Oregon State University study sheds light on elusive western spotted skunk

Marie Tosa, a postdoctoral researcher in the Department of Botany and Plant Pathology at Oregon State University, spent two and a half years trapping and tracking the movements of western spotted skunks across thousands of acres in forests in the western Cascades, roughly 60 miles east of Eugene.

Little is known about the small, nocturnal carnivores, which weigh between one and two pounds and burrow inside logs and hollows to avoid predators like bobcats and owls. Tosa’s field work unearthed new information about the behavior of these skunks, including a home range of up to 12 square miles they can cover while hunting for food. She also found that western spotted skunks may be vulnerable to extreme winters, which are becoming more frequent due to climate change, and the importance of old growth forests for their habitat. Tosa joins us to share more of her findings and remaining questions about the skunks' resilience to climate change.

Note: The following transcript was transcribed digitally and validated for accuracy, readability and formatting by an OPB volunteer.

Dave Miller: From the Gert Boyle studio at OPB, this is Think Out Loud. I’m Dave Miller. My next guest spent two-and-a-half years trapping and tracking the movements of western spotted skunks across thousands of forested acres in the western Cascades. Marie Tosa is a postdoctoral researcher in the Department of Botany and Plant Pathology at Oregon State University. She set out to find more information about these 1 to 2 pound nocturnal carnivores. And she learned a lot, including the fact that they can range over 12 square miles – a much bigger area than deer, which are about 100 times bigger. Marie Tosa, welcome to Think Out Loud.

Marie Tosa: Hi, Dave. Thanks for having me.

Miller: Thanks for joining us. So I assume that many or maybe most of the folks who can hear now, including me, have never seen [spotted] skunks. I actually never even heard of them before I saw a press release about your study. So, what is a western spotted skunk?

Tosa: A western spotted skunk is kind of the smaller cousin of the striped skunk that you probably have seen in your neighborhood at night. That’s the one that you probably have your dog get sprayed by when it goes out at night, and you get that really strong stench. But the western spotted skunk is only about 1 to 2 pounds. It’s about a fifth of the size of the striped skunk. And it lives in the forest, especially in the western Cascades, and also in the coast range in Oregon.

Miller: Why did you want to study this particular species?

Tosa: I get that question a lot. I would say not many people set out to become skunk biologists, and I certainly also was not one of those people. But when I learned about the spotted skunk, and just how abundant they are in our forest, the fact that we just don’t know very much about them made me want to study them and just learn what are they doing out there. They’re one of the most abundant carnivores in our forests, but we just have no idea what they’re doing. What are they eating? How far are they moving? We just have so many questions about them.

Miller: My understanding is that one of your motivations was that there is an eastern cousin of this skunk, and their population went down dramatically in the middle of the 20th century. So what happened with these other skunks on the other side of the country?

Tosa: We really don’t have any idea. We have some hypotheses about what happened to these eastern spotted skunks. They’re now called the plain spotted skunk. But yeah, we just don’t really have any of that data in terms of what caused the decline. Some people think that it’s due to disease. Some people think it’s due to pesticides that are used in agriculture. Another one is there’s just habitat loss for these eastern species. But because we weren’t studying them, because they were so abundant at the time, we didn’t really care about them, we weren’t keeping tabs on them. And then in about 10 years, their populations declined by 90%. And over 40 years, they declined by 99%. So all of a sudden we were kind of in this situation where we were like, oh, no, what do we do? The species is declining really rapidly, but we don’t know how to save it.

Miller: And is part of the idea to learn more about the western varietal the fear that the same precipitous decline could happen to these ones?

Tosa: Yeah, absolutely. These western spotted skunks we think are very abundant in our ecosystems. But again, if nobody’s keeping tabs on those species, they could also suffer the same fate as the eastern cousin. We have some preliminary information that the western spotted skunks are also declining, but maybe not as quickly as the eastern ones are. Really, it’s a question of do we study them now when they’re really abundant and when we can get really good information on them? Or do we wait until those populations have really tanked already and we can’t really study them that much anymore?

Miller: You mentioned that these skunks in Oregon exist in the western Cascades and also in the coast range. But they have a much wider geographical area, right?

Tosa: Oh, yeah, definitely. So these western spotted skunks seem to be really generalist carnivores. They can be found all the way up in B.C. in Canada. And they can also be found all the way down in Mexico, in the Baja Peninsula, and also in New Mexico and Arizona. So if you think about the variety in terms of the habitat that they can use, it’s really variable.

Miller: So they’re adaptable?

Tosa: Yes, absolutely.

Miller: What would it take for an Oregonian to see one of these in the wild?

Tosa: Yeah, it’s really hard to see them. They’re super nocturnal. So even when I was researching them, I really only got to see them when they were in the trap, or if we had a radio collar on them and we would track them to a specific location, a specific tree.

The best way to see a western spotted skunk is to set up a camera trap, and you might get one of those spotted skunks going by your camera trap at night.

Miller: Let’s turn to your study. First of all, what were the goals of it? What did you most want to learn?

Tosa: The goals of my research were to understand the spotted skunk as much as possible. Since nobody had really studied these westerns spotted skunks before, we just wanted to collect as much information as possible. The three key studies that we were doing were on the diet of the western spotted skunk – what are they eating? The next thing was how much do they move, and what kind of space do they need, what kind of habitat do they need? And the third thing was, what predation pressures do they suffer – what eats the western spotted skunk, what is actually attacking it, what does it need to be afraid of?

Miller: So what do they eat, where do they go and what eats them. How did you collect your data?

Tosa: We first started out by putting out camera traps. These are your everyday camera traps that you would use for hunting. We put cans of sardines on trees so we could bring the spotted skunks into the view shed of the camera.

Next, we would look at those camera photos and see where the spotted skunks were most. And then we put out traps. We put out these box traps, live traps. And that allowed us to put radio collars on these little carnivores ...

Miller: Meaning, you had to actually go to the trap, open it up, and then you were the one putting a radio collar on the skunks?

Tosa: Oh yeah, yup.

Miller: What does that process entail?

Tosa: It’s really exciting. Going up to the trap, you can actually tell that there’s a spotted skunk in the trap, because these spotted skunks will pull in vegetation from their surroundings and make a little nest inside of these box traps. They like to be really cozy, they like to be warm. You can tell right away that something is in there and it’s probably a spotted skunk.

Once you see that the spotted skunk is in there, you’re obviously handling the animal in order to put a radio collar on, so you’re kind of in this danger zone of you might get sprayed, might get sprayed multiple times. In order to try to reduce that, we would try to chemically immobilize them, tranquilize them. But inevitably, we got sprayed every single time that we did that.

Miller: How many times do you think you’ve been sprayed?

Tosa: [Laughter] Probably 50 to 100 times. I just got sprayed by a striped skunk because of my dog the other day.

Miller: Good! Sorry [Laughter]… What I mean is that’s helpful for you to answer this next question, which is is there a difference between the smells?

Tosa: Oh, yeah, I think so. I think that the western spotted skunk has a much more pleasant spray. It smells more like garlic.

Miller: You just love these animals. Can we take this with a grain of salt?

Tosa: You probably should, yeah.

Miller: So more like garlic, the spotted ones, as opposed to … maybe I don’t need to describe the standard skunk smell since probably most of our listeners know.

Do you have any suggestions while we’re talking about this – before we move on to more important ecological questions – of how to best get rid of the smell of skunk? Something I imagine you had to do, even if you like the smell of garlic you probably had to do it 50 to 100 times.

Tosa: Yeah, absolutely. The office people that I was working near did not like the fact that we were getting sprayed constantly. We were using a mixture of hydrogen peroxide, baking soda and dish soap. Just making a paste out of that and just kind of covering whatever parts that we thought smelled the worst.

Miller: Let’s turn to the actual purpose of this. So what do they eat, first of all? And second of all, what eats them?

Tosa: Spotted skunks are eating things that we don’t actually like that much in the forest – yellow jackets and wasps. They seem to be eating a lot of those during the summer. And then in the fall and the winter, they seem to be eating more small mammals, things like flying squirrels, chipmunks and shrews. But they also eat things like black-tailed deer, which was really surprising to us.

Miller: Skunks that are one pound eat deer?

Tosa: They sure do.

Miller: The way of a vulture would, they just find a dead deer?

Tosa: Mhm, yeah. What we think is happening is that they’re scavenging these carcasses that cougars or other larger carnivores are killing.

Miller: I got to go back to the yellow jacket thing. We’ve had a week of political shows for obviously important reasons, but it’s a nice reminder of just how wondrous the world is that there’s a skunk out there, sleeping right now, that’s going to wake up, maybe only in the summer. And then it’s gonna go and what, find a yellow jacket nest, stick its little face inside and eat the sleeping yellow jackets? What is it doing?

Tosa: It’s eating whatever it can find, I think. I think these yellow jackets are really high in protein, and they’re just really delicious. They’re little spicy Cheetos for them.

Miller: What eats these skunks?

Tosa: Yeah, so this is one of the things that we were really interested in. As a lot of you know, the barred owl has come down into the Oregon Cascades. We hear about that a lot with spotted owls, but we found that the spotted skunks are actually being killed by barred owls also. So there’s more than just one owl versus another owl. That kind of effect is having more effects on the ecosystem as a whole.

Miller: And how would you know that a skunk with one of your radio collars was eaten by a barred owl?

Tosa: Yeah, this is actually one of the most exciting parts of doing field work. We can track those collars with a radio, kind of like what you have in your car. It gets louder when you get closer to that signal. And so we can follow that signal to that collar. And it also has this mortality signal. So when it doesn’t move for over eight hours, it emits a different signal than when the animal is moving. We followed this mortality signal to this area, and we actually couldn’t find that collar even though we were traversing that landscape really thoroughly. We even had some detection dogs come out and try to find that radio collar, that skunk. Turns out that radio collar was at the top of a snag. So we enlisted some tree climbers and we got to climb that snag and find that radio collar sitting on top of it, without any other evidence of the carcass.

After that, the detection dogs were actually able to find some of the intestines of the skunk. These dogs are trained to find carcasses and scat. And so they were able to find this intestine pile. And we used DNA to actually figure out what kind of DNA was on there. Obviously, western spotted skunk came back. But also barred owl came back as well.

Miller: So if you combine all of this with that big finding I mentioned earlier, the really seemingly surprising range that these have – 12 square miles, way more than deer as I mentioned – when you combine all this, what does it suggest about the pressures on these seemingly adaptable carnivores? And any concerns you have about say forest management or other human practices in terms of skunk population?

Tosa: One of the reasons that we did this study on what kind of habitat the western spotted skunks need is because we were concerned about the disturbance of logging pressures on the western spotted skunk populations. Because these animals have these really large home ranges, you might think that they would be negatively impacted by logging operations. Where we were doing our study, it was on federal land. And so the amount of logging pressures is fairly low compared to industrial lands, but there is still timber harvest occurring there. So we were wondering, does this disturbance negatively impact the populations?

What we were finding is that the western spotted skunks actually do use those timber harvest areas. Maybe a little bit less than they would the old growth areas, but they are going in there and finding resources. They’re using some of those stumps and logs that are left behind to rest in during the day.

Miller: Marie Tosa, thanks so much for joining us. It was a pleasure talking with you.

Tosa: Thanks so much for having me.

Miller: Marie Tosa is a postdoctoral researcher at Oregon State University. She spent two-and-a-half years tracking and trapping western spotted skunks, which are small nocturnal forest carnivores.

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