Dogs lick other dogs' mouths for several reasons and deciphering this behavior may require some investigation. When does the licking happen? In what context? What is the dog's accompanying body language like? And most of all, how does the other dog react?
Supervising the interactions of dogs is always important. Some dogs can sometimes engage in persistent behaviors and may ignore the several "go away' or "stop it" signs the other dog is delivering. This can lead to squabbles, and sometimes, even serious fights.
A Behavior Reminiscent of Puppyhood
Licking other dogs' mouths is a behavior that is reminiscent of when puppies were in the litter with their littermates and mom. To be exact, this behavior seen in puppies may be categorized as an et-epimeletic behavior.
In animal behavior, the term et-epimeletic means seeking care or attention, as it often happens in most young animals. Born with their eyes sealed, ears closed and unable to regulate their temperatures, day-old puppies engage in several behaviors that trigger care-taking behaviors in their mothers.
In particular, puppies vocalize when they are cold or hungry or when they are separated from their moms. These behaviors trigger care-taking behaviors from mom, which are known as epimeletic behaviors.
As puppies grow, they go through a phase where they will transition from mom's milk to more solid foods. This phase is known as weaning. In a domestic setting, breeders, help puppies transition by offering puppy gruel and puppy mush.
In a wild setting though, and prior to being domesticated, puppies used to lick their mother's lips and mouth to evoke her to regurgitate semi-digested food for them (breeders claim to still witness this behavior every now and then). This may sound odd, but this helped the pups transition from a diet of exclusive milk to one based on meat from prey.
Interestingly, this behavior (the mouth-licking behavior) tends to persist past the weaning phase and becomes a puppy's and dogs' way to greet other dogs (and sometimes people too!)
Gathering Some Information
Many dogs who lick other dogs' mouths are often doing so to obtain information. Dogs have a very strong sense of smell and they rely on their powerful noses to gather information about their surroundings.
In particular, a study, published in the Journal of Animal Behavior and conducted by Marianne Heberlein and Dennis Turner at the Institute of Zoology at the University of Zurich, found that the behavior of nose touching in dogs may occur as way to gather information about the other dogs' feedings.
It's as if by nose touching, dogs are inquiring and saying something along the lines of "Howdy, have you found any tasty treats around here?" Of course, the answer lies within the other dog's breath. While we may just smell doggy breath, dogs are likely to smell that kibble basted with a meat-flavored savory sauce the dog enjoyed just hours earlier.
Licking another dog's mouth is certainly a more intrusive approach compared to nose touching though, and therefore, it's likely to provide even more information. Sometimes dogs may willingly open their mouths for the other dog to inspect. This allows the other dog to, not only smell the other dog's breath, but perhaps even enjoy something tasty to lick or eat too!!
Of course, the behavior can get quite reinforcing and prone to repeating if the licking dog happens to routinely find some tasty food remnants. This is likely to occur right after eating or if the dog being licked has lots of facial hairs (think dogs with beards and goatees such as schnauzers and bearded collies) which attract remnants of tasty bits of food.
Those Facial Pheromones
Interestingly, dogs are known to have several body parts that secrete pheromones. Pheromones are simply volatile chemical substances that are secreted for the purpose of releasing information that affects other dogs/animals who detect them.
Dogs have a special organ meant to detect pheromones that's known as the Jacobson organ. Also known as the vomeronasal organ, the Jacobson organ is a patch of sensory cells that's found inside the dog's nasal cavity and opening in the upper part of the mouth.
When dogs sniff and lick other dogs' mouths they may therefore be attracted to the labial area (lip area). The labial area in dogs has been known for releasing pheromones, explains Dr. Bonnie V. G. Beaver in the book: "Canine Behavior: Insights and Answers."
Veterinary behaviorist Karen Overall in the book: "Manual of Clinical Behavioral Medicine for Dogs and Cats" refers to the behavior of licking other dogs' mouths as deferential, basically, a way for expressing respect. Dr. Bonnie Beaver instead refers to it as relating to social status, with the higher ranking dogs "smelling" the lower ranking dogs.
Until dogs can talk, we can only make assumption as to what is going on really in a dog's mind when mouth-licking. Perhaps rather than labeling the behavior as a sign of social status or submission, it's more productive looking at how the behavior presents, the context in which it happens and the accompanying body language.
Some dogs may walk with confidence, and after eating a goodie, may purposely breathe out samples to encourage other dogs to investigate their mouths as if saying: "Look what I found, now am I great or what?"
Some other dogs, on the other hand, may become obnoxious at times, pestering other dogs around forcing them to have their mouths inspected. Other times, mouth-licking behavior may be seen after a scuffle, almost as a way for apologizing for any possibly perceived wrongdoing.
Possible Medical Issues
Dogs have been known for being capable of detecting diseases as serious as cancer. According to UC Davis Health System, dogs have shown the capability of recognizing melanomas as well as bladder, lung, breast and ovarian cancers in humans.
Not surprisingly, when dogs develop a sudden interest in certain body parts, it may be worthy investigating whether there may be something going on in the health department. Dogs are pretty good in knowing when other dogs are ill by just their scent.
Perhaps there's a dental issue that is causing odors in the mouths or the gums are inflamed. Perhaps there is a piece of bone lodged in between teeth.
Now That You Know...
As seen, the behavior of licking other dogs mouths is quite common among canines and may occur for a variety of reasons. In several cases, it's an occasional behavior and the other dog seems to enjoy it or at least tolerate it for a bit. It's OK to let them be if the behavior doesn't seem to cause problems and it's not persistent.
However, sometimes things may get out of hand. It's important to keep an eye on the dogs and ensure that the licking dog doesn't get too carried away. Watch for signs of the other dog growing tired of the behavior. Obnoxious licking can be a very irritating behavior to some dogs. On top of this, persistent licking with a rough tongue may trigger skin problems and infections in the long run. Following are some tips on tackling this issue.
- Have the dog (having the mouth licked often) see the vet to rule out any possible medical problems. Many dogs are prone to gum and dental issues. According to research, most dogs older than 5 have significant periodontitis.
- Watch for cut-off signals from the dog being licked. Turning the head, moving away and yawning may be signs that the dog is getting annoyed. Next, a growl may be emitted, and then, there may be risk for a bite. Of course, not all dogs communicate in such linear ways and some may go straight to just growling and biting.
- Redirect the licking behavior to an alternate behavior. For instance, tell your dog "leave it" as soon as you notice his intent and redirect him to an alternate behavior such as targeting your hand. Make sure to praise lavishly and reward. Alternatively, you can try to redirect to a chew toy the other dog isn't very interested in.
- Keep the dogs separated with a baby gate when you cannot monitor and redirect. Alternatively, you can try using a remote monitoring system to catch your dog in the act and redirect as needed.
- Consult with a dog behavior professional if things seem to be getting out of hand.