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The Chemistry of Skunk Spray

Posted: October 13, 2016

Why do skunks smell so bad? It all comes down to chemistry.

By the way, this video will include slow motion footage of skunk anuses. So, be warned.

I’m Anna Rothschild, and this is Gross Science.

There are a number of species of skunk in the world, but the most iconic has to be the striped skunk. That’s the one that looks like Pepe Le Pew—it’s all black, typically with one white line that usually splits into two on its back. And it can be found all over the United States as well as northern Mexico and southern Canada. Its latin name is Mephitis mephitis, which appropriately enough means something like foul stench or noxious vapor.

Obviously, that’s because the most defining character of skunks is their defensive spray, which can cause watery eyes, nausea, and leave you smelling terrible. The chemical makeup of the spray is different depending on the species, but all of them contain special types of compounds called “thiols.” Thiols, also known as “mercaptans,” are a type of chemical group made up of a sulfur and hydrogen atom bonded together. And they typically smell really strongly.

There are actually three different thiols in striped skunks spray, and two of those are the main contributors to the awful odor. But three other molecules in the spray are what are called “thioacetates.” Those compounds don’t have a strong scent, but they can easily become thiols when they’re exposed to water. And that might explain why a pet that gets sprayed may start to smell skunky again after a bath.

Now, skunk musk is produced by anal scent glands—which actually, lots of mammals have, though most aren’t quite this exciting. When a skunk sprays, nipple-like protrusions called papillae come out of the anus and squirt the musk at the target. The bad news is they can squirt a distance of about 10 feet, and are uncannily good at hitting their mark. The good news is that skunks really don’t want to spray unless they have to, and adults usually give warning signals beforehand. Striped skunks will hiss, stomp, and raise their tails before spraying. And spotted skunks will even do a handstand.

But, what should you do on the off-chance that you wind up covered in musk? Well, definitely don’t use tomato juice—that’s just a myth. Instead, use something that converts the thiol into a different type of compound. Some scientists suggest using a mixture of dilute hydrogen peroxide, baking soda, and a little liquid soap, which will oxidize the thiol and turn it into a sulfonic acid. But be careful, because it could dye your hair or pet fur.

Anyway, despite their terrible reputation, some skunks have actually been domesticated, and people say they make really cute and affectionate pets. But if you do want a pet skunk, make sure you know how to take care of it and get one from a breeder. Grabbing one from the woods is not at all nice for the skunk. And it would probably let you know that by squirting you with an anal gland full of noxious musk.

Ew.

PRODUCTION CREDITS

Host, Producer, Editor: Anna Rothschild
Researcher, Writer: Eliza Lehner
Camera, Sound: Gil Kaplan; Many thanks to Drs. William F. Wood and Stanley D. Gehrt
Comme Un Pigeon: Music Provided by APM

FOOTAGE AND IMAGES

Footage of Skunk Spraying: Courtesy WNET
NATURE “Is That Skunk?”
Stinktier, Skunks, Mephitis mephitis, Striped Skunks, Minnesota, USA, cub: Shutterstock/Bildagentur Zoonar GmbH
Blue Merle Australian Shepherd puppy, 10 weeks old, looking at Striped Skunk, Mephitis Mephitis, 5 years old, sitting in front of white background: Shutterstock/Eric Isselee
Pepe Le Pew Gif: Giphy/Warner Brothers
Baby skunk: Wikimedia Commons/AnimalPhotos
Juvenile Spotted Skunk: Flickr/vladeb
American hog-nosed skunk (Conepatus leauconotus): Flickr/Saguaro National Park
Striped Skunk: Flickr/Land Between the Lakes …
Striped Skunk (cropped): Wikimedia Commons/ http://www.birdphotos.com
Striped Skunk: Wikimedia Commons/ http://www.birdphotos.com
Washing a dog in a bath tub: Wikimedia Commons/Andrew Vargas
Mephitis: Flickr/Jon Nelson
Spotted Skunk and Cocomistle: Flickr/Ryan Somma
Tomato juice 316744: Wikimedia Commons/PublicDomainPictures-14
Skunk being cuddled: Wikimedia Commons/Gary J. Wood
PET SKUNK: Wikimedia Commons/Paul M. Walsh
Lapskunk: Wikimedia Commons/octobop
Baby Striped Skunk: Flickr/Land Between the Lakes …