The Smiling Canine

(Originally written for DogWatch, a newsletter for the general public from the Cornell University College of Veterinary Medicine)

During the holidays I entertain a lot more than usual and my dog, Molly, will greet some visitors with what looks like a smile. A friend told me this is a sign of submission, but Molly seems so happy when she does it, plus she doesn’t do it to people with whom she’s obviously uncomfortable. So, what does that smile mean?

We know that evolution typically rewards those individuals who get the job done the best way using the least about of energy, and that holds true for communication, too. Because of this, animal communication runs the gamut from obvious “What you see is what you get” messages, to highly ritualistic displays that may have little or nothing to do with their original meaning, to cues so subtle you’d miss them if you didn’t know enough to look for them. The ability to read those signals both from one’s own species as well as those of other species directly related to one’s well-being becomes part of the legacy passed from one generation of wild animals to the next.

If we look at Molly’s smile in terms of her wild roots, where might it originate? The more grimace than smile-like display a submissive animal uses to greet a more dominant one first comes to mind. Compared to the wide-eyed, lips pulled straight back, full tooth exposure, erect-eared, and forward-directed, fully alert body posture of a dominant animal, a submissive posture communicates a much more introverted message. Although submissive animals may expose their teeth, they also drop the lower jaws slightly, curl their lips upward, and close their eyes somewhat so that they may appear to be squinting. These animals may also flatten their ears and hold their heads and bodies low and curved to the side.

Additionally, though, we can’t overlook the fact that Molly’s display may have evolved from the Flehmen reaction. Many mammals possess a second, more primitive olfactory system that they use to process the pheromones that communicate crucial survival messages, such as those related to possible mates and prey. Rather than traveling to the olfactory lobes of the brain via the nose for processing like most scent data, these very important messages are carried to the brain via a duct that begins in a bump behind the animal’s upper incisors. Animals using this system assume a characteristic facial expression geared to enhance the transmission of this data while simultaneously blocking any other that might interfere with it. This typically involves curling the upper lip upward sufficiently to block the nostrils, dropping the lower jaw slightly, and closing the eyes and flattening the ears somewhat.

Although the body postures associated with submission and the Flehmen reaction communicate quite different wild animal messages, remember that conservation of energy remains the key to evolutionary success. If a situation arises in which an animal wants to communicate a new message, it takes less energy to adapt already existing behaviors than to develop brand new ones. Not only that, adapting a behavior that is even remotely related to the new message will help those who receive it to understand the new meaning. Thus, perhaps once those first wild dogs gained the necessary information regarding their cohorts’ rank using the Flehmen reaction, they merely signaled this with upturned lips and other characteristic facial expressions rather than go through the whole sniffing process.

As if wild animal communication weren’t complex enough, domestication adds its own little quirks to the process. Unlike her wild ancestors, Molly must communicate with members of a completely different species—humans—more often than with her own kind. Additionally, she interacts quite intimately with some of these aliens on a daily basis, whereas she only encounters others once or twice or year, or maybe only once or twice in her lifetime. And furthermore, she must communicate with them using an eon’s old system passed down from her canine ancestors.

Because of this, we can appreciate why Molly and other canine companions might display behaviors that don’t quite fit the wild dog mold. Some dogs smile while they crouch; others smile while they leap and dance wildly. Some smile only for men; others smile only for women. Some rarely, if ever smile voluntarily, but if you rub them in particular spots along the backbone, they will.

Each dog comes to us with a basic canine ancestral “language” which has been further modified by domestication and the animal’s breed. As our pets interact with us and any other humans and animals which they encounter in our households and other environments, that language becomes even more refined and unique. When Molly adds her distinctive holiday greeting to her owner’s, it represents the end-product of this wondrous process. What an enchanting gift for those who appreciate all that went into its creation!