|
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. |
