Ask Smithsonian: What Makes Skunk Spray Smell So Terrible?

When the omnivorous cat-size mammals take aim, the malodorous spray can hit with pin-point accuracy up to 20 feet away

The scent of a skunk is legendary and lingering, but not in a good way.

As powerful as it is, however, the spray is a closely-guarded weapon of mass destruction, says Kenton Kerns, a biologist at the Small Mammal House of the Smithsonian’s National Zoo in Washington, D.C.. It is never used in skunk-on-skunk fights over territory, only for predators that don’t get the message—and then, sparingly.

That’s because even a single spray could almost completely deplete the liquid, which is produced in the skunk’s anal glands, says Kerns. “It’s constantly being made, but it’s a slow process,” he says, adding that it could take up to 10 days to refill the glands, during which time the skunk would be highly vulnerable to predators like wolves, badgers, coyotes and great horned owls.

The omnivorous cat-sized mammals roam a large swath of North America, foraging for insects—their favorite food—and scarfing up mice and all kinds of plants. Their distinctive black and white coloring is theoretically the first warning that they should not be trifled with, says Kerns.

But some animals, dogs, in particular—since they’ve lost a lot of their innate knowledge of the natural world—don’t seem to notice, and venture too close. The skunk may stamp its feet. If that doesn’t get a reaction, it will likely raise its tail, and those who’ve had previous encounters know what comes next. Via two nipple-like independently-rotating squirters that flank the anus, the skunk will take aim and fire away.

“They have a pretty decent aim, apparently,” says Kerns, noting that he’s seen reports that the spray can hit with accuracy as far as 20 feet away, but that 10 feet is the accepted range.

The skunk wants to control accuracy and distance so as to not waste the precious liquid, he says. Usually, a very small squirt is released—enough to make a predator, or a curious human, or a dog, or a cat, “stop, and turn around and run away,” says Kerns.

It doesn’t take much to have an impact. Skunk spray is a thiol, an organic compound with sulfur as a principal component. Sulfur has that classic rotten egg smell, and it’s what gives thiol its gag-inducing power. For detection purposes, thiols are added to otherwise smell-free natural gas, so that it will have a noticeable odor. In the case of skunk spray, the thiol is so potent that it can be smelled a half-mile away, says Kerns.

Generally, the spray doesn’t cause much harm—maybe stinging in the eyes or temporary blindness, and nausea in humans—but it can definitely linger on fur or on a roadway, long after the skunk has made its escape or taken its last walkabout. 

And it’s effective.

“Usually, if you have one altercation with a skunk, you remember that the rest of your life,” says Kerns.

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