How scientists discovered that animals are doctors, too

When people are sick, we seek out medications and treatments to help heal. For a long time, scientists thought that was a uniquely human ability. But it turns out, many other animals do a version of it too! And since the late 1980s, western researchers have been trying to get a peek behind the curtain. And aside from just cataloguing all the cool examples just to know, there’s a real hope that studying animals’ medical cabinets may be the most promising way to expand our own. We get into the weeds with freelance science journalist Mandy Nguyen https://www.mandynguyen.com/. Interested in more animal stories? Email us your ideas and questions to explore at [email protected] mailto:[email protected]. They may become a future episode! Support public media with NPR+ and enjoy perks for over 25 podcasts like this one. This show’s perks include sponsor-free listening. Learn more at plus.npr.org http://plus.npr.org. See pcm.adswizz.com https://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 https://www.npr.org/about-npr/179878450/privacy-policy

• 0:00Speaker 00

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• 0:12Speaker 01

  You're listening to Short Wave from NPR.

• 0:18Speaker 02

  Hey, Short Wavers. It's Nate Rott with science journalist Mandy Nguyen.

• 0:22Speaker 01

  Hi there.

• 0:23Speaker 02

  Hey. Okay. Today, you're bringing us a story on animal behavior, specifically what animals do when they get sick.

• 0:30Speaker 01

  Yeah, so when we humans get sick, we take cough syrup, antibiotics, you know, we have thousands of treatments for thousands of ailments.

• 0:38Speaker 02

  For sure, yeah.

• 0:39Speaker 01

  And for a long time, scientists thought medicine was a uniquely human trait. There's a famous quote by one of the physicians who founded the Johns Hopkins Hospital. He said, "The desire to take medicine is one feature which distinguishes man, the animal, from his fellow creatures."

• 0:55Speaker 02

  Sounds very much like a guy that founded Johns Hopkins would say, you know, very lofty.

• 1:00Speaker 01

  But yeah, it's like a common through line in the history of science to think that humans are very special. But there's a whole field of growing research showing that a lot of other animals treat themselves, too.

• 1:10Speaker 03

  It's goats, and it's bears, and it's porcupines, and it is ants, and it's bees, and it's fruit flies. So I think the more we look, the more we find that animals can use medicine.

• 1:21Speaker 01

  That's Yap DeRota. He's a biologist at Emory University. And he and other scientists in this field are looking at how animals heal themselves when they're feeling under the weather.

• 1:30Speaker 02

  Whoa, cool. So give me some examples.

• 1:32Speaker 01

  So they've studied how bears chew on willow bark to relieve their post-hibernation aches, how apes apply chewed-up leaves to their wounds.

• 1:40Speaker 02

  Whoa.

• 1:41Speaker 01

  And even how some ants perform surgery on other ants to prevent infection from spreading through a colony.

• 1:47Speaker 02

  Like surgery on another ant? What does that even mean? Like, they cut off their limbs, or what?

• 1:51Speaker 01

  It means they chew it off with their mandibles.

• 1:54Speaker 02

  Oh, dude. All right, hardcore. Let's go, ants.

• 1:58Speaker 01

  Exactly. There's just this whole other world of wild animal medicine, one that's as complicated and important as our own. And scientists like primatologist Elodie Freiman at Brown University are helping us uncover it.

• 2:11Speaker 04

  Across the animal kingdom, self-medication and medication by animals take so many different forms. It depends on the species, it depends on the behavior, and it depends on the medicine.

• 2:21Speaker 02

  So today on the show, animal doctors: how they treat themselves, each other, and what we humans can learn from them. You're listening to Short Wave, the science podcast from NPR.

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• 4:01Speaker 02

  Okay, Mandy, so taking a step back, how did scientists even learn that animals could use medicine in the first place?

• 4:07Speaker 01

  Well, it started with an observation in 1987. Biologist Michael Huffman was following a group of chimps in Tanzania. He was studying what they ate, how they behaved, the way they interacted with each other, when he noticed something new. So one of the mothers of the group, named Chowseku, was eating something that she usually didn't. It was a tropical shrub. It was called the bitter leaf plant. And this plant is usually kind of toxic, so it's not a regular part of their diet.

• 4:34Speaker 02

  Whoa, so could it have just been like a random craving for like a bitter taste in the same way that I desire sweets every hour of the day?

• 4:41Speaker 01

  I mean, maybe.

• 4:43Speaker 02

  Okay.

• 4:44Speaker 01

  But the thing that Michael took note of was that she was acting differently. She was lethargic, and she seemed sick.

• 4:49Speaker 02

  Gotcha.

• 4:50Speaker 01

  She also was eating this plant in a really specific way. She would peel off the bark and the leaves, and then chew and suck at the juicy kind of inside part, and then she would spit it out, like all the fibrous parts.

• 5:01Speaker 02

  Oh, so like, not really eating?

• 5:03Speaker 01

  Exactly.

• 5:03Speaker 03

  Turns out, it's a widely-used medicinal plant by humans, treating very similar symptoms that Chowseku was showing and that she recovered from in 24 hours, roughly the time that humans recover from illness when they use that plant as well, and particular intestinal upsets, malaria.

• 5:22Speaker 02

  Wow, so this is something that people have been using, too?

• 5:25Speaker 01

  Right. And Michael only learned this because of his guide, who was a game officer at the Mahali Mountains National Park. His name was Mohamedi Kalunde. And he said, "It wasn't just this one plant they used." Mohamedi told him...

• 5:39Speaker 03

  Oh, yeah, my ancestors, my grandfather, my mother, all of my mentors in traditional healing have stories about plants named after the animals that they saw use and treat themselves for sickness. And I literally almost fell off the log that I was sitting on in the mountains, and I was talking with Mohamedi about it.

• 6:01Speaker 01

  Michael immediately started wondering what other hidden knowledge animals had.

• 6:05Speaker 02

  Yeah, but I imagine that, like, other Western researchers that Michael was talking to were maybe skeptical of this?

• 6:11Speaker 01

  For sure. I mean, when he came back to camp after watching Chowseku and told the others on his research team, no one better than I.

• 6:18Speaker 03

  First thing that I got back from my senior colleagues in camp was, "Oh, we've seen the chimps eat that all the time. Wild animals never get sick."

• 6:27Speaker 02

  But that sounds so intuitively wrong. I mean, like, an animal never gets sick? We are animals, right? One. And like, my dog gets sick, I feel like, every other week.

• 6:37Speaker 01

  I mean, yes. But keep in mind that this is the 80s. This sort of thing was unthinkable to most scientists back then.

• 6:45Speaker 02

  Okay.

• 6:46Speaker 01

  Plus, drawing a hard line between food and medicine is also kind of difficult. Like, even in our own diets, food and medicine overlap. Chicken soup is a staple for a cold, but I'd eat it just because it's good.

• 6:57Speaker 02

  I would eat it, too, because I love chicken noodle soup. So it's a question of, like, are they eating it because it's just food, or because they actually want to treat an illness or a disease?

• 7:07Speaker 01

  Right. And it takes a lot of following around chimps to figure it out. So Michael had to sample a lot of chimp poop to test for parasites, to prove they were sick, and then watch their behavior to see if they sought out particular plants when they were. Then the chimps had to actually get better. His team also tested the bitter leaf itself to see if it had any bioactive compounds, and it did. It had about 13 chemicals new to science at the time.

• 7:32Speaker 02

  Whoa.

• 7:32Speaker 01

  So it took Michael a decade of more work to prove that his suspicions were true, and to confirm what his guide and plenty of traditional healers already knew, that animals use medicine on themselves.

• 7:44Speaker 03

  And of course, the animals themselves have known about it forever and ever.

• 7:49Speaker 02

  Animals are wise. I agree with that.

• 7:51Speaker 01

  Mm-hmm. And since then, scientists have realized, or realized again, that all kinds of animals use medicines or treatments. We're talking cats and dogs, bears, lizards. And it's not just medicinal plants that they're making use of. Lots of animals, like buffalos, elephants, and primates eat dirt, which might strengthen their immune systems by diversifying their gut microbiome. Over 200 species of birds do something called "anting," which is when they take ants in their beaks and rub them on their feathers, so that the ants spray formic acid, which kills lice on them. Dolphins might also rub themselves against corals and sponges to treat skin diseases.

• 8:34Speaker 02

  Well, yeah, I think I've heard about that. I mean, I feel like, you know, apes and monkeys, they're very similar to us, right? Just a little hairier. So it's like easier to picture them using medicine, but like, lizards, dolphins, and birds, too?

• 8:48Speaker 01

  Yeah. And I'm going to take us a step further, because it doesn't just stop with animals like lizards and birds. Insects can do this, too.

• 8:56Speaker 02

  Whoa.

• 8:56Speaker 01

  For example, monarch butterflies.

• 8:59Speaker 03

  Just a few decades ago, there were still a lot of scientists who said, "There is no way that monarch butterflies can do that, because they're just not smart enough. They've got these tiny little brains."

• 9:09Speaker 01

  That's biologist Yap DeRota again. And he says that medication in insects is a lot easier to study, because it's easy to keep a lot of them in a lab and study them directly.

• 9:18Speaker 02

  Oh, yeah, that checks out. I mean, you can get specific bugs sick and see if they go for a certain kind of plant that their non-sick friends don't?

• 9:27Speaker 01

  Yeah, and that's exactly what he did, specifically with monarch butterflies and milkweed. Monarchs lay their eggs exclusively on milkweed, because that's the only thing their caterpillars eat. Sometimes they lay their eggs on a kind of milkweed that's known to be toxic. And part of why they do so is because the toxins the caterpillars consume, it helps them repel predators when they're butterflies.

• 9:47Speaker 02

  Whoa, cool.

• 9:48Speaker 01

  But Yap thought that another reason that they might be doing so was as a way to treat parasites intentionally.

• 9:55Speaker 02

  And I'm guessing our guy Yap was correct?

• 9:58Speaker 01

  Yes. So his team released parasite-infected butterflies and healthy ones in a big flight cage with both kinds of milkweed to see where they laid their eggs. And the infected butterflies laid a lot more eggs on the toxic milkweed.

• 10:12Speaker 02

  And did they get better?

• 10:13Speaker 01

  Well, actually, this does nothing for the infected butterfly who laid her eggs. She's not eating the toxic milkweed or anything. But it helps the babies that she passes the parasites to.

• 10:23Speaker 03

  What she can do is essentially preventatively cure her offspring that are going to be infected in the future. And I think that's something that insects have told us, is that...

• 10:35Speaker 06

  Animals medicate not just themselves, but each other.

• 10:39Speaker 01

  Other insects do this, too. Some bees mix antimicrobial tree resins and wax to line their hives if there's an infection to counter the spread.

• 10:48Speaker 02

  Whoa.

• 10:48Speaker 01

  And there are Florida carpenter ants that do lifesaving amputations on other ants in their nests that have infected wounds.

• 10:55Speaker 02

  Are metal ants? Heck, yeah. So even the smallest, like, tiniest-brained little creatures use medicines in all sorts of ways.

• 11:03Speaker 01

  Yeah, and they can treat each other.

• 11:05Speaker 02

  I mean, this is all super fascinating, but I'm wondering, like, beyond being cool, can any of this information help people? Am I just being too selfish?

• 11:14Speaker 01

  So there are actually a lot of practical applications for this research. So the first area is in how we manage our domestic animals and livestock. For example, honeybees. There's a whole industry around them as pollinators for agriculture, but they're at risk of die-offs. Knowing that they line their hives with, you know, the sticky medicinal resin and wax for medicine, it should encourage beekeepers to facilitate that process instead of cleaning it away, which is what's usually done.

• 11:40Speaker 02

  Huh.

• 11:41Speaker 01

  And with livestock like sheep and goats, we usually give them drugs when they're sick. But overreliance on drugs like antibiotics has caused widespread resistance to them. These animals also know how to self-medicate. And scientists say that we should help them help themselves by diversifying their access to medicinal plants and foods in pastures. So healthier animals also means healthier people.

• 12:04Speaker 02

  I dig it. Okay, so knowing that animals use medicine means better care of the animals that we live with and manage, better results for us. What else?

• 12:13Speaker 01

  So the second thing has to do with finding new medications. Primatologist Elodie Fryman, one of Michael Huffman's former students, says that there's a lot of potential here.

• 12:23Speaker 04

  I think a lot of people don't realize just how many of our modern-day pharmaceuticals are derived from or inspired by natural products, meaning medicinal plants, medicinal resources that exist in nature.

• 12:38Speaker 01

  Like aspirin is derived from the bark of willow trees. And penicillin, our first antibiotic, is from a fungus. And so by looking at animals, scientists might be able to find potential medicines in places we've overlooked. And in fact, they already have. By studying chimps in Uganda, scientists have found two antimalarial compounds new to science. And the chemicals of the bitter leaf plant that Michael Huffman was studying, all the way back in the 80s, scientists have looked at its effects on various kinds of cancer. And it was shown to inhibit tumor growth.

• 13:08Speaker 02

  Dang, so maybe I should start paying more attention to like what grass my dog is eating when he gets an upset tummy, right? Or try to learn from him.

• 13:15Speaker 01

  I mean, that's basically what researchers like Elodie are doing.

• 13:19Speaker 04

  It's not like we have people medicine and animal medicines. A lot of these medicines are shared in these kind of complex ecosystems that we're all existing in. And oftentimes, when animals have found a medicine, we've found them as well, and vice versa.

• 13:35Speaker 01

  When Elodie's in the field, she works a lot with local healers to see if they recognize the plants and treatments that the animals use. And she's come to realize that the planet is just one big, shared medical cabinet.

• 13:46Speaker 04

  That also has a really important conservation implication, because it means that if these medicinal resources start to disappear, it's not just animal health care that's at risk, it's also human health care as well.

• 14:00Speaker 01

  I personally think this is a beautiful, fascinating science that shows us another thing we have in connection with a lot of the animals around us. It's another way that their health and our health and the health of the planet is interconnected.

• 14:11Speaker 02

  Turns out, we're all on this same spinning rock together, right?

• 14:16Speaker 01

  Turns out.

• 14:18Speaker 02

  Mandy, uh, thank you so much for taking us on this tour of the amazing world of animal medication. I learned a lot.

• 14:26Speaker 01

  Thank you.

• 14:28Speaker 02

  If you liked this episode, please share it with a friend. It really helps out our show. This episode was produced by Hannah Chin. It was edited by Hannah as well, and Rebecca Ramirez. Tyler Jones checked the facts. Jimmy Keely was the audio engineer. I'm Nate Rot. Thanks for listening to Short Wave, the science podcast from NPR.

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