If you see a skunk doing a handstand, as remarkable as the sight may be, you should probably step back. A few good steps back. It’s the last warning before they start spraying with their famous putrid-smelling liquid.
Not all skunks do handstands, just the spotted ones. The most common skunk in North America is the striped skunk — a stocky animal, around the size of a housecat, black with white stripes; think Pepé Le Pew. The spotted, hand-standing skunk is smaller, at under one kg (two pounds), and a bit more mysterious than its striped cousin.
Researchers even debated how many species of spotted skunk there are, with the number ranging from two to fourteen, and later settling in on four. But according to a new study on skunk DNA, there are actually seven species.
The acrobats of the skunk world
The Wikipedia page of the spotted skunk (and pretty much all the sources you can find) lists four extant species of spotted skunk: S. gracilis, S. putorius, S. pygmaea, and S. angustifrons — with the “S.” standing for the Spilogale genus of the spotted skunk.
But a team of researchers has a different idea on these species, and they have the DNA to back it up.
“I was able to extract DNA from century-old museum samples and it was really exciting to see who those individuals were related to. It turns out that one of those was a currently unrecognized, endemic species in the Yucatan,” says Molly McDonough, a biology professor at Chicago State University, research associate at the Field Museum, and the paper’s first author.
It’s striking that even for such a well-known animal as the skunk, on a relatively well-explored continent, we can still find out new things, and re-align the species’ tree of life.
“North America is one of the most-studied continents in terms of mammals, and carnivores are one of the most-studied groups,” says Adam Ferguson, one of the paper’s authors and the Negaunee collections manager of mammals at Chicago’s Field Museum. “Everyone thinks we know everything about mammalian carnivore systematics, so being able to redraw the skunk family tree is very exciting.”
Skunks are distantly related to dogs, and despite being part of the Carnivora order, they’re omnivores (capable of eating both plants and other animals). Striped skunks are more familiar to most people in North America because they’ve made their way to some urban and suburban areas. They’re also larger than the spotted ones, which tend to be smaller and enjoy staying out of sight when they can.
All skunks can spread a fetid liquid, but the smaller spotted skunks have the more spectacular display: they do a hand-stand on their front legs.
“Spotted skunks are sometimes called the acrobats of the skunk world,” says Ferguson.
Ferguson, McDonough, and colleagues analyzed DNA samples both from wild specimens and museum specimens, finding that some skunks that were once thought to be the same species were actually very different; sometimes, genetic differences don’t translate to visual differences.
Based on these genetic differences, they were able to regroup the spotted skunk group. In the process, they ended up bringing back species names that haven’t been used in centuries.
Important for conservation
The diversification of spotted skunk species appears to have started relatively recently.
“By analyzing the genome of spotted skunks, we’ve been able to learn that their evolution and splitting into different species was driven by climate change during the Ice Age,” says Ferguson.
However, knowing what species a group has is important not just for building an evolutionary tree, but also for knowing which species are threatened by extinction. For instance, if what we thought was one species turns out to be two species, and one of them is doing just fine and the other is not, we could tailor conservation efforts to protect the endangered one.
This is also the case for some new species emerging from this study. For instance, the Plains spotted skunk has been known to be in decline for the past century. But conservationists thought this was a subspecies, not a full-fledged species.
“If a subspecies is in trouble, there’s sometimes less emphasis on protecting it because it’s not as distinct an evolutionary lineage as a species,” says Ferguson. “We’ve shown that the Plains spotted skunks are distinct at the species level, which means they’ve been evolving independently of the other skunks for a long time. Once something has a species name, it’s easier to conserve and protect.”
The study also offers a new opportunity for researchers to understand spotted skunks. Handstands aren’t the only unusual thing about them, researchers say.
“Besides the fact that they do handstands, the coolest thing about spotted skunks is that some of them practice delayed egg implantation—they breed in the fall, but they don’t give birth until the spring. They delay implanting the egg in the uterus, it just sits in suspension for a while,” says Ferguson. “We want to know why some species have delayed implantation and others don’t, and figuring out how these different species of skunks evolved can help us do that.”
Journal Reference: Phylogenomic systematics of the spotted skunks (Carnivora, Mephitidae, Spilogale): Additional species diversity and Pleistocene climate change as a major driver of diversification, Molecular Phylogenetics and Evolution, 2021.