standards, but keep in mind that we are essentially “blind and deaf” when it comes to our own sense of smell.)

Canine Sense of Smell

The sense of smell is the dog’s primary sense (the other senses are sight, hearing, taste, and touch). A dog has about 150 million olfactory receptors in his nose (compared to 5 million for us mere humans), and the area that processes that information occupies about 30% of the brain (compared to 5% in humans).

It is this amazingly keen sense of smell that makes dogs such great partners in search and rescue operations and bomb detection. There are also dogs who are trained as service dogs who can sense (smell!) when their human is about to have a seizure, and dogs trained to detect cancer in blood samples and bedbugs in hotel rooms. 

Sniffing Butts and Pheromones

Dogs also have a specialized organ in the roof of the mouth called the vomeronasal organ, the function of which is to detect pheromones, which are chemicals emitted into the air by animals to communicate specific behavioral and emotional states (readiness to mate, fear, relaxation, etc.). Pheromones are produced by glands (including anal glands) and can be found in saliva, urine, and feces.