What is a kiss? To a scientist it is “oral to oral contact with mouth movement without food transfer.” Doesn’t that sound pleasant? On this definition, mouth-to-mouth resuscitation would be kissing. I think kissing must also involve affection or pleasure.
Do animals kiss? Great apes and other primates do. Kissing, in fact, has been around for a long time. Scientists think Neanderthals (homo neanderthalensis) might have kissed as far back as 20 million years ago. They shared saliva, at least. That could indicate kissing, or food sharing, or both. Neanderthals might even have kissed humans (homo sapiens). Dental DNA indicates humans and Neanderthals share mouth bacteria.
Scientists have observed behaviors similar to kissing in mammals, birds, fish and insects. Puffins, for example, mate for life but spend much of their lives separated at sea. They make land in spring and summer to mate and raise a chick among colonies of other puffins. Once on land, puffin pairs find each other and rub their colorful beaks together, a practice called billing. Billing is an important part of the courtship process, solidifying the pair’s connection after a long absence. Is billing kissing? I’ll let you decide.
We are all familiar with eastern gray squirrels. Have you ever seen them kiss? Sometimes squirrels rub their noses or mouths together. Are they kissing? Smelling? Whispering? The behavior likely occurs because squirrels have apocrine glands in the skin surrounding their mouths. (Humans have apocrine glands in our armpits.) By touching their noses or faces together, squirrels share sensory information about their age, status, reproductive state, kinship and so on. Scents are more important to squirrels than to humans. When a squirrel grooms itself, it rubs its front paws across its face and mouth to collect scents to spread over the rest of its body. All gray squirrels, no matter their age or sex, rub their cheeks on tree branches as they wander about their home range. This behavior constitutes squirrel ID.
The northern cardinals you see in your backyard during January and February snowstorms could be the same ones you will see in the spring. As part of his courting process, the male brings the female seeds. He cracks them open before gently offering them to her. (Who said chivalry was dead?) By flapping her wings and opening her beak (just as hatchlings do), the female signals to the male to bring her more food. The male responds by bringing seeds as often as every 15 seconds. Scientists think the ritual helps establish a pair bond; it also demonstrates to the female that the male will be a good provider. Later, when the female cannot forage because she is incubating her eggs, the male continues to bring her food. Passing food, beak-to-beak, begins as a courtship behavior and becomes part of the daily grind, so to speak, once several chicks hatch and beg to be fed.
Rock doves (pigeons, to you and me) mate for life, although their life expectancy in the wild lasts only about three years. During their courtship, a male inflates his neck feathers, coos, bows and pirouettes in front of the female. If interested, the female inserts her beak into the male’s beak, and he regurgitates food for her from a pouch in his neck (the crop). How romantic! This behavior provides the female with extra nutrients she may need to lay eggs. Courtship behavior can occur at any time of year because pigeons do not rely on seasonal foods, such as seeds and insects, to feed their young. Instead, they produce nourishing “milk” in the crop their youngsters feed on.
Who hasn’t seen mute swans mirroring each other, with their long necks forming a heart shape and their beaks touching? Mute swans, mating for life, seem quite attached to each other. During courtship, they dip their heads in water in unison and preen themselves. They speed up, and perform this ritual faster and faster. Then the swans face each other and press their breasts together, synchronically raising and lowering their necks. They intertwine their necks, and mate. Swans go through this ritual often during the breeding season. Despite their name, mute swans hiss and grunt during courtship. Some scientists think this behavior helps strengthen their lifelong pair bond. The couple raises their young together. If one parent dies, the other takes over.
Television and other media let us surmise that kissing is a universal human trait. Actually, less than half of human cultures kiss romantically. A study in American Anthropologist documented kissing behavior in 168 cultures. Only 46 percent engaged in the romantic kind.
If not all humans kiss, what does this imply about kissing among animals? Many animal pairs express affection for each other. They also engage in food sharing or nuzzling behaviors, but whether they amount to smooching is anyone’s guess. Happy Valentine’s Day.
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