Moth Survival Strategies And A Rodent Thumbnail Mystery

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spk_0 I'm Flora Lichtman and you're listening to Science Friday.

spk_0 Today in the podcast from Wing Tints to Tonells, how evolutionary success is in the details.

spk_0 We've found that the answer was very complicated more than we thought.

spk_0 If you are a moth trying to stay un-eaten, there are competing strategies around camouflage.

spk_0 Some moths try to blend in. They're drab. They go for earth tones. Other moths take the opposite

spk_0 approach. They're bold and bright with colors that send the message, don't eat me. I'm poison.

spk_0 I swear. But which one of these winged wardrobes works better?

spk_0 Writing in the Journal Science researchers report on a study that involved placing

spk_0 about 15,000 fake paper moths in forests around the world to see what they could deduce about

spk_0 coloration. Here to talk about it is study author Dr. Ilyana Medina. She's a senior lecturer in

spk_0 biosciences at the University of Melbourne. Ilyana, welcome to Science Friday.

spk_0 Hi, Flora. Very nice to be here. We got to start in the methods today.

spk_0 15,000 origami moths. Please talk me through how you did it and why you did it.

spk_0 Yes. So 15,000 moths could only have been done by lots and lots of people. It was a very,

spk_0 very big coloration and tons of hours of work by many, many other researchers.

spk_0 And yeah, this couldn't have happened without them, really. So yeah, we had teams

spk_0 essentially in all the 21 locations that were placing around 700 of those moths in each of those

spk_0 locations. Still a lot of moths, I would say. 700 to be responsible for 700 moths. That's a lot.

spk_0 Please walk me through the logistics and tell me what they look like.

spk_0 So they are very basic triangles made out of paper, really. We have three different types of

spk_0 targets. So we have a black and orange one that's meant to represent the classic warning colors

spk_0 that we see in nature the most common ones. Then we have a black and sort of gray blue,

spk_0 which is an uncommon type of warning color, but that it's equally bright and equally contrasting

spk_0 as the orange one. And then we have a cryptic type of target that is essentially a brown that

spk_0 blends in really well with most of the bark of the trees around the world. And by cryptic

spk_0 you mean camouflage? Yes, exactly. Yes. I mean camouflage. So a color that blends in really well

spk_0 with backgrounds. And then we baited these paper moths with a mealworm, essentially to test

spk_0 whether predators were interested in attacking this particular target or not.

spk_0 Could the origami moths pass for real moths? Did that matter? Yes, that's a very good question.

spk_0 So we went with this experiment because we knew that it worked before. So there's been

spk_0 smaller, more localized trials of this sort of experimental design before. So we knew that the

spk_0 birds would be attracted to those moths. And the truth is that a lot of animals don't have the

spk_0 great visual acuity that we have as humans. So they would need to be very, very close to something

spk_0 to actually tell that it's not a real moth. Okay, what was the question you were trying to answer

spk_0 here? We were trying to answer under which conditions each of those two strategies would be

spk_0 favored in nature. So as you mentioned, those two strategies being hidden, camouflaged,

spk_0 or being warningly colored, they have evolved many times in snakes, in amphibians, in moths,

spk_0 even in newly-brunks. So we were interested in understanding, yeah, under which conditions

spk_0 which of those strategies would be favored? What did you find? We found that the answer was very

spk_0 complicated more than we thought. So it's always. So the first thing we found that there was no

spk_0 overall best strategy. So the success of each of those strategies completely depends on the context

spk_0 and the type of environment in which the strategy is happening. The other thing we found is that

spk_0 predators play a very big role in determining which strategy works best. And essentially,

spk_0 one of the cool things that we found was that, but the intensity of these interactions and how

spk_0 much prolation there is in a forest really affects how likely predators are to go for those

spk_0 warningly colored moths. And essentially just bypass any fence and just go for it and be pushed

spk_0 by competition to try those things that otherwise they wouldn't normally try.

spk_0 So if you're a bird and you're living in a place where there's lots of other birds competing

spk_0 with you for dinner, you're more likely to try the brightly colored warning sign moths.

spk_0 Exactly. Yeah, yeah, that's what we think is happening. Competition would push these predators to

spk_0 try anything essentially. I mean, are some birds bigger risk-takers than others?

spk_0 Yeah, that's hard to say. I think there's a lot of variation and there's a lot of differences

spk_0 in boldness between birds, but there's definitely some birds that have higher cognitive

spk_0 abilities, like raven, and things like that, that would probably behave differently from

spk_0 something much smaller. How did the camouflage moths fare? Did you learn anything about that strategy?

spk_0 Yeah, so we found that the camouflage strategy, this success was highly dependent on the context and

spk_0 things like the illumination. So forests that have very high light levels that were very bright

spk_0 those forests that camouflage strategy would do worse. And it would also be affected by how common

spk_0 that type of camouflage prey is in a forest. So essentially, if it was forest where the predators

spk_0 were very used to seeing lots of other camouflage prey, then they would do worse. And we think

spk_0 that happens because predators can form search images and essentially get really good at finding

spk_0 a specific type of prey, even if they are camouflage. Some of the moths in your study were this

spk_0 vibrant kind of unnatural blue color. How did they fare where the birds freaked out by them?

spk_0 Yeah, that was an interesting finding as well. So we used that blue black color mainly because it is

spk_0 rare, as you say. So in nature, not many species have that particular combination to advertise that they

spk_0 are toxic or just distasteful. That's quite rare. And then what we found is that that familiarity

spk_0 with the colors matters. So those type of prey did actually poorly in places where the predators were

spk_0 used to the common red and black and orange and black warning signals. If there were lots of those

spk_0 signals or butterflies with those types of colors in a community, then the moths with this

spk_0 and common pattern, the blue and black would do worse. So familiarity with the signal is important.

spk_0 And that helps us understand really why so many species use exactly the same colors across the

spk_0 world and across communities. Those colors work well. And if they are really exposed to then

spk_0 the prey is going to do better because predators are already trained to avoid it.

spk_0 That's interesting. Do you feel like this is the definitive moth coloration experiment like we're

spk_0 done? No, I don't think that really ever happens in science. But I think it was, you know, it teaches

spk_0 lots of things just that, you know, trying to compare different factors in the same study and

spk_0 trying to understand how all those factors interact that brings us closer to understanding how

spk_0 that happens, which is impossible to do, you know, with the smaller scale studies. And just the power

spk_0 collaboration, too, which is knowing that we can, you know, do things like this because there's

spk_0 lots of researchers around the world that I'd think were sent and keen to participate.

spk_0 Yeah, how many countries were you in? I think we were in this was in 16 different countries

spk_0 and 21 locations. Amazing. Do you think the results generalizable to other creatures beyond moths?

spk_0 You know, snakes or frogs? Yeah, I think so. I mean, some aspects of it. So, you know, things like

spk_0 the light, the effect of the light on the camouflage that is something that had been already

spk_0 been sort of found in different smaller scale studies. And then I think that definitely would

spk_0 apply to a lot of other animals that use camouflage as a strategy. And yeah, like certain things,

spk_0 I think that are related to the learning of predators, I would apply again to other types of

spk_0 animals. Yeah, so I think that there's generalizations, but there's also differences in things to

spk_0 consider when we think about expanding our conclusions to other groups. So other other taxa, you know,

spk_0 might use their colors for different types of things as well, not only as an antipriatur defense. So

spk_0 that's important to consider. Helena, thank you so much for joining me today. No worries. Thank you so

spk_0 much for the questions. Very happy to chat. Dr. Iliana Medina is a senior lecturer in biosciences at

spk_0 the University of Melbourne. Don't go away because after the break, we take a look at your nails.

spk_0 We're actually the thumbnails of the rodent mirrored to you. If you show a hand of a rodent,

spk_0 most people they would not guess who's a rodent hand. Stick around.

spk_0 Welcome to decoding women's health. I'm Dr. Elizabeth Pointer, chair of Women's Health and

spk_0 Gynecology at the Aetria Health Institute in New York City. I'll be talking to top researchers

spk_0 and clinicians and bringing vital information about midlife women's health directly to you.

spk_0 A hundred percent of women go through menopause, even if it's natural why should we suffer through it?

spk_0 Listen to decoding women's health with Dr. Elizabeth Pointer wherever you get your podcasts.

spk_0 You hear a lot about a superpower of primates, the opposable thumb. It helps us grip and grasp and

spk_0 hold. But it turns out that among rodents, the special appendage upgrade is slightly different.

spk_0 I give you the thumbnail. Researchers dug into the science of the thumbnail and argue that in part,

spk_0 it's what helped make rodents so successful. Joining me now to talk about it are two authors of

spk_0 that paper. Anderson Fajot is a mammal curator at the Field Museum in Chicago and Raphaela Missagia

spk_0 is an assistant professor at the University of South Paulo in Brazil. Welcome to both to Science

spk_0 Friday. Thank you for having us. Yeah, thank you. Okay, why would you want a thumbnail instead of a claw?

spk_0 Yeah, sure. Basically a nail allows you to have a more dexterity in your in the finger that

spk_0 have the nails. So by the claw would grow over your fingertips and we're kind of getting away.

spk_0 So by having a nail you have more space to have a very high dexterity on those fingers. So that's

spk_0 why, for example, primates are so good at using tools. Among other things, we believe their nails

spk_0 were an important factor on allowed them to have a very good dexterity and handling.

spk_0 I just wanted to add a tip of our fingers and rodents fingers are very vascularized. So they are

spk_0 very useful for tactile sense. They are not opposable but they use in a way to manipulate food.

spk_0 So they are not opposable as primates but they do have this combination of two terms to be able

spk_0 to do the manipulation. What's the evidence for thumbnails being the secret sauce for rodents?

spk_0 I mean, is this an evolutionary history story?

spk_0 Yeah, so another big final of your study was that nails on rodents thumbs are actually

spk_0 very ancestral state and we found a very high confidence that the ancestral going back 55

spk_0 millions ago already had nails on their tongue. So for us, that shows that thumbnails were present

spk_0 across most of the rodent evolutionary history. One of the reasons to explain how rodents become

spk_0 so successful and one of the most common mammals in the world was because they were able to

spk_0 utilize and consume seeds and nuts and this is a very hard resource to access. If you think

spk_0 about like an acorn or another kind of nuts, it's a very hard shell outside that basically

spk_0 prevent other animals to consume it but rodents were able to access this resource and before

spk_0 basically the specialized teeth were the main factors associated with that ability to access those

spk_0 foods. But we're now saying that in addition to have a special teeth specialized muscles,

spk_0 the ability to hold their food with their thumbs and in that case, the thumbnails plays a key

spk_0 role and allowed them to have this dexterity. It's another key piece of the puzzle to explain how

spk_0 they are able to access those resources and because of that evolve in different groups in different

spk_0 environments. I'm thinking of Darwin's beaks. You know, this is just a variation. This is another

spk_0 tool that they use that they're sort of an adaptation to get at the food they need.

spk_0 Yes, exactly. It's a pretty much a similar scenario. Do all rodents have thumbnails?

spk_0 So we found that approximately 85, 86% of species that we analyze have nails,

spk_0 which is a big portion of rodent diversity. But the interesting thing is that most of them have

spk_0 nails and dill food manipulation. That's as Anderson said, it's an ancestral condition, most rodents

spk_0 or like that. But we have some exceptions that appear many times. So one of the exceptions is that

spk_0 we have rodents that don't have anything at all. They don't have nail or claw. So they don't handle

spk_0 food. They eat orally just as cows. One example is the capybara. Right, they graze. Yeah, exactly.

spk_0 So that's a good evidence of a functional relation between the thumbnails and being able to handle

spk_0 our claws just longer nails are they their own thing. They're not the same thing. So claws and

spk_0 nails are basically made of keratin. But they develop differently, at least as far as we know.

spk_0 And for example, even the bone underneath have a different structure to support either the claws

spk_0 or the nail. So like to make clear claws not just long nails. They are different. They have a

spk_0 different composition. Raphael, I'm going to ask you this. Do you feel like thumbnails are kind of

spk_0 overlooked? I mean, they're this tiny appendage. I don't think we give them much thought. What's

spk_0 the bigger story about about this? The thing is four mammals in general and as evolutionary biologist,

spk_0 we tend to overlook some structures. We have some descriptions like species descriptions that

spk_0 mention the tongue, the presence of a tongue nail in rodents, but they always describe them as

spk_0 vestigial or rudimentary, making the impression that they are like not functional.

spk_0 And that's one of the beautiful things about this study. It can speak for myself that I was studying

spk_0 in schools when we started this project and I never even thought about looking into nails.

spk_0 Do you look at your own thumbnails with more respect now?

spk_0 Yeah, with respect and with more love maybe. I was so surprised when I saw the first

spk_0 features of rodents hands and thumbnails because they are short as our nails.

spk_0 And they really look like a nail. Like if you show a hand of a rodents, most people they would not

spk_0 guess was a rodents hands. Oh my gosh, I know. The pictures which we'll put on our website at

spk_0 sciencewriting.com slash thumbnail are pretty shocking. It's going to be like my iPhone background,

spk_0 you know? Yeah. And for me, before this project, I never thought on rodents thumbnails,

spk_0 but now every time I see a squirrel, it's the first thing that comes to my mind. Like,

spk_0 oh my god, that's amazing. I can only picture the thumbnail in my mind.

spk_0 Thank you both so much for taking time to talk to me today.

spk_0 Yeah, thank you. Thank you for the interest in your study.

spk_0 Yeah, it was a pleasure. Talk to you later.

spk_0 Anderson Fajjo is a mammal curator at the Field Museum in Chicago and Rafael a misogyna

spk_0 is an assistant professor at the University of Sao Paulo in Brazil.

spk_0 Today's episode was produced by Charles Bergquist. I'm Florel Lickman. Thanks for listening.

Moth Survival Strategies And A Rodent Thumbnail Mystery

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