Short Wave - Like Humans, These Ants Can Perform Leg Amputations To Save Lives

Episode Date: July 10, 2024

Some ants herd aphids. Some farm fungi. And now, scientists have realized that when an ant injures its leg, it sometimes will turn to a buddy to perform a lifesaving limb amputation. Not only that — some ants have probably been amputating limbs longer than humans! Today, thanks to the reporting of ant enthusiast and science correspondent Nell Greenfieldboyce, we behold the medical prowess of the ant.Want to hear more cool stories about the tiny critters among us? Email us at [e-mail] — we'd love to know!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, shortwaver's Emily Kwong here. We humans, we have incredibly sophisticated kinds of medical care. Other animals, not so much. Like, researchers have seen evidence that some sick animals will self-medicate by eating clay or certain plants. But there is one creature in the animal kingdom who takes the practice of medicine, air quotes, medicine, to a whole different level. And that, my friends, is the tiny aunt. which really should not surprise us, right? I mean, ants are amazing. I mean, some ants farm. They farm fungi for their food. They herd aphids. I mean, if they've got agriculture, why not medicine?

That is NPR's number one ant enthusiast and science correspondent, Nell Greenfield boys. Hey there. Nell, we wanted to have you on the show because you recently reported on one aspect of ant medical care that is truly mind-blowing, at least for me, even if you're not surprised about it. That's right. I was kind of surprised about this, actually. despite my admiration for ants many abilities. So there's this new research out showing that ants will treat certain injuries with therapeutic amputation. Amputation. Just for comparison, how long have humans used amputation as a medical treatment?

So if you look at evidence like in the archaeological record, you can find ancient human skeletons with clear amputations that go back like over 30,000 years. So a long time. But the ants have probably been doing it for longer, much longer than us. And these aren't like super rare ants or anything. These are like common carpenter ants you can find in people's backyards in places like Florida. So in someone's backyard right now, a tiny ant surgeon is effectively practicing Civil War era medicine, aka amputation. Yeah.

And I mean, the Civil War medicine thing is a pretty good analogy because ants engage in battles and warfare. I mean, they hunt, they defend their territory. And that means when ants come home back to the nest, they can be injured. And it turns out their nestmates take care of their wounded warriors. I mean, lab experiments show that their medical efforts, including now we know, amputations, are very often life-saving. And it turns out the ants are selective about when they perform amputations. They're not just like hacking off injured legs willy-nilly.

All right. Well, today on the show, we dive into the ant hill to check out their health care system. How scientists discovered that ants will perform medical acts that include clinical amputations and how the ants determine whether or not an injured limb has got to go. You're listening to Shortwave, the science podcast from NPR. Okay, now, so how did scientists learn that ants will sometimes treat an injury with amputation? So the lead researcher who did this work is named Eric Frank, and he's now at the University of Würzburg in Germany. And he's really a tropical biologist. So years ago, he was studying some ants in Africa that will hunt and eat termites.

And I talked to him back then, and he told me that ants scouts would go out and find a termite nest. And then hundreds of ants would march out together, like an army in formation. Like three ants next to each other in a two meter long column. It's very peculiar. It looks like a long snake walking on the ground. So when the ants get to the termites, they would fight. There's like this huge battle. And when it was over, he would see the ants start picking up dead termites to carry home for food.

But then he noticed that some of the ants that were marching home weren't carrying termites. They were carrying other ants, wounded ants. So they were carrying their fallen comrades home? Yeah, basically. Just like soldiers, you know. Yeah. Instead of no man left behind, no ants left behind. Exactly. And so he was really surprised by this. And he did a study where he marked the industry. injured ants to see what happened to them. And it turns out in nearly every case, the injured

ants that were carried home made a full recovery. We saw them again participating in hunts the next day. What a rebound. Yeah. So he got interested in how they recovered. And by studying this, he learned that ants will lick and groom a buddy's wound in the hours after the injury. And without this treatment, the injured ants would usually die. So it turns out this particular species of ant has a special gland that's full of antimicrobial secretions. And worker ants basically apply these secretions to the open wounds of their nestmates. It's basically like giving their injuries antibiotics. But are these the ants that engage in medical amputation? No. Okay. So that's something Eric Frank only observed more recently. And when I talked to him, he told me it was because of the pandemic

because he couldn't travel. So he started studying this other ant. And The common name is the Florida carpenter ant. I feel like so many scientists had to make do during the pandemic, you know, people learned cool stuff just by studying what was around, which in his case was the Florida carpenter ant. It's true. I wish somebody would put like a compilation of like pandemic desperation science where like scientists looked around and saw what was there. Anyway, so he's now looking at this other ant and he knew that this species did not have that special glands that he'd been studying before. So I just very naively wondered, well, how would they act if they get confronted? with injuries. So these are, you know, injuries that they did experimentally in a controlled way in the lab, right?

And pretty much right away, he and his colleagues saw ants amputating their buddies injured legs. This has been my big question this whole time. When you say amputating, how does that work? Ants don't have tiny little bone saws and surgical tools. No, they don't. Okay, so here's what happens. An injured aunt, you know, an aunt with an injury and like the upper part of its leg, will present that leg to a nestmate. And this nestmate will lick at the wound with their little mouth parts, you know, like sort of move up to the shoulder area, and like up at the joint, like start chewing through the leg to sever it. And this takes a while, like many minutes. And you can see the other one not moving, not really flinching and accepting it. And once the leg is removed

and it falls off, the other one will come back and lick the little stump that's left and it will still be presenting it. So it's clearly collaborating and wants the same thing as the one that is treating it. So either the injured ants are just stoic or they don't feel pain or what, but they're clearly working together to make this thing happen. The depth of ants, I just didn't realize any of this. And you said earlier that this procedure, for lack of a better term, is life-saving. How do researchers know that? So they found that ants with similar injuries that were kept away from their nestmates. They didn't get amputations. Those ants frequently die. So, you know, no amputation, high chance of dying.

And their studies show that's because without amputation, an infection from an open leg wound can travel to the rest of the ant's body and kill it. And Eric Frank told me to see if it was really amputation, that was the key thing. He figured he'd just try his hand at performing ant surgery. Since I observed these amputations, I was like, well, I'm pretty sure I can artificially conduct the same kind of amputations. And so even when it was done by a human, the amputation treatment was just as effective in helping injured ants recover. Really confirming that these amputations were saving the lights of the infected individuals. Pretty cool, right? So cool.

But wasn't there supposed to be some clinical judgment involved here you alluded to earlier that ants aren't just whipping off legs right and left? They are making decisions about what to amputate. Well, decisions. I mean, that's a debatable word. But, yeah, there is a part of this that the researchers found perplexing for a while. they had been studying ants with injuries to the upper leg and witnessing amputations at the shoulder. And so after they'd done this for a while, they were like, okay, what if an ant had an injury farther down, like towards its little like ant foot? Okay.

So it turns out that for injuries lower down, like what would be the human shin, the ants did not amputate legs at all. So amputation was only occurring when the injury was high up in like what would be. would be a human thigh. I was like, what, what, it doesn't make sense. And it took Eric Frank and his colleagues like a year of lab work to figure out what was going on. And basically, the important thing is that the body of an ant is just not like the human body. How so? Well, they don't have hearts like we do, for one thing. There are these muscular pumps distributed throughout the ant's body, including in its legs, especially in the thigh, the upper leg area. So it's weird, but like what it means is that if an ant gets injured in that upper leg area, the muscles are damaged.

And so the pumping of liquid doesn't happen as quickly. And that means infection actually spreads slowly, more slowly than it would if the injury was lower down on the leg. And so basically what it means is that amputation really only has a shot at blocking the infection for upper leg injuries, even though it doesn't seem like it should be that way, but that's how it is for ants. Right, and then if the infection is lower down on the leg, the infection kind of spreads fast, the amputation can't work, and it's deemed a little bit of a lost cause. Yeah, so the researchers tested all of this experimentally in the lab, and they showed, you know, experimentally that amputation is not effective for lower leg injuries. And so that's why the ants don't do it. They are like doctors. They're like surgeons.

So for those injuries, they just spend a lot of time tending to the wounds, licking them, and whatever they do. do is often life-saving. It's amazing to me that this treatment is so targeted to a specific kind of injury. They are making what we would call a clinical evaluation. Yeah, but, you know, they're not exactly like doctors. Like, you know, it's not like they're sitting there thinking about it and weighing the pros and cons. I talked about this with some other ant experts who weren't involved in this study, like Daniel Kronauer. He's at Rockefeller University. And he told me, you know, remember, this is evolution working, not like individual. ants with like medical degrees and medical knowledge.

They have basically evolved over like thousands and thousands and probably millions of years to be kind of programmed in quotation marks to react to different kind of injuries in a certain way. It's all to help the colony as a whole survive. And he told me, you know, besides these antimicrobial secretions and amputations, ants sometimes do other things that seem a lot like human public health measures. So for example, there's studies showing that if ants in a nest have, certain contagious infections.

The social networks of the nest will sort of get reconfigured. There's less connections. Like, everything becomes much more modular. So they'll quarantine, essentially. Yeah. You basically socially isolate individuals that carry an infection. That's, of course, you know, reminds you of the COVID pandemic maybe and what we were supposed to be doing.

And then there's other studies showing that ants with an infectious disease might just wander off from the colony and, like, go die somewhere else. Oh, that's very self-sacrificing of that ant. And, you know, again, the amputation and antibiotic parts, it all sounds very caring. Yeah, but, like, it's not like it's love. It's not, like, empathy or anything. It's just that, like, saving ant lives means that the colony has bigger armies and more success, just generally speaking, right? That's, like, one more soldier for your cause. Right. Okay. I'm hearing you. This is Evolution at Work. These are adaptive strategies for the good of the colony,

self-isolation, amputation, wound-licking. It's all very cool. And I guess what's striking to me is, given how useful it is, how have we not noticed this before? I mean, we've been living alongside Carpenter ants for a long time. Yeah, I am sure people listening to this have seen these ants before, right? And they're not like the little black ants that invade your picnics, but the Florida Carpenter ant is, you know, this brownish ant like a centimeter across. It's like in lots of places where people live. And, you know, that is the part that really struck this other guy I talked to an ant expert called Clint Pennick. He's at Auburn University. This is an ant that I grew up with in my backyard. And so it's really interesting to see such a sophisticated behavior, you know,

that's literally happening in people's backyards from a common carpenter ant. It makes me wonder, like, what else the ants are doing? Insects in general feel like the final frontier to me. There's so much we don't know about what they do. And I hope when you find something else, you come on the show and talk about it, no. Absolutely. I mean, I do admire your seemingly endless desire to hear this stuff. And, you know, if I know ants, like pretty soon we're going to be hearing about something else, there's going to be another supposedly unique to human activity that it turns out, oh yeah, ants have been doing for millions of years. Yeah, I mean, what would be really weird is if they had their own science podcast. I mean, it would be serious competition for you, I got to say, because I would listen to that all day long,

all day long, Emily. I would love to co-host with Ann. This episode was produced by Hannah Chinn. It was edited by our showrunner, Rebecca Ramirez, and fact-checked by Nell Greenfield-Boys. Beth Donovan is our senior director, and Colin Campbell is our senior vice president of podcasting strategy. I'm Emily Kwong.

Thank you for listening to Shortwave, the science podcast from NPR.