Why Skunks Evolved Their Smelly Spray

Skunk spray is so potent that it can knock you out or even kill you—and now we know why the North American mammals evolved the noxious stuff.

Skunks are nocturnal, and their predators rely heavily on scent to navigate in the dark. But skunks evolved a counterattack: Their foul and damaging spray foils would-be attackers, according to Ted Stankowich, co-author of a new study on the subject in the International Journal of Organic Evolution.

Shawn Geary holds a skunk during Skunkfest, held annually in North Ridgeville, Ohio. Photograph by Vincent J. Musi

“Mammals use scent a lot in their daily lives, so being able to spray a predator with something that’s truly awful would knock them out,” said Stankowich, an animal behaviorist at the University of California, Long Beach. “When dogs get sprayed, they might get chemical burns.”

For the study, Stankowich and colleagues did an extensive study of 181 species in the order Carnivora, of which the skunk is a member, and compared them to see how predation and other variables influenced the evolution of “noxious weaponry” like spraying.

This form of defense is a type of chemical weapon found often in nature. In skunks, the oily spray is stored in a skunk’s anal sacs and can shoot out of their butts up to ten feet (three meters) away. (Also see “Why Skunks Have Stripes: To Point to Fierce Anal Glands?)

All carnivores have these anal glands, but not all of them stink, said the University of New Mexico’s Jerry Dragoo, a biologist who was not affiliated with the study. For example, beaver secretions smell like vanilla and are used to mark territory.

But skunk spray includes chemicals called thiols, sulfur-containing compounds that help give the liquid its awful stench. Thiols are also used in anesthetics and antispasmodics, which is why they have such a profound physical effect on potential predators.

One Tough Mammal

Dragoo noted that skunk musk is a highly effective means of avoiding physical confrontation and buying extra time to get away from hungry predators.

“If a big animal is coming after you, and you can spray a noxious chemical at it, they usually stop chasing you,” Dragoo said. “The skunk can defend itself.” (Watch a skunk video.)

But skunks—to their credit—generally use spraying as a last resort, flashing their black-and-white colors, doing a little dance, and thumping the ground as a first warning.

They’re also scrappy, with teeth and claws they’re not afraid to use.

And it seems to work: Stankowich noted that skunks rarely die from being killed by predators.

Rosy Skunks? 

High concentrations of skunk spray are toxic and potentially fatal to humans, according to a 1999 study in Chemical EducatorThe powerful stuff has been likened to tear gas because it can cause temporary blindness, coughing, and gagging. 

But not for Dragoo, one of the few scientists willing to study the Pepe Le Pews of the animal kingdom. When Dragoo first started surveying the woodland creatures, he was surprised to find that he wasn’t affected by their odoriferous excretions—turns out, he’s one of the few that cannot smell skunk musk.

“The first skunk that sprayed me, I wasn’t sure what happened,” he said. “I looked at the animal, and he looked back at me, and there were yellow spots all over me. I couldn’t understand why people were making such a fuss.”

After three days in the field, Dragoo returned to work unknowingly smelling to high heaven, and “they wouldn’t let me back in the building.”

“People complain that their eyes are burning; they’re gagging and wheezing,” he said. “They have to leave.”

“Skunk spray all smells like rose petals to me!”

Follow Mollie Bloudoff-Indelicato on Twitter.

Mollie Bloudoff-Indelicato is a science journalist who loves em dashes, ’80s music and parasites. She has a master’s degree from the Columbia University Graduate School of Journalism with concentrations in science journalism, photography, and radio reporting. Contact her at news@mbloudoff.com, and follow her on Twitter at @mbloudoff.
  • Ima Ryma

    As a skunk, I’m bummed to find out
    Some human dude thinks that my scent
    Is rose petalled – what’s that about!
    Not a smell I want to present
    For unwanted confrontation.
    Yes, spraying is a last resort,
    Some flashing, some thumping’s first done,
    Scrappy with teeth and claws to thwart,
    But it’s just knowing I’m butt armed
    To shoot noxious up nosy nose,
    As my main means from getting harmed.
    Now I find out I’m shooting rose!

    How would a Valentine’s Day be
    Getting a big bouquet of me?

  • Jim Bendewald

    I am starting to create a list of instances of “evolution of the gaps”. We don’t know how skunks obtained their effective “noxious weaponry” but evolution must have done it.

    My favorite is example of “evolution of the gaps” is Junk DNA. For dozens of years scientists did not know what the function of the 98.5% of the human genome was for. Evolution is the only acceptable paradigm for Richard Dawkins and other atheists. So it was popularized that 98.5% of the human genome is the remnants of millions of years of evolution. It is a wonderful example of “evolution of the gaps”.

    But with ENCODE we see that Junk DNA is not junk any longer. How long will it be before the general public comes to have the wool removed from their eyes to see that the “just so” stories of evolution are just stories?

  • Larry Masters

    The evolution of skunk spray indeed! A defense mechanism…yes, but evolution is so slow isn’t it, but me and my skunk cousins throughout history had to accidentally mutate just the right spray substance to run off our attackers. First, after millions years, we evolved the creation of a mucus spray. Oops that didn’t work. Then after more millions of years it was perfume (Chanel No. 5 I do believe). Nope that ain’t working either. Then lemon juice, Windex, Lipton Tea, Coca Cola…oh my, all these don’t fend off any predators and we’re wasting millions of years aren’t we. Finally we stumble upon that famous foul musk spray. Bingo!, now we skunks can protect ourselves!…but wait, why protect myself? What gives me the notion of self preservation? …or to protect my young?…or to reproduce at all? Who cares? I just wanna eat supper. Oh but why should I want to eat? Who cares? Oh yeah, evolution told me to do all that. Thanks Evo! U da man!

  • Kenny Merriken

    This article says “… Stankowich noted that skunks rarely die from being killed by predators.” But they do have a predator that is not bothered by the smell. The National Geographic article on the Great Horned Owl says, “They regularly eat skunks, and may be the only animal with such an appetite.”
    Skunks are a beautiful example of God’s creation (Genesis 1:24-25). Their defensive mechanism makes a lot of “scents”. The first skunk family had to have this defense already built into their system otherwise the would be eaten by many predators and become extinct very quickly.

  • Patrick Dennis

    National Geographic should really edit idiot creationists comments. See Kenny’s comment above about the first skunk family needing to have this defense built in?
    Well, the thing is, there was no 1st skunk family. This is alluded to in the article which mentions that skunks are multiple species within the order Carnivora (Class Mammalia) (What species of skunk was the first skunk family anyway? Did that one initial species diversify into all known species? Sounds like evolution). More to the point skunks share various common ancestors with other carnivoran mammals (Canidae, Felidae, bears etc). So skunk spray isnt a shared trait. It is a derived trait if skunks.

  • Patrick Dennis

    Larry Masters just doesnt get it either. He seems to think skunks were already skunks while they were working on the last little trait that would make the truly skunks. That’s not how natural selection works..

  • Patrick Dennis

    Jim Bendewald is hudlffing and puffing about junk DNA. (It exists).but I’d like to address his “evolution of the gaps” comment.
    As far as skunk evolution goes we know that skunks are mammals, mammals are amniotes, amniotes are tetrapods (along with various types of amphibians), and all tetrapods are essentiallly lobe-finned fish. This is a non controversy in paleontology. It is also born out by the molecular ohylogeny of tetrapods (All 4-limbed animals are more closely related by way of shared DNA mutations to lungfish than they are to other lobe finned fish such as the coelocanth) So we can safely conclude skunks are evolved from lobe-finned fish..Given this kind of indisputable evolutionary relationship for every other trait that skunks posses (vertebrae, four-limbs, fur etc) why should scent glands be any diffetent.

  • Kate

    I came to this article because I smelled skunk spray in the neighborhood and got really sick. I’m auto-immune. Reading the article, and the comments on it about evolution, was singularly un-helpful. I do agree that it’s unlikely that a skunk would randomly evolve something that another similar creature would not have: the theory of evolution does not answer its own question: why is there more than one species? Why, if we evolved from the same creature, do we not share enough DNA to mate? If sexual reproduction is our greatest means of moving forward, why can’t a human procreate with a dog to have young with better hearing. It’s pretty obvious that evolution and adaptation are two different things and atheists cling to pseudo-science. As per Einstein: insanity is doing the same thing over and over and expecting a different outcome. The more scientists have attempted to disprove the events in the Bible, the more they have proven.

  • Tony Vargas

    Patrick Dennis, your comments makes no sense you are so sure that skunks evolved from a lung fish, however that’s just the product of your imagination because the fossils do not show change,all fossil ever found were of complete animals never has a fossil been found of an animal in the changing stage, therefore it is theory not a fact.

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