Why Dogs Sniff Each Other'S Behinds



When you meet someone for the first time, you probably shake hands with the person and subconsciously look to facial expressions or body language for social cues. Meanwhile, you and your new friend look down at each other’s dogs and notice them vigorously sniffing each other’s butts. It is hard not to exchange smiles and wonder why this greeting display is so common amongst dogs.

Though humans interact with the world primarily through sight and communicate primarily through language, dogs approach both of these tasks with their incredible sense of smell. While dogs do rely on other means of communication—for example, communicating through body language—the information that they are able to gain through sniffing each other’s behinds is far more effective as means of introduction. Here are some things that your dogs are discovering and saying to each other as they sniff one another’s behinds in greeting.

The Root of the Behavior

Dogs don’t carry around ID cards, but they do carry around a unique, identifying scent located—you guessed it—in the posterior region. A dog’s personal scent is housed in glands in two small sacs surrounding the anus. The scent is strong enough, and a dog’s sense of smell is strong enough, that at least a small amount of this scent is floating around your dog’s tail at any given time. This scent carries information about a dog’s gender, diet, mood, and personality. Whenever two dogs meet, they look for the other dog’s identifying scent in order to gather information about the person they are meeting.

Though strange to humans, the greeting serves as more than just an information exchange. Dogs establish their relationship through this ritual. The dog to initiate the sniffing becomes the dominant dog in the relationship. Once the dominant dog has identified the second dog, the submissive dog gets a chance to sniff. Though the words ‘dominant’ and ‘submissive’ carry human stigmas, this social process is simply to ensure that dogs in community operate smoothly in a pack. Once the relationship is formed, both the dominant and submissive dog know how to behave around one another, and they usually become comfortable friends. 

Your dog is probably better at smells than you are at faces. If your dog were to smell a friend’s scent, even after several years had passed, it would instantly associate the smell with the specific friend. This is how dogs identify long-lost family members, and how puppies identify their mothers. Whenever dogs go to the bathroom, they release their personal scent onto whatever object or surface they are relieving themselves on. If your dog were to come across this scent on a walk, it would know exactly who the scent belonged to! Additionally, your dog would be able to read key information within the scent that would let it know how the other dog was doing, and what had changed since their last encounter.

Encouraging the Behavior

Though it seems like a strange practice to humans, introduction by politely sniffing beneath the tail is the standard dog greeting. Though the practice may look confused at first, especially between two strongly dominant or two strongly submissive dogs, you should always allow it to run its course. When it comes to smelling each other’s rear ends, dogs know instinctively what to do. Sometimes, the session may get cut short by a growl, or your dog may not want to participate in the greeting, and this is okay too. Your dog may have caught enough wind of the other dog’s scent to know that the relationship simply isn’t going to work out. 

Be careful of pulling dogs away from each other, which is the natural reaction to two opposing runners on the same side of the street. Dogs tend to bark and go for each other not out of aggressiveness, but out of curiosity, and pulling them away from each other can send the wrong message. If you pull your dog away from another dog while it is mid-sniff, your dog might think that the other dog is being extremely rude or aggressive, and this might send your dog into a frenzy. It would be like someone extending their hand to you for a handshake and then pulling away suddenly and walking away from you. That being said, if it becomes apparent that the smelling ritual is leading to aggression, it might be time to separate them anyways, so it is up to your best judgment. 

Other Solutions and Considerations

On top of the pleasure of social interaction, sniffing provides dogs with a sense of calm. They feel grounded and informed, not anxious in the presence of an unfamiliar dog that could be friend or foe. If you have two dogs, you may notice that they sniff each other quickly after every time they are let out to use the bathroom. This is simply their way of catching up, in the same way that you might quickly catch up with a friend after you have both gone to the gym. Dogs check in with each other frequently, just like humans do, and like humans, dogs appreciate the value of friendship and relationship with one another. 


Dogs may not always communicate in ways that are familiar to humans, but if we could understand them, we would find that we have a lot in common with our dogs. Your dog sniffing its friend’s rear end is a lot like you asking your friend if they’ve been out to eat anywhere exciting lately. When you look at it that way, dogs sniffing each other’s butts isn’t so strange. After all, who’s to say that your dog doesn’t judge you for touching paws and barking excitedly with your friends all day?