The sight of one dog licking the inside of another dog’s mouth may look strange to a human observer, but it is a normal and specific form of canine communication. This intimate action is rooted in deep instincts and social necessities that govern relationships between dogs. The behavior serves distinct purposes, including acknowledging social status, reinforcing social bonds, and requesting resources. Understanding the context of this mouth-licking provides valuable insight into the complex, non-verbal language of dogs.
Licking as Appeasement and Submission
One of the primary drivers for a dog to lick another’s mouth is to signal deference and actively reduce tension within a social group. This action functions as a specific type of social signal, often performed by a dog that perceives itself as having a lower status toward a higher-status or more dominant peer.
The act of mouth-licking is categorized as a form of “active submission,” used to greet or appease a social superior. The dog performing the lick often makes its body appear smaller, sometimes lowering its head while looking up to emphasize its subordinate role. By offering this gesture, the dog communicates non-aggression and peaceful intent, which helps prevent potential conflicts from escalating.
This submissive licking is also considered a “calming signal” that serves to diffuse stressful situations between dogs. If a dog feels threatened or anxious, the muzzle-licking gesture communicates a respectful acknowledgment of the other dog’s authority. The dog is essentially saying, “I am not a threat.” The recipient dog accepts the signal by tolerating the gesture, reinforcing social harmony.
Affectionate Grooming and Group Cohesion
Beyond the context of social hierarchy and conflict avoidance, mouth-licking serves a purely social function, reinforcing the bonds of friendship and affiliation between dogs. This behavior is considered a form of mutual grooming that strengthens the relationship between closely bonded individuals, such as littermates or long-term housemates.
The action helps to create and maintain social cohesion, similar to how wolves and other canids engage in mutual grooming. When the behavior occurs between two friendly dogs, it is often a gentle, mutual exchange that signals trust and familiarity.
The physical act of licking can release the hormone oxytocin, contributing to feelings of safety and connection. This bonding behavior is not about submission, but rather an expression of positive regard and affection between individuals. It is a way for dogs to share scents, reinforce their group identity, and display comfort with one another.
Retained Puppy Behavior for Soliciting Resources
The behavior of licking another dog’s mouth has a clear evolutionary origin rooted in early canine life. Young puppies instinctively lick the muzzle and lips of an adult dog, typically the mother, to encourage the regurgitation of partially digested food. This action is a survival mechanism that transitions puppies from nursing to eating solid food.
Even in adult dogs, this instinctual action can persist, becoming a “vestigial” social behavior no longer strictly tied to food. When an adult dog licks the mouth of another, it may be a polite way to solicit attention, comfort, or a tangible resource. This action is a well-mannered request carried over from the puppy’s care-soliciting gestures toward the mother.
This mouth-licking can manifest as a plea for attention from another dog or a request for a share of food if one dog detects the scent of a recent meal. The instinct is so ingrained that it continues as a generalized social tool, used to communicate a subordinate or needy position to a peer. The behavior is an echo of its infantile origins, a communication method that was consistently rewarded in early life.