Lizard Push-ups and Jumping Spiders

Dr. Biology:

This is Ask A Biologist a program about the living world. And I'm Dr. Biology. In this show, we're continuing our series from the SICB Conference held in January. We were a guest of the Spatial-temporal Dynamics and Animal Communications group. They let us set up a remote studio close to the action. 

And speaking of action, it's amazing what some animals do to attract a mate or tell a competitor, go away. There are lizards who display bright colors and do push-ups to both attract a mate while telling other males to stay out of their space. There are even more colorful animals who show off a wide range of colors and turn to dance to find a partner. Here we're talking about jumping spiders, and they are pretty amazing dancers considering they have eight legs. 

My guest scientist has been studying both lizards and spiders. David Clark is a scientist and professor at Alma College. He's researching animal communication and the evolution of visual display. His work with Lizards was featured in the 3D documentary on the Galapagos Islands that was narrated by naturalist Sir David Attenborough. It turns out that David, David Clark, is also a moviemaker. But in this case, his audience has been mainly his jumping spiders. You know, come to think of it, I'm wondering what his reviews are like from his moviegoers. Let's head over to the conference to see if we can find out. 

Welcome to Ask a Biologist, David.

David:

Well, thank you for having me. I really appreciate this.

Dr. Biology:

Your work is with two very popular animals, especially if you live in the southwest. One is lizards.

David:

Mm hmm.

Dr. Biology:

And the other one we'll get into later on. But for now, let's talk about your lizards. What is the lizard that you work with?

David:

I've worked with a couple of different species of lizards, the Anolis lizards. I've worked with anoles, [which] are quite abundant throughout the Caribbean and into South and Central America, where you get the greatest diversity of these anoles. We probably know them here in the United States as like the American Chameleon. 

They're not really a chameleon, but they do change color. They're relatively small and slender lizard and they have a unique kind of throat fan that is often very brightly colored. And they might use that for species recognition so that they can recognize a member of their own species when they start to display, or they may use it when they're courting a female, or they may use it during territorial displays where males are trying to shoo other males out of their areas. In addition to the very bright colored throat flap that they have. 

They also do these unique kind of displays called push-up displays or head bobbing displays. They go by a variety of different names. But these displays can be seen from quite some distance away, and often they have a unique pattern associated with them. And we sometimes think of this as the language of the lizard, because each lizard species has its own unique display that it does when they bobbed their head up and down, and then they throw that little fan, that little colored fan into the mix.

Dr. Biology:

Right. Is it the dewlap? Do we call it the dewlap?

Dr. Biology:

Yeah. Yeah. That's the scientific term. And we talk about color. A lot of people will think of chameleons that change their colors at will, you know, pretty quickly.

David:

Right.

Dr. Biology:

These lizards do they change their dewlap color very quickly or is this something mainly when they're out, for example, looking for a mate?

David:

Well, that's an interesting question. The dewlap color does not actually change. It's the body color that changes in these. And they often will do that when they're on a dark background. Their body will become very dark. In order to blend into the background. They show what we call crypsis, you know, where they are trying to camouflage themselves against the background or if they're on a light-colored background, their body may be light in coloration. So they can do that. They're not as good as some of the old-world chameleons. That can really change to quite radical colors, such as bright yellows and reds and blues, but they're pretty good at it.

Dr. Biology:

You call it the language of these lizards. Let's talk about this language because, you know, we're talking about color. We're talking about also actually movement, too. Because they are doing these push-ups and how that is used for their communication because I suspect it's not always just one thing they're trying to communicate

David:

Probably not. Oftentimes, particularly in some of these lizards that we've been studying, the display can serve kind of multiple purposes if the male is patrolling his territory and sort of setting the boundaries of his territory by displaying at the edges of it, he may be broadcasting a signal to other males to tell them to stay away. If at the same time that same signal may be picked up by a female and she would interpret that signal very differently.

She may be much more likely to interpret that as a male that's calling to her or that displaying for her. And then she has to make a choice is this a good male to mate with? Is this a male that I don't want to mate with it on that particular day?

Dr. Biology:

Oh. So, in this case, it works nice, has dual purpose.

David:

It is a dual-purpose display. Yes.

Dr. Biology:

Right.

David:

Yeah.

Dr. Biology:

And you know, you said they patrol their area. You know, basically, they say, you know, this is my space. Other males stay away. And then for the females, they're saying, take a look at me.

David:

Right.

Dr. Biology:

I might be a really good mate for you. How big of an area are we talking about?

David:

That varies considerably depending on the species in some species. The area may be actually quite small, just a few meters in size. In others that size, maybe 30 or more meters in which a male has jurisdiction in that particular area. Now, oftentimes these males will have multiple females within the territory and females are likely to set up their own territories within that male's territory. So, you have sort of these little sub territories and females then will vie for their position and display to other females to keep them out of their little area within these territories.

Dr. Biology:

Now, are the colors on the dewlaps only on the males?

David:

Only on the males. Now we can talk about another species of lizard that I've been studying in the Galapagos Islands where the males really don't have a dewlap there. They do have some throat coloration, but there is no fan or dewlap or anything like that. But the females in this case happen to be the ones that are very brightly colored.

Dr. Biology:

Hmm. 

David:

So, a little bit different.

Dr. Biology:

What are these lizards that are in the Galapagos that you're studying?

David:

These are called lava lizards. There’re the lizards in the Galapagos Islands. They're related to a species of lizards that's found on mainland South America in Ecuador, but in the Galapagos Islands, each of the islands. And there are about nine different species of these lizards that live out there. And no two lizards that live on the same island. Each island has its own unique species of lizard that lives there. So, this makes for a really kind of unique opportunity to begin to study some questions about species recognition and the evolution of these sorts of displays as kind of a natural experiment. That's happened out in the Galapagos.

Dr. Biology:

Right. The Galapagos is really a very popular destination for scientists and for tourists. And that's both good and bad because we're really working hard. And I know that the country of Ecuador is working really hard to protect that area.

00;08;18;10 - 00;08;18;29

David:

Absolutely.

Dr. Biology:

So, some people, if they've thought of the Galapagos, they'll think about the finches, Darwin's finches at the Galapagos. But the lizards, the lizards have a really important story to tell as well. So, pardon the pun, but let's learn the tale of these lizards.

David:

All right. Well, I've been studying these lizards in the Galapagos for almost 12 years now. And originally I was interested in things sort of like what their coloration was all about. How well do they blend into their background? Are there any species that show particularly bright coloration compared to others, that kind of thing? And the sorts of displays. 

Now originally the displays for these lizards was described in the 1960s and each of the different species of these have a unique display pattern associated with them. And that's sort of what got us interested in beginning to study these lizards using robots so that we could begin to control really what the lizard looks like because our model can look like something we can make it look like whatever we want and we can also make it behave in a way that we want it to behave. And so, we can mix and match what they look like and what they behave like. 

And so that led us to beginning to answer or ask, I guess, some questions about species recognition. Do the lizards from the different islands? If you were to show them a lizard that they haven't evolved with, could they recognize that display or do they just ignore it? What do they do when they see a lizard from a different island displaying to them? 

You mentioned also the fact that in the Galapagos you have to be very careful about manipulating the animals that are there, and there are many rules about doing that sort of thing. So, you can't just go into the field in the Galapagos and paint a live lizard, but you can do that to a robot without any problems or anything like that. And so that makes these robotic models or another kind of model. You mean you can paint them or anything like that, but with the robot, you get the addition of a correct behavior pattern associated with the looks of the animal as well. And so, with them, you can do what you want to.

Dr. Biology:

Right. So, what do you make your robots out of?

David:

That's a great question. The original robots were actually made out of a wooden kind of skeleton. I took a dowel, basically a wooden dowel, and shaped it into the form of a lizard. And then from that used a photograph of a side-long lizard, taking it from a sideways view, and made what I call a digital skin that was prepared in Photoshop. And then that was printed so that it looked like a real lizard. That was then from the photograph, it was stretched over the little wooden dowel. Then I used servo motors to control the bobbing display of the lizard, my brother, who is a physics person and interested in engineering and that was also very interested in radio control sorts of things like airplanes and cars and that sort of stuff. And that got me really interested in the use of the servo motors for controlling some of these little robots like that. 

And so, in using these small motors to control the robot, you can control the display now getting them to do that. I'm not a programmer, I'm not a computer programmer. So, I needed a way in which I could actually get them to display appropriately. And interestingly, I connected with our music department at Alma College. Because MIDI, as it turns out - MIDI is a very commonly used in a lot of different things, like your little music that probably comes out of your phone there, make a ring tone or thing. Something like that is probably some sort of a MIDI program that that does that. It turns out MIDI, you can actually construct the programming and they're using a visual kind of way of doing it graphically. 

And so, because the displays had already been worked out for these lizards, I could then replicate the display within the computer program that really replicated the display pattern of the lizard. But in fact, it was actually MIDI controlled and I had to use a little iPod in the field to control it. So, it was playing through this little music program that would then control the up and down behavior of the Lizards body as it displayed.

Dr. Biology:

This is another great example of where science and art, they are just kindred spirits and it's great that you're looking for your solution. You're not a programmer you end up going to the music department. You learn about MIDI, and you start to use that in your research. Did you get any of the music faculty involved with this?

David:

I did, yes. Yeah. Ray Riley was a music professor at Alma College, and he got involved with helping me learn how to use the MIDI program that we use to do the displays.

Dr. Biology:

I've always wondered because some of our scientists, especially the some of our younger scientists, are also taking some of the information, the data they're collecting, and they're actually presenting it back in a more artful way. I find it really intriguing how the world of science and art, they're such kindred spirits. And so, there are times where the scientists are pulling in materials. In this case, are our tools the MIDI tool for your work with your robotic lizard. Did the faculty, or did anyone have an interest in taking recorded behaviors of the lizards, the real lizards, and composing music basically off of that?

David:

That's a great idea. We just never did that. We didn't do that kind of thing with it. That would be really pretty neat to do because something there's so much variation in the display patterns. In more recent years, I have now switched from using MIDI because it was a bit more cumbersome to use in the field because you had to have an iPod associated with it to be able to play that and so you had the extra pieces of equipment out in the field.

David:

And when you're in the field, a lot of times you have to streamline things because you never know when things are going to go bad. And so, in more recently, we've switched over to Arduino boards, and probably many of the students listening are familiar with Arduino, and it's a relatively simple way to program and control many different devices all the way from Bluetooth devices to these little servos.

David:

And in addition to using these Arduino boards, we've also now gone from what I think of now is relatively crude-looking models that I had used earlier to using 3D printing and 3D printing models of the lizards so that we get really quite accurate looking lizards. I mean, they look very lifelike.

Dr. Biology:

Right. A quick question for me is how do you get the information? How do you get the three-dimensional information into the computer to create the three-dimensional models?

David:

Well, these are scanned in using 3D scanning software to do that. You can also find many people have uploaded various models onto the Internet, and so you can download them and then manipulate those models in your own software that you might have on your desktop. And begin to change the morphology such that it looks like the lizard that you're trying to replicate.

Dr. Biology:

Right. I was going to say I would be real surprised if your lizard was out there already online, even though there's an amazing amount of things out there. But this way you could change the actual shape and make it look exactly like they're supposed to. All right. So, here we are. You've created your world of robotic lizards What have we learned? 

David:

What have we learned from that? Well, what we have been looking at, we've done some things with species recognition. What we found is that some of the lizards on the different islands, some of them are very good at discriminating their display from that of another species. We call them discriminator because they can discriminate.

Dr. Biology:

Tell the difference you.

David:

They can tell the difference.

Dr. Biology:

Do they just ignore them?

David:

The ones that they're not used to, they might display a little bit, but it's not very much. And then if you show them the one that they're used to or the one that's that they're found with on that island, they display a lot to that. Now, interestingly, though, other islands where there have been no other species that they've evolved with, they do not discriminate. They actually are quite happy to display to anything that they see. You plop it down in front of them and then they start displaying to it. 

And so that raises a question about why that might be the case. And we are speculating now, but it is very possible that at one time some of these islands may have been connected together such that multiple species had the opportunity to interact with one another, and the ability to discriminate one species from another would be important in terms of mate recognition and so forth. And so that may have just stuck with that particular species. 

In other cases, the islands have not been connected to any other islands. And so those lizards that evolved there would have never had the opportunity to interact with any other species. And so, you find that species recognition is relaxed in those.

Dr. Biology:

And how many robots have you had to build to do this?

David:

I've built probably ten or more of these different robots over the years. Yeah.

Dr. Biology:

Wow. Now at the beginning of the show, I said, you work on lizards, but you also have worked on another animal. Let's talk about your spiders that you've worked with.

David:

All right. I work with jumping spiders and jumping spiders there. I think the reason that I was attracted to jumping spiders is because they act a lot like little vertebrates. They stalk their prey like cats do. They interact visually with their prey and with other members of their species. And in fact, you find that they can be quite colorful like birds are and that their displays can also be very active kinds of displays and very elaborate sorts of displays that they have. When I mean their displays, I mean their behavior pattern. 

And many of these jumping spiders incorporate all sorts of body movements into their display as well as having eight legs. They may use all eight of their legs in their displays when they do their things. And then in addition to that, they may actually include some vibratory information and so they may vibrate against the substrate and so it really becomes quite a multi-modal kind of display that they have where they are using many different aspects, visual displays, posturing, sound displays. They may be using even chemicals in the silk that they lay down, that sort of thing.

Dr. Biology:

Yeah, they're extremely colorful. We will certainly put in the chapter notes a picture of a jumping spider. I would say the glamor child of the spider world because they are so amazingly pretty. They're also most of them are incredibly tiny.

David:

They're very small.

Dr. Biology:

We also talk about basically the jumping spider dance.

David:

Right.

Dr. Biology:

I mean, they actually dance.

David:

Yeah, I would call it a dance. Yes.

Dr. Biology:

Yeah, yeah. And so, we have color. We have dance. We have potentially chemicals. For example, ants are a really good example of where their communication is chemical. So, David, when we talk about these jumping spiders, there are so many of them. I don't even know what the number would be. Can you tell us a little bit more about the one that you're working with?

David:

Certainly, this is a really unique species of jumping spider in that the males are what we call dimorphic, dimorphic meaning that they have different looks about them or that there are two different types of males really within this species. And that's where the word dimorphism comes from. And what we have is a male, that is what we call the tufted male. 

This male has an all-black body. It has white-colored legs. And on top of its head, it actually has three tufts of hair. Essentially, it's an arthropod hair, but they have hair on top of their head. The other morph in this species or the other type of male in this species is what we call the gray male. The gray male looks completely different. It is zebra-striped. So, it's a black and white striped male. It does not have the tufts at all. And it has a white sort of stripe across the top of its eyes. Its legs are all striped, and it has these bright orange colored, what we call pedipalps. Pedipalps are these very small little legs that they have up around their mouth area, and they're brightly orange colored. 

Now, in addition to the fact that they are very different in their looks or their morphology, they also behave different when they court the female. The tufted male will spot a female from a considerable distance, many body lengths away, and he'll stop and place and then raise his body up and stilt and then his legs come up above his head and then he waves them vigorously at the female. And his abdomen is going back and forth. But he's just standing there at this distance and does that. 

The gray male approaches the female to within just a few centimeters, just a very short distance away from the female. And then he drops down into this little position where he has his legs pointed forward in kind of a triangle or an arrow-like shape. And then he doesn't just stand there. He actually sidles back and forth. And so, he goes back and forth in front of the female in this sort of half-moon pattern. So, these males are very different in how they look and how they behave. When they are courting a female.

Dr. Biology:

Is there any preference? I mean, it can't be much of one or both of the males wouldn't continue to exist.

David:

There does not seem to be a preference for one male versus the other. Females seem to base their choice on which male is capable of attracting her attention first if given the opportunity to mate with both at the same time. How often that actually happens in the field or in the wild? We're not certain but if one male starts to court her, that's generally the male that she's going to pick, whether it be tufted, whether it be gray. And so, it's based largely on which male gets her attention first.

Dr. Biology:

When you've been doing your research, there are times when scientists discover something or something quite by accident or have a surprise. With your spiders, have you seen anything unusual that you just didn't really expect?

David:

Well, the discovery that jumping spiders respond to video images was really done really quite by accident. We're trying to figure out maybe if there was a way to determine which of these two different body forms the females might have a preference for. And when thinking about those sorts of things, you'd like to have a way in which you can control the behavior and the morphology. We just didn't have that. 

And one day I was in the lab at Cincinnati, and I was feeding the spiders. But at the same time, I was watching a little projected sequence of a male courtship on the wall in the lab that I was working in. And I noticed that the females that were in their cages had all come down to the end of their cage. And was also watching the male on the wall in his courtship display. And so, I thought, Wow, this is really pretty interesting. And I grabbed a piece of tracing paper and I taped it to the end of the female's little cage and then moved the projector in close so that it was life-size for her and then replayed it. And all of a sudden, the female saw that and ran down to the end and she started displaying her little receptivity display towards that projected image. 

It turns out that projected images are similar to video images. And so, we tested whether or not females would respond to these video images, because once they're video, you can then manipulate the video using computers. And so that led to computer animation of these males and being able then to really control their behavior and their morphology and it led to a whole suite of studies where we actually changed the tufted male into a gray male and the gray male into a tufted male.

Dr. Biology:

So, you've become a jumping spider movie producer.

David:

Absolutely, yes.

Dr. Biology:

[laughter] I love it. Wow. You supply popcorn for them.

Dr. Biology:

Yeah. [laughter] In the form of crickets.

Dr. Biology:

In the form of crickets. Okay. All right. David:, before anyone gets to leave, Ask A Biologist. There are always three questions I ask. So, are you ready?

David:

I'm ready.

Dr. Biology:

The first question is, do you recall if you had a moment in your life where you really knew this is it? I am going to be a scientist. That's my path.

David:

I did. I was really quite young at the time. And it happened when, unfortunately, my grandfather had passed away. We had been visiting what I call our farm and my grandfather, and this was around Easter time. And he said, next time we come up, we're going to go out and get to see the snakes. We're going to go out and collect the snakes.

And he passed away before we could return to the farm. And I remember very distinctly afterwards walking with my mother out around the area there and saying, you know, he never did get to show me those snakes. And so, I think from that point on, I was always interested in biology and nature. And I was, you know, very enthusiastic about frog collecting and snake collecting and doing all kinds of things as a child.

And then I was very fortunate to have some very good mentors. Once I got into my undergraduate and throughout my graduate career, Jim Gillingham was a herpetologist at Central Michigan University and really inspired me to work on research at a very young age and get involved. And he and I did some studies on anoles, and we did some studies on turtle behavior and snake combat behavior, and a variety of different things.

And then he actually encourage me to diversify and going forward for my Ph.D. work and to diversify into some of the invertebrates. And that's what connected me up with George Utes at University of Cincinnati. And George and I have become very good friends and colleague to this day. We worked together on a number of the projects that were associated with my Ph.D. work, and then afterwards continued work on wolf spiders and wolf spider mating behavior and male male interactions in wolf spiders eavesdropping and a number of other things like that.

Dr. Biology:

Okay. Now, that is the easy question. The harder question is I'm going to take it all away from you. You don't get to be a scientist. All my scientists, or least all the ones I've been on the show love teaching, so I take away your teaching. So, what I want you to do is just if you could do anything or be anything other than being a scientist, which I've taken away from you, what would you be or do?

David:

I might be a mechanic because I really like tinkering. I like tinkering around with things, and I like to figure out how things operate like that. And so, I might end up being a mechanic.

Dr. Biology:

Right, And do you work on cars at all?

David:

I do. I try to as best as I can. Yeah. I'm really interested in particularly older cars and things like that. And I've done a little bit of car restoration over the years, and I think that would be a lot of fun to do.

Dr. Biology:

I agree. I actually have a 1974 screaming yellow super Beetle Volkswagen.

David:

Wow.

Dr. Biology:

First car I ever owned, and I still own it.

David:

Wow. That's wonderful. 

Dr. Biology:

Yeah, it's the most popular car. And whenever I drive you know, I can have any of the other cars I have. No one pays any attention. But I would take that Volkswagen out and people smile whether they knew someone who had one, had one, the family had one, they saw it in the movie, that sort of thing. All right. The last question, David, this one is for those future scientists. What advice would you have for a future biologist?

David:

Explore your interest. You know, things that might not seem particularly relevant at that particular time, I think can actually play into helping you learn more and helping you develop your goals and where you want to be. So, I would say think very broadly about things in the case of connecting up with a music professor. Think out of the box because a lot of times those are the sorts of things that are going to bring a lot of your ideas together and help move you forward.

Dr. Biology:

Great advice. I think it's one of several things that we've heard on this show that have been really, really valuable for our future scientists. Well, David, I want to thank you for visiting with me on Ask A Biologist

David:

Thank you. I really appreciate the opportunity to do this. This was really wonderful.

Dr. Biology:

You have been listening to Ask A Biologist. My guest has been biologist David Clark, a professor from Alma College who has been using lizard robots and spider movies to unlock the story of animal communication and their visual displays. 

If you want to learn more about this work, the lizards or the jumping spiders, or maybe both. We will include images and links in the story notes, and transcript. And if you have a podcast app player that displays our chapter links and images, you will be able to see them as you listen to the episode. 

The Ask A Biologist podcast is usually produced on the campus of Arizona State University and is recorded in the Grassroots Studio housed in the School of Life Sciences, which is an academic unit of The College of Liberal Arts and Sciences. But for this show, we are at the annual Research Conference for the Society of Integrative and Comparative Biology, also known as SICB. And remember, even though our program is not broadcast live, you can still send us your questions about biology using our companion website. The address is askabiologist.asu.edu, or you can just Google the words. Ask A Biologist. 

As always. I'm Dr. Biology and I hope you're staying safe and healthy.