Dogs Who Love to Lick Human Feet

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

My dog, Frodo, loves to lick my feet. I think he does it because he likes me but my girlfriend says he does it because my feet smell. Which is it?

No scientific studies of canine foot fetishes exist, but what we know about canine behavior and the human-canine bond suggests that both answers may possess an element of truth. That, in turn, means we must examine both canine and human contributions to this display.

Previously we discussed pheromones, those incredibly powerful chemicals that animals as diverse as ants and wolves use to communicate. Not only do animals pack a tremendous amount of information into these chemicals, only those who possess the proper receptors can receive the message. Many species secrete pheromones from glands in their feet which they use to mark their territories as well as to find their way. When others zero in on such scents, they may lick the object and/or their noses to enhance the processing of this scent data.

Although social animals such as dogs don’t depend as much on the foot-form of communication/marking like more solitary species such as cats, two foot-related domestic canine behaviors suggest that feet play or played an important role in the canine behavioral repertoire. First, the fact that many dogs resist others handling their paws indicates that dogs take a protective view toward this part of their anatomy. Admittedly, this might result because dogs depend on their feet for locomotion. However, many dogs who resist having their feet manipulated will readily permit handling of the rest of their legs. This would seem to imply that the feet themselves carry the behavioral charge.

Second, dogs who mark with urine or stool also may scratch the ground with their hind paws. Not only does this provide a visual mark, but the scent from the feet could alter the message communicated. Even though few studies of canine pheromone communication exist, we do know that the pheromones secreted by the cat’s facial glands communicate a more positive “This is mine” message compared to the more combative “I’ll fight you if I catch you here” notice given in the marking animal’s urine. Perhaps dogs who scratch after they mark use this behavior the same way we might use a wink or threatening gesture following a blustery outburst: to soften or strengthen the original meaning of the message.

Turning to the human half of the equation, do humans communicate using pheromones? For a long time scientists and the general public believed that any odors humans emitted resulted from problems—such as disease or a failure to practice good hygiene—rather than constituted part of our normal physiology. Because we viewed “body” odor as wrong, the idea that we might produce odors that we couldn’t smell that could affect our behavior struck most as totally unacceptable. Consequently, scientists denied that we produced pheromones and also that we possessed the necessary physical apparatus to detect them. However, recent research indicates that we both produce and can detect such substances, and that these substances can alter our physiology and behavior as dramatically as similar compounds alter that of animals. Alas for dog-lovers, most of the research focuses on pheromones that affect mood or reproductive cycles, with those we emit from our feet receiving little or no attention.

Still, even though science may pay little attention to human chemical footnotes, for sure many dogs do. Moreover, some dogs find the feet of some people more tantalizing, just as some of us find certain human feet smellier than others. Traditionally the conventional wisdom said that dogs chewed shoes because the leather elicited memories of a time in their wild past when they teethed on the hide remnants of their prey. However, sufficient numbers of dogs chew shoes, slippers, and socks with nary a whisper of leather (or any other natural product) about them: Could the scent message imparted to those objects by their owners’ feet serve as the more likely canine attractant in those people’s absence or in times of canine stress?

Whatever the message owners of foot-loving dogs unknowingly communicate, the blissful look on these animals’ faces indicates that the dogs, at least,think it’s a good one.