Leap Into the World of Jumping Spiders
Encountering a jumping spider might give some people a start, but researchers are interested in these agile arthropods, especially their ability to plan and execute complex behaviors. Scientists are studying how jumping spiders coordinate their eight eyes to track fast-moving prey, and how these earless animals can pick up noises from across a room.
Arachnologist Paul Shamble discusses the sensory systems of jumping spiders and how scientists go about measuring the small creatures’ neural activity. And ecologist Eric Olson discusses why these predators might enjoy a vegetarian snack now and again.
Paul Shamble is the John Harvard Distinguished Science Fellow at Harvard University in Cambridge, Massachusetts.
Eric Olson is a senior lecturer in Ecology at the Heller School for Social Policy and Management of Brandeis University, in Waltham, Massachusetts.
IRA FLATOW: This is Science Friday. I’m Ira Flatow. Certain animals capture our imagination. Maybe it’s their mastery of mimicry or their ability to blend into their surroundings. Some are able to solve problems that seem too complicated for such a little creature. That description fits an animal I am thinking of. Any guesses?
If you’re thinking the octopus or any of the cephalopod cousins, good guesses. Here’s a hint.
Yes, Spiderman. That’s the great hint, because I’m talking about jumping spiders, the spiders that jump just like Spiderman Man does, who jumps and pounce on his prey. And here to explain and expound is Paul Shamble, a science fellow at Harvard University. He joins us from the studios on the campus there. Welcome to Science Friday.
PAUL SHAMBLE: It’s great to be here. Thank you.
IRA FLATOW: Jumping spiders. I see them crawling around everywhere. They’re like weaving webs and stuff like that. I mean there are jumping spiders that we see them?
PAUL SHAMBLE: Yeah. I know you know typically when I think about spiders we all sort of have this imagination of like the Charlotte’s Web spider right yeah the one that makes the beautiful or webs that live in your backyard and those kinds of things but it turns out there’s this whole other class of spiders these guys that just sort of wander around and they don’t weave capture webs at all. Instead, they have to actually sort of hunt down their prey.
IRA FLATOW: Just like Spiderman. And just jump around on them.
PAUL SHAMBLE: Yeah, exactly. And so jumping spiders are in this category. They’re these guys that are just really, really active predators. I mean that’s what I mean they must have great vision, right, to be able to look around them and jump on their prey.
PAUL SHAMBLE: Yeah, exactly. That’s really their sort of claim to fame. If you see zoomed in photos of them they have these great big enormous eyes and they’re sort of one of the premier examples specialized visual creature.
IRA FLATOW: Can you give us an idea how their eyes work?
PAUL SHAMBLE: Yeah, sure. So it’s absolutely spectacular. So your eye has to sort of do a couple different things. You have a retina in the center that has really, really high resolution vision. And then the rest of your eye the resolution gets worse and worse as you get to the edges.
And so all that is built into one thing, and with spiders, spiders in general have eight eyes. And so for jumping spiders, each eye has become specialized to do a different thing. And so they have a pair of eyes that basically point backwards and tell them if there’s danger coming. They have a pair of eyes that point up and do more or less the same thing. And they have four eyes that point forwards.
And so these two sort of on the outside on the sides that are essentially like your peripheral vision. They are really, really excellent at motion detection and things like that. And then they have these two eyes in the center that are just absolutely amazing. They’re there like a retina. They’re movable.
They have a four-tiered retina, so they have four layers of retina in a row that seems to be capable of calculating in-depth through one eye alone through image defocusing. And they have color vision. Their field of view is like 300 degrees, and they have this visual resolution that is better than lots of vertebrates. Better than toads, better than lizards, all kinds of things.
IRA FLATOW: So they must have their brains must be different than to process all this information?
PAUL SHAMBLE: Yeah. This is one of the things that’s really special about them is that they just seem absolutely awash in information. I mean, they can also perceive vibratory information and they can hear and we now. But all of this goes into a brain that we think has fewer neurons than a fruit fly. And so somehow, they seem to have come up with some way that they can really, really handle just a ton of information.
IRA FLATOW: Now I understand that jumping spiders have been taught some complex behaviors? You can train a spider?
PAUL SHAMBLE: Yeah. They are amazingly intelligent animals. You can do sort of simple things, like if you show them a little video like on your iPhone, they will attack it if they think it’s prey and they’ll leave it alone if they don’t
IRA FLATOW: Oh, come on.
PAUL SHAMBLE: Yeah. And it gets worse– worse, depending on how you think about it. It gets more impressive than that. They can solve 3-D mazes. So if you set up a little thing and you put like a couple sticks on a table or something and you put a fly at the top of one of them, they’ll look at the scene and they can figure out which route they’re going to have to take in order to get to the fly, which seems sort of simple, until you think about how much visual information goes into that decision, like whether you go left to climb that stick or if you go right, and whether the whole maze connects or not. So they’re just really, really amazing creatures.
IRA FLATOW: Yeah. And you hinted at before their ability to hear sounds, but they don’t have ears.
PAUL SHAMBLE: Yeah. So this is some work that I did just recently with Gil Menda and a really wonderful team at Cornell University and Professor Ron Hoy’s lab. And so what it comes down to is that spiders have these sensory hairs.
Like you said, they don’t have ears at all. And so the way that spiders detect what we would call sound. Physics-wise, this gets a little bit confusing, because our ears detect pressure differences, and their hairs detect the actual particle movement. And so when you make a sound both those things happen. But there is the interaction and sort of the connection between them is pretty complex.
So it turns out that we were sort of drastically underestimating the ways in which this worked in sort of the real world.
IRA FLATOW: Wow. How do you test it out?
PAUL SHAMBLE: Very
PAUL SHAMBLE: Very carefully. You know.
IRA FLATOW: My favorite answer.
PAUL SHAMBLE: Yeah, I’m sure. You know, there’s a lot of things that are kind of tricky about working with spiders. They’re so good at detecting vibrations that if you just put a big speaker next to them, you run the risk of just shaking the table. And so you think that they’re hearing it through the air, but really they’re actually feeling it through the ground.
So we sort of had to do a lot of experiments to kind of get around that problem. But really what it comes down to is you put a speaker in a room and in this case, you either observe behavior, or we also did recordings from their brains.
IRA FLATOW: So you walk around the room clapping, does it react? Or go out and bang the door, that kind of thing?
PAUL SHAMBLE: Yeah, you know, that’s how this whole project started. My colleague Gil Menda, we were doing this other paper. And it was about vision. And one day Gil set up an animal to do the recording. And he went to a slightly different part of the brain with the recording. And he squeaked his chair against the ground, and the way the lab is set up you could hear the neurons fire whenever you get neural activity. So he squeaked a chair, and the neurons fired. And he sort of sat there for a second.
IRA FLATOW: Wow.
PAUL SHAMBLE: And he backed the chair up again and it squeaked again. And that was after a sort of afternoon of clapping and being amazed, we then sort of had to go on and turn it into real science.
IRA FLATOW: That squeaky serendipitous moment has to go down as science.
PAUL SHAMBLE: It certainly has in our tiny corner of the world.
IRA FLATOW: We’ve been talking about that jumping spiders and how they’re built to be hunters. But even the biggest meat lover wants a few veggies now and then. Right?
My next guest observed a species of spider taking, well, let’s say a sort of a salad break. Eric Olson is a senior lecturer in ecology at Brandeis University in Waltham, Massachusetts. Welcome to Science Friday.
ERIC OLSON: Hi, Ira. Thanks so much for having me on.
IRA FLATOW: You’re welcome. Tell us about– I understand you were out in the field, and you observed a spider feeding on a plant. Was it munching on the leaves there.
ERIC OLSON: No. So this is another case of serendipity. I got to give a shout out to Earth Watch. You know, the Earth Watch volunteers that come and help scientists in the field? As part of a sort of a side project to my main project in Northwestern Costa Rica I had these volunteers beating with the beating sheets just collecting jumping spiders. They’re beautiful animals. And as Paul was saying, they’re really smart and elegant little critters.
And we had an artist onboard who was helping us make this nice catalog of the jumping spiders. And my volunteers actually brought in a spider we’d never seen before after several years of doing this inventory. And I said, wow, where’d you find that? And they said it was on an ant acacia.
Now, the ant acacia is a tree that’s covered in stinging ants. And the ants help the plant by defending it. And the plant prepares the food for the ants. And all the food of the ant colony comes from the tree. And the really spectacular food are these little yellow pellets on the tips of the new leaves.
And what it turned out after a couple of years of my disbelief, you know, I finally said, OK, this spider keeps turning up on this ant acacia. We’d better go see what the heck it’s doing. And so by observing this spider, we found that it was actually eating these, stealing the ants’ food, the pellets that the plant was making as ant food.
So it is a spectacular example of the behavioral plasticity of these wee little predators that they took to eating plant tissue.
IRA FLATOW: Does that make it easy for them instead of saying, hey, let’s go jump around and find my own food? Let’s just take their food.
ERIC OLSON: Well, it must be the case that it favored this phenomenon. Because now we’ve collected over 1,100 jumping spiders of various species in this park. And we have never found this spider on any other plant except ant acacia. It seems to be a spider with a host plant.
And so you know it’s really a bizarre story. And there’s a lot of unanswered questions still like, how does it get around?
But your question about favoring this behavior, once it’s on the plant, remember the ants keep everybody else off. And so it’s a kind of a safe haven. There’s no other spiders. There’s no praying mantises that might eat a spider. Birds don’t even come to this plant for very long. You know? So it’s like a little paradise bubble with lots of food.
But the ants hate the spider. And they’re always chasing it around. So it’s kind of a blessing and a curse at the same time.
IRA FLATOW: So they can’t gang up on the spider enough to keep it away?
ERIC OLSON: Well, remember, these spiders, as your other guest was saying, their vision is astonishing. So long before the ants see the spider, the spider sees the ants coming and just like hops to the next leaf. And of course, if it really gets cornered, the spiders have a trick up their sleeve, if you will. They can hang from silk. And the ants can look over the edge of a leaf and curse it, but they can’t get at it because it’s hanging there.
IRA FLATOW: It’s a great story. This is an amazing spider. These spiders, can we see them? How do we find them? Now I want to go find them because I’ve seen tiny little spiders crawling around without webs, because as you say, they don’t create a web. Where can we find them?
ERIC OLSON: Well. I’m sure Paul has an answer for that too.
IRA FLATOW: Paul, you want to–
ERIC OLSON: Go ahead.
PAUL SHAMBLE: You know, the place that I always look is actually just on the sides of buildings you can find a lot of jumping spiders just sort of any kind of warm day in the summer, spring, or even into the fall. Because any building where you have a lawn that goes up to a building, just because it makes for this big flat space that’s very easy for them to find prey on. That’s the easy answer.
I’m sure that Eric has a much more impressive tropical answer.
ERIC OLSON: No, I mean tropical or anywhere else, if you’re in a little wooded area or like the margin of a forest where it meets the fields, just take an umbrella and a stick and hold the umbrella upside down and beat the bushes so stuff falls into the umbrella. And you’ll find jumping spiders. They’re hiding away in the foliage and looking for prey.
One little anecdote I love is that the Chinese word for jumping spider is Fly Tiger. So it translates that way into English. So you’ll figure out which ones are jumping spiders pretty easily if you look closely at those eyes.
IRA FLATOW: I’m Ira Flatow. This is Science Friday from PRI, Public Radio International. Talking with Paul Shamble and Eric Olson about these amazing jumping spiders.
Now, Eric, I understand that the jumping spiders like to get up close and personal with aphids. Is that correct?
ERIC OLSON: Well, so there are some other cases of plant feeding by spiders. And this took a lot of us by surprise just how common this is. But my co-author, Martin Nyffeler, from Switzerland, in a paper that he really was the lead author on recently, he did a massive literature review and contacted spiderologists from all around the world. And he collected scores of examples.
And one really quirky one is that spiders will sometimes visit these colonies of aphids that are feeding on plant liquid saps. And sap is a really crummy nutrient-poor food. And so the aphid passes a lot of the liquid through its body, kind of filters out the nitrogen. And it drips this honeydew, basically sugar water out the end of its tail. And the spiders will sometimes imbibe that.
Anyway, it’s a weird visual. But that’s what they’re doing.
IRA FLATOW: They’re drinking juice out of the butt of an aphid is what you’re saying, euphemistically.
ERIC OLSON: Basically– yeah, just plain straight talk, that’s what they’re doing. That’s right.
And and they’ll also visit nectar in the flowers. And on some plants there are even extra floral nectars. They’re really designed, we think, to attract ants. But once again, the jumping spiders will jump in and take that nectar. So these are plant products, nectars, and so on. And spiders are, they’re taking them.
IRA FLATOW: Let me go quickly a question from Chris in Geneva, New York. Hi, Chris.
CHRIS: Hi, Ira. How are you?
IRA FLATOW: Fine. Go ahead.
CHRIS: See, listen, I happen to be lucky enough to have [INAUDIBLE] jumping spiders in my backyard. So these are jumping spiders that try to look like ants.
And the question I have, since they don’t seem to be associated with the ant colonies that are in my backyard, why do they walk around on their six hind legs and pretend to use their front two legs as antennae if they’re not trying to fool the ants? Are they trying to fool wasps who might prey on them?
IRA FLATOW: Good question. I didn’t know they do that, Eric and Paul.
ERIC OLSON: So I’ll try a stab at that one. So ants sting. A lot of ants have a stinger. And not all ants, but a lot of them that jumping spiders mimic are, if a bird grabs it they might get a sting right next to the eye.
So I think in many cases it’s an effort to hide. And some of the ants that they are particularly fond of mimicking are really kind of solitary hunters. And so, yeah, I don’t really think they’re trying to fool the ants.
There are some jumping spiders that eat ants. It’s not unheard of.
IRA FLATOW: But why are they trying to mimic an ant then?
PAUL SHAMBLE: Well, OK if I take stab?
IRA FLATOW: Yeah, go ahead. I’ve got about a minute left. Go ahead.
PAUL SHAMBLE: Sure. So this is actually– this was the other half of my Ph.D. Thesis at Cornell.
ERIC OLSON: Oh, so you should have taken that one.
PAUL SHAMBLE: I’m not surprised that you have these out there in Geneva. There are a couple different species of jumping spiders, even just in upstate New York and sort of the northeast that do this. And just like Eric explained, it seems like, especially in these cases, it is a case of what’s called Batesian mimicry. It’s that if you’re a generalist predator out there and you just want to eat little tiny bugs, you tend to really not want to eat ants because they taste terrible. They have angry friends. They sting. They bite.
And spiders are delicious. So if you can fool everybody, then there you go.
IRA FLATOW: Great lessons on jumping spiders. This is a weekend project for all of us. Thank you, Paul Shamble, a John Harvard distinguished science fellow at Harvard and Eric Olson, senior lecturer in ecology at Brandeis in Massachusetts. We’re going to take a break and talk about a new drug test about possibly narrowing down what calls us Alzheimer’s. Stay with us. We’ll be right.