The Invisible Scent-sational Companion Animals

One of the first harbingers of early spring we humans often miss is the dramatic increase in the outdoor scent load.  Once we process the smell of grimy, slushy, snow and mud—often negatively—what else is there to smell? But most of our naturally nosier dogs and cats don’t see it that way. To them, the lengthening days signal the arrival of a scent wave that will reach tsunami proportions before it begins to ebb again. To get some idea what this could mean to a dog, I often send this brief video to my clients:

I know of no comparable video regarding cats. However, their sense of smell most likely equals dogs and possibly surpasses thanks to their solitary, nocturnal, and predatory heritage.

Contemporary human awareness of the role the sense of smell, a.k.a. olfaction, plays in companion animal behavior greatly lags our awareness of the other senses. This occurs even though olfaction ranks as the primary sense in all mammals. Perhaps our cultural and media emphasis on what we see or how others or objects look to us led us to consciously or subconsciously demote olfactory input. Or maybe because other mammals so outdid us in this area, we chose to view this as a lesser skill.

That olfaction could represent a more primitive (and thus more deeply entrenched and survival-enhancing) perceptual ability than our color-and detail-enriched vision seems likely, given the experiences of people without it. People with congenital or acquired anosmia, i.e., having no sense of smell, commonly speak of feeling vulnerable. In this NPR article, a young woman speaks of her fears regarding moving into a place of her own. While most of us might worry about the ugly color of the walls or creepy-looking old lady who lives in the next apartment, she’s far more concerned about not realizing there’s a gas leak in her home. Or eating or drinking something spoiled.

Research indicates that odors also trigger emotion and memory, another limitation faced by those with anosmia. For many people the scent of pumpkin pie or pine decades later may evoke all the warm feelings and memories of special holidays better than images of the same event. Similarly, our minds forever may link a scent with a painful experience—e.g., the scent of the cologne worn by the supervisor who publicly humiliated us, the odor of the nachos we ate right before we got hit with a nasty intestinal bug.  While it’s tempting to believe we could do without those negative scent-triggered memories, these and the positive ones also could trigger changes in our behavior that could enhance our well-being.

A similar relationship exists between scent, memory, emotion, and behavior in non-human mammals. However, because of their superior olfactory sensitivity, they depend on olfaction for their survival more than the average person living in suburbia. A partial table of contents from the recently released Olfaction in Animal Behaviour and Welfare edited by Birte Lindstrom Nielson provides a useful reminder of the critical functions where olfaction affects animal well-being:

Chapter 6. The role of olfaction in feeding and foraging—Marije Oostinder, Norwegian University of Life Science, Norway
Chapter 7. The role of olfaction in mate selection and reproductive behaviour—Luisa Amo, Spanish National Research Council, Spain
Chapter 8. The role of olfaction for parental care and offspring survival—Frederic Levy, INRA, France and Raymond Nowak, INRA, France
Chapter 9. The role of olfaction in disease detection and prevention—Tadeusz Jezierski
Chapter 10. The role of olfaction in relation to stress and fear—Vincent Bombail, INRA, France
Chapter 11. The role of olfaction in animal housing and as enrichment—Deborah Wells, Queens University Belfast, UK
While we might dismiss these links as irrelevant to the behavior and welfare of spayed or neutered companion animals in the average companion animal household, is that really true? Can we safely adopt  an “If I don’t smell it, they don’t smell it” or “If I think it smells good (or bad), they agree” approach to scents until circumstances prove us wrong? Let’s consider a few examples.

Heading the scent-related list this time of year are pet dogs and cats marking with urine or stool in response to the increased scent messages left by free-roaming domestic animals and wildlife around their homes. The pets leave their own odiferous replies, also embellished with pheromones that communicate their identity and intention to protect that space if necessary. Meanwhile, John or Mary Petowner smell something vile and remove all traces to their satisfaction. To do so, they reach for their favorite cleaning product with its fresh, clean scent.

But when the animal continues marking in that same place long after any threat has moved on, the Petowners discover that, even though the area smelled as fresh as a summer breeze to them, their pets didn’t get the same olfactory message. Scent molecules beyond human perception still lingered and lured the dog or cat back to that location. At that point, the Petowners get a crash course in the proper clean-up of canine and feline urine and stool.

Another crash course in canine and feline olfactory sensitivity may occur when the Petowners move into a home previous occupied by those who also had animals. Next thing the new residents know, their pets contribute their own version of the Welcome Wagon: they pee in the corner of the living room or the middle of the family room. Once again, the house or apartment they thought smelled fresh as spring breeze didn’t smell that way to their pets.

Digression: As soon as I wrote that, I had a mental image of some ethologically challenged product developer creating an air freshener or cleaning product with a scent composed of all the natural scent molecules present in the natural spring environment. In this fantasy, the folks in advertising and marketing create slick campaigns designed to appeal to all-natural consumers seeking to bring nature into their homes. Alas, the product turns out to be too natural for consumers’ pets. One whiff of the new product and dogs and cats everywhere begin succumbing to a myriad of stress-related behaviors, including marking with stool and urine.

But returning to reality, another scent-related challenge may arise when cats fed the same food from a young age may require a dietary change later in life. Perhaps the cat becomes allergic to something in the food or develops a medical problem that requires a special diet. Because scent plays such a vital role in feline appetite stimulation and their solitary, predatory heritage makes cats more neophobic—i.e., leery of new things—changes often must be made very, very gradually. Otherwise, if cats become suspicious, they’ll stop eating completely. And yes, this sounds overly cautious until you realize that it’s safer for solitary animals to pass on a meal than risk eating a tainted one.

Compare the feline approach to making diet changes in dogs where a quarter of the old food is replaced with the new over a 4-week period. This isn’t an issue of overcoming scent-aversion as it is in cats. It’s to avoid the diarrhea that may occur when the gut doesn’t enough time to adjust to the new diet.

Another cat-related scent challenge involves cats with upper respiratory problems. Anyone who’s had such a cat soon discovers the role the ability to smell their food plays in feline willingness to eat it.  I can recall cases of kittens and cats with stuffy noses who would ignore a bowl of their favorite canned food, but if you put that same food in their mouths they’d eat it. If was as if, lacking the scent- trigger, they’d forgotten about eating until the taste and texture of the food triggered their appetites.

When properly used, pheromones—communicating hormones animals can smell but humans can’t—such as Adaptil and Feliway may help decrease canine and feline stress. One study demonstrated that the essential oils lavender, chamomile, rosemary, and peppermint may calm or stimulate shelter dog behavior. While I agree with the Irish researchers that potential adopters would find calm and relaxed dogs more desirable, I’m not sure how many American shelters and adopters would share this view. There seem to be a lot of people who find stressed dogs who jump on cage and run doors and gobble treats appealing for some reason.

As in all species, the olfactory ability of dogs and cats spans the spectrum. Just as not all people possess the olfactory skills of a fragrance chemist or experienced sommelier, not all dogs possess those of a bloodhound. While some pet cats make an immediate mouse scent-prey connection, others may show little response to such odors. Many healthy cats may make a major production out of accepting anything new in their diets whereas diabetic cats and those with other illnesses may eat everything offered and look for more.

And finally, we have those transported cats and dogs (including puppies and kittens) who experience dramatic changes in their scent environments during a relatively short period of time. Every change in location, every form of transportation between those locations assaults these animals with unknown scents they must process and make their peace with before they can feel comfortable. Or as Rudyard Kipling put it, “The first condition to understanding a foreign country is to smell it.”





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