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Hello, SHORT WAVErs. It's Maria Godoy here. The sight of spiders makes a lot of people jump. I was once in a parked car with a friend who hit the gas and drove into a parking meter in front of her because she panicked after she saw a teeny tiny spider in her car. But Daniela Roessler loves spiders.
DANIELA ROESSLER: All spiders are pretty fascinating from a biological and ecological standpoint, so there really is no reason to be afraid of any spider. But in particular, jumping spiders are absolutely amazing because they have this incredible eyesight, so they have really, really good eyes. And they can see almost as good as we do. So they have - they pay attention to detail. They're really great at hunting. They basically hunt like little cats.
GODOY: She says they love to hunt mosquitoes for one thing, which is pretty helpful for us humans.
ROESSLER: Generally, spiders in every ecosystem are really top predators in the tiny world. So they do eat a lot of things like small bugs and other spiders and insects. So especially jumping spiders, they usually - you would often find them preying on something that is just as large as they are.
GODOY: They're not afraid to take on the big guys. OK (laughter).
ROESSLER: No, they're absolutely not. But that's the thing. They're usually always seen as the predators and less so as prey.
GODOY: And she says, these jumping spiders - they're called salticids, by the way - they're active during the day unlike a lot of spiders that weave webs, so their eyesight is particularly important.
ROESSLER: So you have eight eyes, so four pairs of eyes. And from the front, you can see the big frontal eyes and then the secondary eyes that are a little bit smaller right next to those. So those secondary eyes they use for motion perception. So everything that moves gets processed through those secondary eyes and the big frontal eyes, they're really, really amazing.
GODOY: These days, Daniela is a researcher with the University of Konstanz and the Max Planck Institute of Animal Behavior. But in 2020, she was in Paul Shamble's lab at Harvard University, and she decided to check out what happened when one of these jumping spiders with their amazing eyes encounters a possible predator. Today on the show, just in time for all those scary Halloween decorations, we talked to Daniela about what scares spiders. Turns out, arachnids can have arachnophobia.
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GODOY: Daniela, tell me about why jumping spiders are such a good animal to study, especially for this experiment.
ROESSLER: Well, first of all, it's really easy to go outside and just catch them, which is just great, especially because I used to work on frogs from the Brazilian Amazon, and nothing about that was easy - absolutely nothing. They're also great for these behavioral experiments because you can really see what they're doing, and you almost feel like you can see them thinking and making decisions.
GODOY: Interesting. And they're smart little creatures.
ROESSLER: Yes, exactly. They're very smart.
GODOY: One thing you talked about in your paper and your presentation on this experiment is that these spiders, we think of them as predators, but they can also be prey.
ROESSLER: Exactly, yes. And they become prey to other jumping spiders. So we regularly see this in the field. Or if you run out of vials in the field and you think, oh, I just put those two spiders together, you usually end up just having one.
GODOY: So they're cannibal spider cats. Got it.
GODOY: OK. So what was the goal of this experiment? What were you trying to find out?
ROESSLER: It kind of came about by accident (laughter).
ROESSLER: I started my postdoc at Harvard, and they already started trying to make really nice, detailed 3D prints of spiders that are based on CT scans. So I printed the salticid that we ended up using in these experiments and just put it in front of a spider more or less for fun to see, OK, what would happen.
And that's how we observed this extremely robust behavior, that they would just immediately look at it and just back off and run away. It was just fascinating and we really wanted to find out more. And what are the triggers? What are they paying attention to?
GODOY: So walk us through this, you know, interesting little spider experiment.
ROESSLER: OK, so the spider would be introduced to a little tiny start platform where it cannot really jump away from. Then there is a little gap of 1.5 centimeters towards another platform, and that's where we placed different objects to kind of forced them to look at the object. And once they look at the object, they have to make a decision - do I jump across or not? And even after they jump, there's another decision of whether or not they would pass the object.
GODOY: Can you tell us what it was that you used? If I'm correct, you used a control that was just, like, a little black 3D-printed sphere.
ROESSLER: Yes, exactly.
GODOY: And then you use dead spiders, like, big, old, jumping spiders that are known predators, right?
ROESSLER: Yes, because we wanted to know if this behavior that we saw, this backward running away, if this was something that they just do for this 3D print or whether that - we actually created with the print something that resembles an actual predator. So we tested a large predator that co-occurs naturally with the spiders we tested. And we also tested a larger predator that they should have never, ever seen and encountered in their life to get an understanding of whether experience has anything to do with the recognition or not.
GODOY: Well - so describe what happened. What did you find out when they face these big, hairy, kind of kind of icky - I know you love them but, sorry, they're not so attractive to me - spiders, these big spiders? What did our jumping spider hero do?
ROESSLER: (Laughter) So amazingly, when they saw the jumping spider that our 3D print was based on and they should have never seen before, they showed the exact same behavior. So they saw it and really quickly, they - so the moment when they see it is when they stop walking. They can see it, so they freeze. They don't move anymore. They look at it, and then within a couple seconds, they run away.
ROESSLER: And so we found the exact same behavior that we found towards the 3D print, and that was absolutely amazing. And they didn't do that for the control. So they were not afraid of a similar-sized object. So it was something about the spider-ness really freaks them out.
GODOY: Yeah. I watched the videos you made of these experiments, and the spiders did seem to be way more afraid of the 3D models with eyes. I wonder if my friend who hit the parking meter would be comforted by this.
GODOY: You know, spiders are scared of themselves, too.
ROESSLER: Yes. I think yes. I think we're giving people with arachnophobia a really good reason to connect with them because now people have something in common. Like, no matter how much you hate them, now you have something in common.
GODOY: (Laughter) I'm going to get in touch with my inner spider here.
GODOY: So I wonder, you know, why do you think the jumping spiders' reaction were so much stronger in some cases than others? Like, at one point, the spider is sort of backing away slowly. Like, you can see it may be trying not to catch the attention of the predator spider.
GODOY: And then sometimes, they move super quickly. Like, scram, I got to get out of here. Like, they're definitely scared.
ROESSLER: That's a really good question. It is quite possible that there's a lot of assessment of the risk in this moment. So they assess, how big is that thing? How quick could it get to me? And then also knowing that motion really, really triggers what jumping spiders perceive - like, moving away in this kind of choppy fashion and really slowly maybe is also a strategy of not getting the attention from the predator.
GODOY: So when they freeze, that's because they may be more aware it could be a predator, and they're assessing what to do, which is kind of funny because that's maybe what I would do if I - I don't know - encountered a mountain lion or something.
ROESSLER: Yes, exactly. It's the same.
ROESSLER: I mean, it - this is really about survival, so yes.
GODOY: OK, OK. I am connecting with the spiders now, I have to say. So these spiders, we've talked about the fact that we need them around - right? - to keep the mosquitoes away, which is very important, among other things. That has me thinking. Is it bad to put out fake spiders on Halloween? Like, what will it do to the real ones?
GODOY: Are we hurting them?
ROESSLER: Aw. Well, yeah, maybe we're traumatizing - I have been asking myself if I've been traumatizing those spiders in my experiments because there is actually...
GODOY: (Laughter) I know.
ROESSLER: There is such a thing as the ecology of fear and how surviving a predator attack makes animals, like, more vigilant afterwards. And they actually...
ROESSLER: ...Change their behavior, pretty much like PTSD. So...
GODOY: Wow, really?
ROESSLER: I'm mildly worried. Yes, yes. Of course, we do not know that for spiders. Like, all of this research is very vertebrate heavy. That's - yeah - one of the many reasons why the findings of our research are so incredible. Because all of these cognitive abilities and perceptual abilities that are so nuanced, they're - it's really surprising for an invertebrate to be able to do these things.
GODOY: I'm a little worried my whole neighborhood is a trauma zone at this point because there's, like, giant spiders out everywhere.
ROESSLER: (Laughter) I mean, I guess...
GODOY: We really get into Halloween.
ROESSLER: Spiders that are being placed out are really, really big. And also, I guess spiders for Halloween, those are usually those spiders that build webs. And one thing that we also found is that the eyes are very important. And...
GODOY: Oh, OK.
ROESSLER: As those web spiders don't really have very conspicuous round eyes, I might say they would not trigger the same behavior.
GODOY: OK, good. All right, so we're safe. We're safe because as long as their eyes aren't very realistic - they're not the big googly eyes.
ROESSLER: Yeah, I think there's a thing about being looked at. And usually, all predators have forward-facing eyes. And...
ROESSLER: It's a thing we see repeatedly in nature that is being exploited. Like, butterflies that have these eye spots. Like, eyes are - yeah, eyes are scary. Being looked at is scary.
GODOY: All right, Daniela. So you clearly love spiders. And it's amazing to watch them, but why study jumping spider cognition? Are there other applications for this research?
ROESSLER: To me, it's mostly about, like, proving people wrong (laughter).
ROESSLER: Like, we're in a - such an anthropocentric place. We always feel like research has to be for the greater good of us humans. And we think that the cognitively hard things can only be achieved by us with large brains or mammals with large brains, primates. But we don't expect these things to be present in things that have a brain the size of a poppy seed. So to me...
ROESSLER: ...It's absolutely fascinating to show what they're able to do and what they're capable of.
GODOY: Daniela, thank you so much for your time. This has been really, truly a fascinating conversation. A lot of fun. Yeah, and just in time for Halloween. I am going to have to rethink those decorations; check the eyes out to make sure they're perfectly fake looking (laughter).
ROESSLER: Yes (laughter).
GODOY: They don't look anything like the real thing so as not to traumatize my newfound spider friends.
ROESSLER: (Laughter) Exactly.
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GODOY: Daniela's research appears in the journal Functional Ecology. We'll have a link to her paper and the video of the spider experiment in the episode notes.
This episode was produced by Eva Tesfaye and edited by Gisele Grayson. Margaret Cirino checked the facts. Patrick Murray was our audio engineer. Thanks for listening to SHORT WAVE, the daily science podcast from NPR. I'm Maria Godoy. (Speaking Spanish). Goodbye for now.
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