Short Wave - When Tiny, Invasive Ants Go Marching In...And Alter An Ecosystem

Episode Date: January 26, 2024

At the Ol Pejeta Conservancy, a wildlife preserve in central Kenya, lions and cheetahs mingle with zebras and elephants across many miles of savannah – grasslands with "whistling thorn" acacia trees dotting the landscape here and there. Twenty years ago, the savanna was littered with them. Then came invasive big-headed ants that killed native ants — and left the acacia trees vulnerable. Over time, elephants have knocked down many of the trees. That has altered the landscape — and the diets of other animals in the local food web.Curious about other science news? Email us at [e-mail]. See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Hey, short wavers, Regina Barber here. And this time I've got two of our favorites for our regular roundup of science news. Wana Summers. Hey, Wana. Hello, thank you for letting me hang out again. And science correspondent Ping Huang. Hey, Ping.

Hey, Regina. Hey, Wana. Hi. As always, we're going to share three science stories in the news that have caught our attention recently. Number one, how a bunch of tiny invasive ants have changed how elephants act and what lines. eat. What a sample of ancient chewing gum tells us about dental care and diets in the Stone Age? And then billions of cicadas appearing this spring. All that on this episode of Shortwave, the science podcast from NPR. All right, Wana, you're the guest. Which topic do you

want to start with? Oof, hard to pick. I'm kind of into all of these, but I don't know, let's start with the ants. Okay, so this story starts in the Savannah at a nature preserve in central Kenya. And Juana, if we went back 20 years, we would see grasslands that are covered with acacia trees. And these trees provide food and shelter for native ants. And in turn, the ants defended the trees against animals that would eat the trees, like elephants. Like when elephants would grab tree leaves, the native ants would swarm up inside their trunks and bite them. This does not sound fun. No, no, not at all.

And for a long time, the trees and the ants had this like mutualistic relationship. And then about like 20 years ago, this new, invasive ant showed up. It's called a big-headed ant, and it starts taking over the territory, killing the native ants, and leaving these trees undefended. Okay, I think I know how the story goes. Let me guess here. The elephants are running rampant on these trees. Yeah, they are. They're not just eating the leaves. The elephants are pulling down the branches. They're knocking the trees over. And Douglas Camaro, he's an ecologist at the University of Wyoming. And he says that these elephants have torn down so many acacia trees that they've transformed the landscape. Now we are seeing

like these areas opening up from the dance we're talking about in terms of those acacias to more open landscape, like a grassland or something like that. And he says elephants have cleared 70 to 80 percent of the trees in the park. And this is all over the last 20 years. Okay. We mentioned that this story is also about lions. So help us fit that part of the animal kingdom in here. Yeah, right.

So for the lions at this park, their favorite food is zebra. And the lions usually catch the zebras by hiding behind trees. trees, stocking them, and then boom, they pounce. And this open landscape, it means that they're losing the element of surprise. I mean, the zebras can now see them coming from across the field, and they get plenty of time to escape. So Camaro and his team actually found that the lions were almost three times better at hunting zebra in that tree-covered area, like what the whole park used to be, than on the open grassland that's there now. And this took years of fieldwork and observations and experiments to figure all this out. It's all detailed in the journal Science

this week. And one outside researcher who wasn't involved in the work told us that these connections in ecology can be really messy. But she was impressed with how well the study documented these links. Got a question for you. What does this all mean for the lions? I mean, if they can't catch the zebras, are they starving? Well, it turns out that there's actually some evidence that they're switching their diets. So as the proportion of zebra and their diet goes down the amount of buffalo has gone up. So that means that so far the lion population seems okay. Like their numbers are stable. There's still places in the park with tree cover where they're having decent lot catching zebras. But these tiny invasive ants are still taking

over the park at a rate of about 160 feet a year and it's not clear if they can be stopped. All right. Next up, I think you all have brought a story about something that does not sound particularly tasty to me. Stone age chewing gum. Yes. That's That's right. But Juana and Ping, I'm really curious. What's your opinion on gum? Like, do you love it? Do you hate it? I'm going to go with love it. I love bubble tape. I absolutely cannot stand it. Oh, no. I love gum. I have like packs all over my house and my car. But most relevant to the study, my teenager loves it too. Okay. I live with teenagers too. That sounds like something that could get very messy in a kid's room. But please explain. What do teenage gum preferences have to do with the Stone Age? So it's because the study published in the journal Scientific Reports looks at what teenagers ate in Scandinavia about 10,000 years ago. And this is all by analyzing the ancient gum they chewed. Okay. What flavor of gum are we talking about here 10,000 years ago?

Well, I mean, gum was a different thing back then. You know, basically it was tar made from the bark of birch trees. And people in the Stone Age used to chew a wad of this and then maybe like stick some tools together with it. And as you chew gum, in charge, general, it collects stuff from your mouth, you know, genetic material, bacteria, little bits of food stuck in your teeth. And so this Stone Age wad of gum is something like a time capsule of what they were eating. Okay. I am going to need to hear about the menu in Stone Age Scandinavia. Yeah, I was very interested. So I asked an archaeogeneticist at Sweden's Stockholm University about this, Anders Gatherstrom. Here's what he said people were snacking on in the Middle Stone Age or Mesolithic period. So what's the proper stone age diet?

At least now we know that if you go home and then put hazelnuts, trouts, and deer in your frying pan, then you would have a mesolithic diet from Scandinavia. And this gum also has like the imprints of teeth, which gives you the size of the teeth, which is also how they knew that the gum chewers were teenagers. And Gatherstrom and his team could tell from the mix of bacteria in the gum that one of the teens actually had very bad gum disease. We know that she was about to lose her teeth. Ouch. Although, I guess it's not super surprising that someone who lived almost 10,000 years ago needed some dental work.

Yeah, Gatherstrom said that she probably was in a lot of pain while chewing that gum. And while that's very sad for her, there's this little silver lining for researchers in the fact that we can learn so much detail of the daily life of a stone age person from a small piece of gum. Interesting. All right, let's move on now to cicadas. And I should just point out that this topic is such a big deal in my household. My husband absolutely loves cicadas, but I'm going to let you guys explain. Yeah, so scientists have determined that this spring, two adjacent groups of cicadas will emerge at the same time all across the Midwest and the Atlantic States, meaning billions of cicadas, at least. Our colleague Claire Marie Schneider wrote about this, and one entomologist she talked to described it as a spectacular macabre marty gras.

Okay, so this sounds like my kind of party, but I should note that not everyone would probably love this. So tell us, are these the kind of cicadas that come up every single? summer, or is this something more special? Okay, this is more special. I mean, there are annual cicadas, but these are more rare. So these two regional groups or broods of cicadas only emerge every 13 or 17 years. And the really exciting thing here is that the last time that these two specific broods, again, one on a 13-year cycle, the other on a 17-year cycle, the last time that they came up at the same time was in 1803. That is a long time ago.

Okay. Can one of you all remind me how their life cycle works? because 13 or 17 years, that is a long time to stay underground. It's a super long time, yeah. So periodical cicadas spend all of that time underground in this immature nymph form where they're sucking on the roots of shrubs and trees and feeding. And when that time comes, they emerge. They molt.

The males have this, like, glorious cacophony of calls and songs, which can actually be louder than a jet engine. And then the cicadas mate, the females lay their eggs in trees. And the cycle starts all over again, like when the eggs drop from the tree and return to the ground for another 13 or 17 years. So tell me, when exactly does the cicada Mardi Gras kick off? So one brood will start appearing in late April, mostly in the south, and the other will appear in mid-May around Illinois, Wisconsin, Indiana, and Michigan. All right, guys, I am setting myself a reminder to book a plane ticket back to the Midwest for that. Awesome.

Juana, thank you so much for hanging out with us. Happy to do it. You can also catch Juana on Consider This, NPR's Afternoon News podcast. Before we head out, a quick shout out to our Shortwave Plus listeners. We appreciate you and we thank you for being a subscriber. Shortwave Plus helps support our show and if you're a regular listener, we'd love for you to join so you can enjoy the show without sponsor interruptions. Find out more at plus.npr.npr.org slash shortwave. This episode was produced by Rachel Carlson, Gus Contreras, and Elena Burnett.

It was edited by Christopher Intellectual. Ljada, Viet Leigh, and Rebecca Ramirez. Rebecca and Rachel checked the facts, and the audio engineer was Stu Rushfield. I'm Regina Barber. I'm Ping Huang. Thanks for listening to Shortwave, the science podcast from NPR.