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A Sign of Spring in the Air

     Punxsutawney Phil may have recently seen his own shadow (as well as those of many reporters), but my own family's personal indicator that spring is somewhere around the corner arrived a few days before Phil was making news. The excited barking of our dogs woke us shortly before the alarm went off and a musty, putrid smell greeted our noses. The stench intensified as we walked down the hall and a look out the living room window confirmed our fears. Right below the window, next to the front door, trapped in the corner where the fence meets the house, separated from us by only two panes of glass (with apparently poor seals), sat Mephitus mephitus, the striped skunk. The dogs were alternating between rubbing their faces on the ground and moving in on the skunk. When they were too close for comfort (the skunk's and our own), Mr. Mephitus let go with another well-aimed blast. In less than an hour, the school bus would arrive to pick up our kids and the daycare moms would be dropping off theirs. Life is seldom dull.

      I slipped into an old pair of coveralls, draped an old shirt over my head, and armed with everything but a plan, went outside to try to get the dogs away from the skunk. Mr. Mephitus was actually somewhat helpful at this point, nailing our female weimaraner on the nose sending her running my way. After locking the dogs in an old shed,  I approached the skunk with a bucket of water hoping a quick dowsing would scare him away from the front porch. The skunk sensed my presence, though, and dug his head further into the corner, pointing his business end my way. We quickly agreed on a compromise:  I would go back in the house and he could leave whenever he felt like it.

      If every cloud has a silver lining (and there was no doubt a cloud!), this one's was that the daycare kids (after entering through the back door) were thrilled to watch a skunk only a few feet away protected from direct spray by a window. The entertainment lasted through mid-morning, when the daylight-shy Mr. Mephitus finally ambled away.

      Striped skunks are not true hibernators so spotting a skunk in late winter is probably no more accurate an indicator of the nearness of spring than whether Punxsutawney Phil sees his shadow. Still, skunks in our area do sleep for extended periods of time during the extreme cold of our winters and become more active as spring approaches. As interesting as skunks may be, though, this essay is not devoted to the natural history of, pound for pound, the most respected mammal anywhere. Nor is it about the accuracy of Punxsutawney Phil's weather forecast (he's right about half the time). Instead, our visit from Mr. Mephitus got me thinking about the least understood of our five senses--the sense of smell.

 The Underrated Sense

      If we had to give up one sense, most of us would probably choose the sense of smell. Yet no other stimuli (sounds, sights, textures) can affect us to the degree that odors can. A particular odor can instantly trigger a vivid memory of a person, place, or event. Offensive odors can make us nauseous while pleasant odors can heighten our mood. Most foods would taste fairly bland if we weren't able to smell the foods we were eating. Even so, movie theater popcorn never tastes as good as it smells; and sauerkraut, so I'm told, never tastes as bad as it smells. Odors are the foundation of many businesses which capitalize on the idea that people would love to eliminate odors we find offensive and surround ourselves with odors we find appealing. The sense of smell doesn't get much credit for the important role it plays in our lives .

      The oldest sense of all, smell originally developed when all life forms were still confined to water. The ability to detect and recognize from a distance molecules given off by food sources, potential mates, or possible danger increased a living thing's chance for survival. Most animals today still rely heavily on the sense of smell. Dogs, bears, and the majority of mammals "see" the world through their noses. Birds (with the exception of turkey vultures) are the only vertebrate animals without a developed sense of smell, which explains why the great horned owl is the skunk's greatest predator. 

What is Smell?

      Much of smell is still a mystery but we do know that smell involves the detection and recognition of certain molecules diffused in the air. The region in our nasal passages responsible for odor detection is made up of two small grooves with a surface area about the size of a quarter. This olfactory area is made up of special structures that are in some way sensitive to airborne molecules in the nasal passages. Nerve fibers lead from these structures to the olfactory bulb at the forward base of the brain, where the smells are interpreted. 

How the Nose Knows

      The current model for how odors are detected can perhaps be best described with a lock and key analogy. There appear to be seven primary odors--ether-like, camphor-like, musky, floral, minty, pungent, and putrid. Our olfactory area has, according to this model, seven different kinds of receptors, each like a lock with its own specific key. A molecule from a substance giving off a primary odor is unique in some way (size, shape, or electrical charge, for example) so that, like a key, it only "fits" its specific receptor. The strength of an odor would be determined by the relative number of receptors filled at one time. There are of course, more than seven specific odors we can detect, but each odor could be explained as result of giving off a unique combination of molecules that fill a variety of receptors at the same time. 

Still More to Learn

      While this model (dubbed the "stereochemical theory of odor") has held up well to experimental testing, there is much about the sense of smell we do not yet understand. Sometimes, the agreeableness of a smell depends on its concentration. For example, when exposed to small concentrations of skunk odor (ethyl mercaptan), most people describe the odor as pleasant if they are not first told its source. Also, people differ in their ability to detect odors and in how they react to them. Some people suffer from a kind of "odor-blindness" and are not able to detect certain smells; a lucky one in a thousand cannot detect skunk odor at all. Additionally, not everyone agrees on which smells are offensive. Some people find even high concentrations of skunk spray pleasant! Finally, we seem to lose our awareness of odors to which we are continually exposed. Our homes, cars, and personal belongings all have characteristic odors that we don't notice but other people do. There are still many mysteries about smell to be solved.

      Spring will come and bring with it a flood of odors, many pleasant, some not so appealing, but all telling us something about what is happening around us. Each of us has personal signs we look for as our own indicator of spring's arrival--perhaps the thawing of a favorite fishing lake, the first green leaf to break through the barren ground, or the sounds of sandhill cranes. Should an animal make an appearance at your doorstep to announce spring's arrival this year, though, I hope it is Punxsutawney Phil's cousin, the marmot, searching for his shadow.  Mr. Mephitus is a truly handsome creature, but he may come bearing a fragrant gift that cannot be returned.

2006  Dirk Oden

 

 

   
 

 

This site was last updated 09/05/06