How A Woodpecker Pecks Wood, And How Ants Crown A Queen

Is it all in the hips? Scientists break down woodpeckers' head-hammering moves. Plus, what makes one ant a queen and another a worker?

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Flora Lichtman?

  I'm Flora Lichtman and you're listening to Science Friday.

• 0:07Flora Lichtman?

  Today in the show, how do you drill a hole with your head?

• 0:11Speaker 01

  They're engaging everything from head and neck muscles, which you might expect, all the way down to muscles in their tail and hips.

• 0:22Flora Lichtman?

  If you have heard the hammering of a woodpecker in the woods, you may have wondered, how do they do it? What does it take to whack your head against a tree repeatedly, hard enough to drill a hole? Well, a team of researchers wondered that too and set out to investigate by putting tiny muscle monitors on eight downy woodpeckers and watching them with high-speed video as they pecked away in the lab. Joining me now is one of those researchers, Dr. Nick Antinson. He's an NSF postdoctoral research fellow at Brown University and an author of a report on the work in the Journal of Experimental Biology. Nick, welcome to Science Friday.

• 1:00Speaker 01

  Thank you, Flora.

• 1:01Flora Lichtman?

  Okay, I love this question, but why this question?

• 1:05Speaker 01

  Yeah, so what we were really excited about with this question in particular is, you know, all birds peck, but woodpeckers are really special in that they take this to the extreme. And by investigating extreme behaviors, we can kind of figure out what the performance limits are of what things like muscles are actually able to do.

• 1:28Flora Lichtman?

  When you say that woodpeckers take it to the extreme, how hard do woodpeckers peck?

• 1:35Speaker 01

  A woodpecker can peck at about 20 to 30 times their body weight. What it feels like if you get pecked by one is it feels like a sharp pin prick. That's actually really impressive for a bird that weighs about as much as a single AA battery.

• 1:51Flora Lichtman?

  Well, I was gonna ask, I mean, 20 to 30 times your body weight, is that a lot? Like, when I'm hammering, am I hammering as hard as a woodpecker or harder?

• 2:00Speaker 01

  So you would be hammering probably harder than what a woodpecker does. But with the woodpeckers, what's interesting is it's all of that hammering force down to a pinpoint. And so that's what we were really excited to set out to investigate here. It's so much more than the force that your normal bird pecks with.

• 2:18Flora Lichtman?

  So what did you find? What is driving this drilling power?

• 2:21Speaker 01

  I think one of the most stunning things that we found in this study was that it's muscles across the body of the woodpecker. And so they're engaging everything from head and neck muscles, which you might expect, all the way down to muscles in their tail and hips as they push forward during these strikes.

• 2:41Flora Lichtman?

  I mean, this reminds me of my high school soccer coach, who would often tell us that if we were doing a header, we had to use our whole body.

• 2:49Speaker 01

  Yeah, absolutely. You just build more force that way. And the other thing that was really exciting with this, too, that I'm sure your soccer coach probably also would have recommended, is to grunt while you do it. And so the woodpeckers do that, too, where they're actually grunting through each one of these strikes.

• 3:06Flora Lichtman?

  Can you hear it?

• 3:08Speaker 01

  So you can't hear it. It unfortunately gets masked by the percussion of the drum beats that they're making. But we were able to actually measure the respiratory pressure from their respiratory system to tell when these birds were exhaling versus when they were inhaling.

• 3:25Flora Lichtman?

  So that's what you mean by grunt? They did like a big exhale?

• 3:29Speaker 01

  Yes, they exhale straight through the strike, similar to how, you know, an athlete like Serena Williams will when she's striking a tennis ball. What happens is by stabilizing those core muscles while you exhale, you can add extra power to those strikes in all of those instances.

• 3:45Flora Lichtman?

  The grunt is making them stronger?

• 3:48Speaker 01

  Yes, so the grunt is actually making them stronger.

• 3:51Flora Lichtman?

  Can you, can you make the sound for us? Like what you would imagine it to sound like?

• 3:55Speaker 01

  I can, I can give it my best shot. The other thing that's interesting about it, that I'll just add to that before I make the sound, because it'll give some context to the specific sound I'm making, is that they can do this repeatedly as well, and up to like 13 times per second. They can exhale on every single one of the strikes. And so if I were to kind of make the sound, I think it would sound something like So to us, that sounds like hyperventilation. But to them, this is just like well within their respiratory capabilities.

• 4:27Flora Lichtman?

  Amazing. How do they deal with kickback? Like, why don't they fly backwards after they hit the tree?

• 4:34Speaker 01

  Yeah, so another one of the really exciting things we found is that when these birds are going in for these strikes, the first things they do is they'll activate the neck muscles that pull the head forward. Then it's the hip flexors to pull the entire body forward. Then their tail pushes against the tree as a brace. And then following that, there's a collection of head and neck muscles on the back of the head that actually stiffen. And so, right as they're going into that strike, they engage those abdominal muscles to exhale and then push their way into the wood. And so they're not just bouncing off and their neck's not just like collapsing as they take the force of basically a car crash.

• 5:18Speaker 01

  They're powering their way into the strike and then they very measuredly just pull themselves back out and inhale as they're pulling themselves back out.

• 5:26Flora Lichtman?

  Wow, there sounds like there's a lot of choreography here. Muscle choreography in their bodies to achieve this.

• 5:33Speaker 01

  Absolutely, and we looked at this as well, specifically with the repetitive strikes that these birds are performing, where they're pecking multiple times in a row without taking a break. And one of the really striking things that we found in doing that was that the timing of when they're activating each of these muscles in sequence was incredibly precise. And so there was never kind of a misfire where one muscle fired out of order where it wasn't supposed to.

• 6:01Flora Lichtman?

  Hmm, let's talk about the experimental setup. Was it difficult to get the woodpeckers to peck in the lab?

• 6:09Speaker 01

  So the woodpeckers are voracious and so they actually love to peck on any wood that you provide for them?

• 6:15Flora Lichtman?

  As many homeowners know.

• 6:18Speaker 01

  As many homeowners know, yes. So in order to collect the data, we had these birds hooked up to their sensors and then those sensors actually went to a custom-made backpack for each bird so that it comfortably rested on their back so that they could freely move throughout our recording chamber and peck on kind of a variety of woods. So we gave them kind of a charcuterie board of different woods to peck from.

• 6:45Flora Lichtman?

  Are there any other special adaptations that a woodpecker has to live this pecking lifestyle?

• 6:53Speaker 01

  Yeah, so I think one of the most exciting other things that we've found with the woodpeckers was that they can exhale on every single one of those strikes. They can exhale at a rate of 13 times per second and then as they're pulling away with each strike, they can inhale on the order of 40 milliseconds, which is less than the blink of an eye, to take a quick breath in and get ready to oxygenate all of those muscles and their airways between each one of those strikes. And in birds, this is really only a respiratory adaptation we've seen to this point in songbirds when they're doing their singing behaviors. They can intersperse these little inspiration breaths between each one of the syllables

• 7:38Speaker 01

  of their song. And so woodpeckers aren't very closely related to songbirds. And so it's really interesting to find that woodpeckers have found a similar adaptation for their pecking behaviors.

• 7:51Flora Lichtman?

  Okay, while I have you, Nick, I have a very important question. I've heard for many years that the tongue of a woodpecker wraps around its brain and the purpose of that is that it's a shock absorber. True?

• 8:08Speaker 01

  No, so actually that it's become a very popular science myth. And so

• 8:13Flora Lichtman?

  I'm this is the second gasp. I've gasped twice.

• 8:18Speaker 01

  So what's interesting about this is their tongues do wrap around their head, but they wrap around the outside of the skull. And so they're not providing kind of the cushioning to the brain. The brain is still smacking against the front of the skull when they're doing these repetitive impacts. What the tongue wraps around the skull for is actually to be a projectile. So they can actually shoot their tongues like chameleons can to spear insects in the holes that they've drilled in trees.

• 8:46Flora Lichtman?

  To spear them?

• 8:47Speaker 01

  Yeah.

• 8:48Flora Lichtman?

  They're pointy at the end?

• 8:50Speaker 01

  Yes. So at the end of a woodpecker's tongue, there's a barb so that they can skewer through those insects.

• 8:57Flora Lichtman?

  I love these birds so much. So are they wrapping? Is it just that it's a convenient place to hold the tongue?

• 9:05Speaker 01

  Yeah, it's a convenient place to store a really long tongue. With some woodpeckers, their tongues can even be three times the size of their head.

• 9:14Flora Lichtman?

  Wow.

• 9:15Speaker 01

  The other thing I'll mention about this, too, is that the reason that woodpeckers don't get concussions, or at least as far as we've seen so far, is because their brains are small enough that they don't build the G-force to smack against the front of the skull that would be necessary to cause a concussion.

• 9:32Flora Lichtman?

  Is this just a force equals mass times acceleration thing? Like, small mass equals small force?

• 9:38Speaker 01

  Exactly. The forces that the brain is smacking the front of the skull with aren't actually enough to cause a concussion because their brains don't weigh very much.

• 9:47Flora Lichtman?

  Gotcha. This is so fascinating, Nick. Thank you so much for taking the time to talk with us today.

• 9:52Speaker 01

  Thank you for having me.

• 9:54Flora Lichtman?

  Dr. Nick Antinson is an NSF postdoctoral research fellow in the Department of Ecology, Evolution, and Organismal Biology at Brown University.

• 10:04Flora Lichtman?

  We have to take a break, but don't go away because when we come back, what does it take to be a royal ant, that is? Turns out how ant queens are crowned is a hot topic in entomology circles. Stick around.

• 10:25Speaker 02

  WNYC Studios is supported by Wise. Wise, the smart way to manage the currencies you need around the world. With a Wise account, you can send, spend and receive in up to 40 currencies with only a few simple taps. Be smart, get wise. Download the Wise app today. Terms and conditions apply. Support for Science Friday comes from the William K. Bose Jr. Foundation.

• 10:52Flora Lichtman?

  Turning now to another heady creature question. How do ant queens get crowned? This is a royal mystery because, and this is wild, you can take two ant eggs with exactly the same genes and one can grow up to be a queen and the other a worker. How does that happen? It turns out that's a hot topic in the ant world and a recent paper provides some insights. Here to tell us more is study author Dr. Daniel Cronauer, an evolutionary biologist at the Rockefeller University in New York City. Daniel, welcome to Science Friday.

• 11:28Speaker 03

  Thank you very much.

• 11:29Flora Lichtman?

  You study the social lives of insects. What drew you to this particular ant hill?

• 11:36Speaker 03

  Well, I've been really fascinated by insects since I was a little kid. So I grew up in Germany, in Heidelberg, as you might be able to tell from my accent. And my mom tells the story that she often couldn't find me doing elementary school pickup because it turned out that I was punched over in some hedge watching ants on the floor or looking at a beetle or something. You know, when you, when you watch insects, they just look very exotic and, and almost like on a different planet or like some, some alien creatures. And for me, that was always very fascinating, like thinking about how they experience the world and how they communicate and, and what their behavior means to them and how they live.

• 12:20Speaker 03

  And then I made that early childhood fascination my profession.

• 12:25Flora Lichtman?

  So your latest study is about how a queen ant becomes a queen, which I take it is kind of mysterious and a little bit of a hot topic in the ant world.

• 12:35Speaker 03

  Yeah. So the interesting thing is that in an ant colony, you can start with, say, two eggs that are genetically identical. And depending on how you treat those individuals during the larval stage, when they're growing up and they feed a lot. They can develop into either a queen, which is very large, lays a ton of eggs, lives quite long in some species for decades. Or you can raise it into a worker, which is small, usually can't lay eggs or doesn't lay eggs, lives only for a few months often, and performs all the other tasks in a colony. So from one genome, you can make very, very different types of organisms.

• 13:15Flora Lichtman?

  Like stem cells?

• 13:16Speaker 03

  Exactly. I was about to say, right? It's a little bit like you start with a stem cell and then you make either, say, a neuron or a skin cell, right? And that's actually the analogy that you hear a lot when you read about insect societies, the analogy of the insect society as an organism, or sometimes people talk about the super organism.

• 13:36Flora Lichtman?

  The super organism. So do we understand what determines whether that ant egg becomes a queen or a worker?

• 13:47Speaker 03

  Yeah, so there's a lot of research that's being dedicated to that still, and it has a lot to do with how much food the larva gets. And so the workers can feed a larva more or less food, or they can feed it different types of food. You might have heard of royal jelly in honeybees. So if a larva gets fed a lot of royal jelly, it tends to develop into queen. So ultimately, it's, it has a lot to do with what size the larva reaches and how large it can grow.

• 14:13Flora Lichtman?

  But who's determining how much food that larva gets? Like, and are all the larvae getting the same amount of food and some just get bigger than others and become the queen?

• 14:22Speaker 03

  Yeah, so it's a bit complex, right? Like, I think the simplest scenario is that the workers who feed the larvae, right? They go out, they forage, they bring food back, and then they give the food to the larvae. Those are the ones that kind of decide how much food the larvae get. And so what a lot of ant species do is that they raise new workers or new queens in separate cohorts. So, you know, sometimes in the spring, you see kind of winged ants that kind of fly around. Those are queen adds, the bigger ones.

• 14:53Flora Lichtman?

  Oh, so you can have multiple queens in a generation. It's not one that's being picked out.

• 14:57Speaker 03

  No, exactly. So most ant colonies, you know, they have often one queen in the colony that lays the eggs. But when they raise queens, they raise many, many queens, like often hundreds, sometimes thousands. And those queens, they have wings initially, and then they go on a mating flight. Then they mate, then the males usually die and the queens shed the wings. And then they start to dig a little hole in the soil and they found a new colony. And then you have a new colony that has one.

• 15:23Flora Lichtman?

  Okay, so we know that size is a biggie for determining how that queen program is going to get switched on in an ant. And size is determined by genes and by the environment. But your new study in clonal raider ants shows that it's not that simple, right?

• 15:43Speaker 03

  Yeah, I would say kind of if you wanted to distill these findings down into kind of one main conclusion. It's that basically what the study shows is that there are genes that affect the body size of an individual and therefore the cast phenotype. And then there are genes that affect the relationship between the cast phenotype and the body size. There's basically two different ways to be a queen, right? One is to be larger and one is to have a genotype where queen development sets on at smaller body sizes.

• 16:15Flora Lichtman?

  And when does this queen program initiate? Like, is it when they're in the larval stage, after they've hatched? I mean, when do they know that they're big enough to be queen-like?

• 16:27Speaker 03

  That's a very good question, and I think there we still have to do a lot of work. There are some ant species where it's determined very, very early during development. You can almost tell at the egg stage.

• 16:39Flora Lichtman?

  Oh, wow.

• 16:40Speaker 03

  And then there's other ant species where it's probably determined pretty late during the larval stage, right? And it's, it really only becomes clear once the larva enters pupation, basically metamorphosis. So there's a lot of diversity in ants, I think. And that's going to be very interesting to to study more carefully at the developmental level and at the molecular level.

• 17:00Flora Lichtman?

  I mean, is it good to be the queen? Would you want that if you were an ant?

• 17:06Speaker 03

  So, yeah, exactly, right? Like, you, you think of the queen as the one individual in the colony that has all the power. But in ants, that's not really true, right? Like, the queen is basically this individual that just lays eggs and doesn't do much else. I don't know.

• 17:23Flora Lichtman?

  That sounds horrible, actually.

• 17:25Speaker 03

  Exactly. It's almost like an egg-laying machine or something. So, so I, I, I wouldn't, you know, I, I don't know if I would want to be an ant queen.

• 17:33Flora Lichtman?

  So I was reading that this is a hot topic in the ant world.

• 17:37Speaker 03

  Yeah.

• 17:38Flora Lichtman?

  Tell me why. What's the drama around this?

• 17:42Speaker 03

  Well, I think it's just a very interesting question, right? It's this extreme case of what people call phenotypic plasticity, right? A lot of developmental biology, evolutionary biology is about this question of what's classically discussed as nature versus nurture, right? Like, how much of your existence or your phenotype, the way you are, is determined by the genes you inherited? And how much is determined by the environment you've experienced, right? Or maybe even chance events? And that's a, it's a really interesting and important question. And I think ants are just very, very well-suited to, to address those questions.

• 18:21Flora Lichtman?

  Daniel, thanks for talking to me today.

• 18:23Speaker 03

  Thank you so much for having me.

• 18:30Flora Lichtman?

  Thanks for listening. Don't forget to rate and review us wherever you listen. It really does help us get the word out and get the show in front of new listeners.

• 18:40Flora Lichtman?

  Today's episode was produced by Charles Burquist. I'm Flor Lake Man. Thanks for listening.