There are lots of good things to smell in the summertime: flowers, steaks on the barbecue, fresh-cut grass. But there are also other, less fortunate smells: hot wet dog, five-day-old roadkill–and skunk.

My personal experience of the smell of skunk has been limited to a whiff of that inimitable scent wafted on the breeze, for which I am grateful. But many a pet owner has had a much more up-close-and-personal encounter with the smell, and this year has been worse than usual, because the skunk population is booming. That’s because there’s also a huge population of mice and voles this year and, although most people don’t realize it, skunks are predators who feed on mice and voles. (Also grasshoppers, crickets, ground squirrels, young rabbits, birds’ eggs, various plants, white grubs, army worms, cutworms, wasps and bees. And we humans like to think WE’RE omniverous!)

There are eight different species of skunks in North America, but only two occur in Canada, and only one, the striped skunk, is widespread. (It also goes by the catchy scientific name Mephitis mephitis. Mephistis is a Latin word meaning “bad odor”–such a bad odor, apparently, that whoever named it used the word twice for emphasis!) The striped skunk is about the size of a cat, with a stout body, a small head, short legs and a bushy tail. Its distinctive black-and-white fur is not particularly conducive to hiding out of sight; that’s because, like the porcupine, the skunk generally doesn’t bother. Running away and hiding are not its primary methods of defense.

Skunks live underground (or under buildings), but they rarely dig their own dens; they prefer to use the abandoned dens of woodchucks, foxes, or other mammals their size or larger. They’ll line one area of their den with leaves to use as a nest. They build a heavy layer of fat in the summer, then spend the winter mostly inactive (though not actually in hibernation) in their dense, emerging in early spring, which is when a young skunk’s fancy turns to love. By early May, the new crop of skunks is being born. Young skunks stay with their mother until autumn, and may spend the next winter with her. Skunks may go out to forage for food at any time of the day, but they’re primarily nocturnal. They usually stay within about a kilometre of their den.

Skunks are members of the weasel family, Mustelidae. All members of this family have well-developed scent glands and a musky odour. The skunk has the best-developed scent glands of them all, though; and what makes it unique is that it uses the liquid it produces in those glands as a defense.

Skunk musk is a thick, yellow oily fluid, secreted by two glands located at the base of the tail. Each gland is about the size of a grape and contains about a tablespoon of musk. That’s enough for about six discharges; if they’re discharged all at once, it takes the skunk up to 10 days to replenish its supply, which is one reason that skunks only use their spray as a last resort: they’ll always try to retreat from a human or other large enemy first. They also give plenty of warning before they spray. An angry skunk will stamp its feet, click its teeth and growl or hiss. The striped skunk will sometimes even walk a short distance on its front feet with its tail high in the air. It can’t spray in that position, but it’s enough to make any person or animal who knows what the skunk is capable of consider beating a rapid retreat. If the skunk is forced to spray, it usually humps it backs and turns in a U-shaped position so that both its head and tail face the enemy.

That’s probably so it can get a better shot away. Skunks can spray up to six metres, and have considerable accuracy up to three. They’ll aim for the face of their attacker if possible, because their spray causes severe smarting of the eyes, quite apart from the smell, which is strong enough to cause nausea. Blind and retching, few animals are interested in pursuing the skunk after being sprayed.

What exactly is in skunk spray that makes it so overpowering? Its primary ingredients are chemicals called thiols–specifically crotyl mercaptan, isopentyl mercaptan, and trans-2-butenyl thioacetate, if you must know. (Many books still list the active ingredient as butyl mercaptan [the substance added to natural gas to give it a distinctive smell] but that’s based on an analysis carried out almost a hundred years ago. The first two chemicals I mentioned are minor variants of butyl mercaptan; the third has so far been identified in nature ONLY in skunk spray.) One of the things that produces thiols in nature is the degradation of proteins. It’s thiols that make decomposing flesh and feces both smell so bad. Almost all animals are naturally repulsed by thiols; that’s a survival trait, because it keeps them from eating things that will make them sick. Skunk spray, then, is essentially distilled disgust–purified putrification–essence of eeeyyeeeeww.

Not only does skunk spray smell strong when first released (strong enough to be smelled even by we poor-nosed humans up to a kilometer away), it also lingers. Dr. William F. Wood, the professor of chemistry at Humbolt State University in Arcata, California, who carried out the analysis of skunk spray I quoted above, found that skunk spray also contained, in addition to thiols, corresponding thioacetates. Thiols are highly volatile and dissipate quickly; thioacetates react slowly with water to form (what else?) thiols. So the smell of skunk can take a very long time to wear off, and washing it off is also difficult because the water keeps activating new scent!

Which, of course, brings up the age-old question, “How do you get rid of skunk smell?” The most popular choice seems to be a bath of tomato juice (though orange juice, vinegar and vanilla extract have also been recommended), which is messy, expensive, turns your dog pink (assuming it’s a dog you’re washing, and not [yuck!] yourself) and, quite frankly, doesn’t work very well. In fact, according to the aforementioned Dr. Wood, it probably doesn’t work at all. He conducted an experiment in which he put two drops of skunk spray into 100 millilitres of tomato juice and mixed for one minute. The mixture smelled strongly of skunk, as you’d imagine–but one minute later, Dr. Wood could only smell skunk. For a moment, it seemed tomato juice really was the magic elixir–but the experiment wasn’t finished. Dr. Wood went for a two-hour walk in the open air, came back–and the mixture smelled strongly of skunk again.

His conclusion is that skunk smell is literally stuns our noses; they suffer olfactory fatigue, and the receptors for skunk odor quickly shut down. Once that happens, the smell of tomato juice is much stronger, and thus people are fooled into thinking it has removed the skunk scent, when it really hasn’t done a thing.

So is there a scientifically proven method for removing skunk smell? Well, most chemists who are part of the chemistry education newsgroup on the Internet recommend a formula developed by a Chicago chemist named Paul Krebaum. Krebaum was conducting research into ways to rid laboratories of foul-smelling thiols, which, as noted, are produced by many other things than skunks. He realized that if you could get oxygen molecules to bond with thiols, they’d turn into other chemicals that didn’t smell bad at all. As it happens, combining hydrogen peroxide and baking soda produces huge amounts of oxygen–and that did the trick. When one of Krebaum’s colleague’s pet cat had a run-in with a skunk, Krebaum suggested using a variation of the mixture he’d used in the lab: and it worked.

His results were later confirmed most dramatically by Tom McCutcheon, a plant pest biologist with the West Virginia Department of Agriculture, who read about the scent-removing formula (which was published in the Chemical and Engineering News in October, 1993), and, being skeptical, decided to try it himself. He picked up a fresh-killed skunk from a local back road, took it back to the lab, dunked it into the solution–and the smell, which was making his eyes watering, went away.

The formula (these are cat-sized amounts; you might have to scale it up to take care of a large dog): one quart of three-percent hydrogen peroxide, 1/4 cup of baking soda and one teaspoon of liquid soap (which breaks up the oils in the spray and lets the other ingredients get at the thiols). Rinse the animal off with tap water.

Much as we try to avoid skunks (not only because of their smell because they can also carry rabies, like any other wild mammal), they are actually very useful. Although they sometimes raid chicken coops and bee hives, it’s estimated that 70 percent of their diet is actually beneficial to humans, and only five percent is harmful to human property. And you have to admire them: they’ve managed to flourish while many other species are declining (skunks are now far more widespread than they were in primeval times) in part due to their incredibly effective defense mechanism.

Should you or your pet be on the receiving end of that mechanism, as you prepare your bath of hydrogen peroxide and baking soda, perhaps it will make you feel better to think of the infinite creativity of Nature, and the wonderful way skunks have adapted to cope with a hostile world.

Then again, maybe it won’t.

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