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Interview with Julie Miller

Journalist: Luke Peterson

Luke: Welcome to SciSection! My name is Luke Peterson and I am a journalist for the SciSection Radio Show broadcasted on the CFMU 93.3 FM radio station, and we are here today with Doctor Julie Miller. Thanks for taking the time to meet with me Dr. Miller.

Miller: Thank you for having me.

Luke: Can you begin by telling us about yourself, such as what your duties are at UCLA?

Miller: Sure, so I am a postdoc in the department of Ecology and Evolutionary biology, and I

study the behavior of ant colonies and I’ve got a few projects going at the moment but I

originally joined the lab interested in how the size of a ant-colony - so how many individuals in

the group - affects the ability of the group to coordinate and organize. You can imagine if you’re

in a very small group, like a class-project group with four people - that’s a very different sort of

activity than if you’re in a group of ten thousand individuals trying to write a report. So I wanted

to understand what kind of challenges large and small groups face when trying to do some

basic organizing and I approached that by thinking about what kind of organizational task that all colonies have to do. So I looked at feeding: how do ant colonies bring in food and how do they do that in a way that satisfies the needs of a colony. Like any animal they have to bring in

sugars and proteins and salts and fats and they have to do so that meets the minute-by-minute

needs of the colony. So there’s a group of ants that have to go out and get the food so most

ants; common knowledge among social-insect people, but not everyone’s a social impact

person, is that the queen doesn’t do most of anything. The real work is done by her daughters,

the workers. So I wanted to focus on this group of workers that goes out into the world and

brings back food. They are the key individuals that make sure that the colony is well-fed, and I

wanted to understand how foragers in large colonies and small colonies meet this challenge.

Luke: So do you think that there’s more specialization in a colony as its size increases? Also, do

you think that every ant has a specified role, or are there ants that don’t perform tasks as well as other ants? Is there a disparity in their performances?

Miller: So the first question about whether specialization increases with colony size, there is a lot of literature that suggests that this is the case, but it doesn’t seem to universally be true.

Generally we assume that that is happening. If we look between species, and sometimes if you

look between a colony that is true. So I would say yes with a big asterisk. Then the second

question was about if some individuals better at tasks than others?

Luke: Yeah, if ants that are supposed to do similar tasks go out into the world, would you expect that some ants can produce greater yields, like if there were ants that are scavengers? What do you think about that?

Miller: That’s not something I have specifically investigated, but there are people in my lab and

also in the greater community of researchers have found that that is the case. Certain

individuals are better at finding food or bringing back better yields, and that sometimes increases with experience; even though you’ve got a giant group of individuals, they have the

capacity to learn and get better at tasks. There’s not only a - some individuals are indeed

predisposed to doing some tasks better because genetically or developmentally they are better at doing those tasks, but sometimes they just get better with time. As you practice doing a skill more and more, you get better and better at it. So that is not something that I am specifically looking at with my research, but in a way I am looking at something more broader called the foragers, or the ants that go out and get food. It would be interesting to ask if the ones that go out, how variable are they in how much food they bring back, or how well they are at extracting resources.

Luke: It’s open ended. So what is like to do field work for someone in you reposition? What do

out look for? What sort of data do you look for?

Miller: They type of data depends on the questions. I love field work; I really just love observing

the animals in their environments and jut understanding what their day-to-day is like. When I go out to do fieldwork, most recently it has been to collect ants to bring them back into the lab

where I study their behavior often using video recording. It really varies depending on where you are, what species you’re working on, but more recently, my work on Argentine ants which are very locally abundant in Southern California - but they’re invasive - so this isn’t their native

habitat, but I go out to the parking lot behind my house and I pour water into a crack in the

sidewalk and ants come flooding out. So I’m sitting there on the concrete with an aspirator

which is like a special tool that entomologists often use to suck up the insects. So imagine a vile with a long tube attached to it and on one end of the tube you are sucking in air and there’s a little sucking tube that comes out of the vile where you point to the ants and then you suck up

the ants into the file but you’re not - there’s a filter - so you don't actually inhale them but you do inhale them sometimes in a failed filter situation. Basically you jt suck up the ants into these vials so you can transport them to the lab, But I’ve done fieldwork in South Africa, Costa Rica, and Trinidad, all these very different kinds of habitats. My work involves walking around, looking for ants that are out foraging, so I just look for ants walking around, sometimes in groups. Sometimes I set out baits and wait for ants to arrive and then I follow them back to their nest, so they’re bringing food back. If I’m looking for nests, that’s a good strategy; or if I'm looking to collect a few workers, or just to understand their foraging behavior; it’s fine to just walk around until you find the ants you’re looking for.

Luke: When you find colonies or nests of larger colonies, what’s so distinct about them? Can

you tell that there’s more specialization occurring there, is it more well-built? What makes it

distinct from other smaller nests?

Miller: That’s a great question that we don’t have a lot of answers to yet. When it comes to some basic things like; a larger colony is obviously going to have a larger nest - they’re going to

occupy more space. We tend to find that the workers in large colonies, or in species of large

colonies, tend to be smaller; the workers are tinier. This is a phenomenon of worker-

miniaturization in larger colony species, whereas in smaller species, the workers tend to be

larger. There’s sort of this syndrome that happens as you become a larger colony. The queens

tend to be much larger than the workers. The difference in morphology between the workers

and the queens becomes more extreme in larger colonies. As you have a larger queen, she can

then make more workers and be more efficient at her job at pumping out eggs, but that’s not

always true. Sometimes you get much more queens in larger colony species; this invasive

Argentine ant has lots of queens. I don’t remember the ratio of workers to queens, but a single

colony can have hundreds of queens, and we actually in California have this super-colony which

are these - the Argentine ants in their native range are actually aggressive towards one another. If one colony encounters another then they'll fight. Here in Southern California all the way up to the Bay Area and maybe even beyond that, when two neighboring colonies encounter each other, they will exchange workers and brood and food, and they’ll act as if they were a part of the same colony. That results in this super colony that is the size of California, basically, that is a colony of workers that are all tolerant of each other. That is an extreme case of this large colony size that has arrived at this highly tolerant behavior that is unique to the invasive range. In Argentina they don’t do this, but that’s an area that I’m not actively studying but that I think is totally fascinating. One thing I’m studying about large colony size that I haven’t mentioned that I’m working on yet is the nest itself. Several people in our lab want to know how nest architecture is affected by ant colony behavior and vice versa so how does architecture affect the behavior of the ants as well. I was entering the lab thinking about colony size and what kind of effects that would have on nest architecture and as a side project with the student Emma Won who graduated, we did this comparative analysis of nest architecture across species that varied in their colony size. I investigated all the literature where people had visual depictions of ant nests and what’s neat is that this ant biologist Walter Shekel pioneered this method of pouring molten metal into ant nests and then digging them out. You get these metal castings out of the nests and people have done this for various species and then published these images through publications studying various ants. We went through all these images that have been published and wanted to understand how the structure of these nests might vary in large vs small colonies. The first thing I really was curious to know was that if you are in a large colony like a human in a very large city, do you have to create connectivity between different parts of the nest more so in a large colony. It’s like having the city of LA without a freeway system; you need a way to connect the disparate parts. We also wanted to understand another way that these nests might be structured differently and that was by looking at how the nest is subdivided. Ant nests tend to have these things called chambers which are like bubbles where ants gather around and do various tasks like taking care of the brood, storing food, cleaning each other, throwing away waste. We wanted to analyze how the number/sizes of chambers might vary in large vs small colony-sized species. The idea - the hypothesis put forth by a biologist back in the 50s, he proposed that larger ant colonies probably have to subdivide their group into smaller working groups bc if those groups are so large, it is very hard to communicate with one another, kind of like how i talked about how you’re in a group project and talking with 10,000 individuals would be a mess, whereas if you are in a group of 4 or 5, then communication is more efficient. The idea is to subdivide your colony into more manageable sizes. I wanted to see if the nest would facilitate breaking down the group into those group sizes. The paper is still under revision but hopefully it will be published very soon. We found that there is these larger nests are more subdivided; they do increase in the number of these chambers without actually increasing the size of the chambers. The subgroup idea is at least supported; but we do not find that these nests are more highly connected which is surprising because how do they stay within contact with each other. It’s also potentially possible that it’s very energetically expensive to build a highly-connected nest that you got to dig all these extra tunnels to keep everybody connected; it may also impair the structural integrity of the nest. If you’re in the soil and you build too many tunnels, your walls may come crashing down. That’s a side project that I’ve been working on related to the nest architecture.

Luke: It seems like ants are very industrious. You mentioned that the queen doesn't have a lot

of oversight over things. I also read on your website - and I was fascinated by this - that there is

a species of ants called O. Berthudi and you referred to them as queenless ants, and I'm not

sure if you used the term “anarchy” to describe them, a “stable social anarchy,” maybe that was

a term you used. Can you elaborate a little about that?

Miller: I fell in love with these ants when I was a grad student and because they just seemed like

such a weird echo of our human societies in a weirdly more functional way. These ants have

evolutionarily lost the queen cast, so all of the ants are technically workers but weirdly they’ve

retained the ability to store sperm. This is a trait that most people will think about with the

workers is that the workers don’t mate. They can’t reproduce directly. Sometimes they can lay

male eggs which is another story, but the workers in this species retain the ability to mate and to store sperm. And that’s what gives them the ability to reproduce like a queen. There’s this

phenomenon of losing the queen cast which has evolved several times in ants, and there are a

couple of reasons why we think this has happened. We think this has to do with the risk of flying off and starting your own colony as a queen. There might be a lower risk strategy of letting everybody have a chance at it. The problem with that is the potential for competition between the workers: who gets to produce more offspring? Who gets to pass on more of their genetic material? That’s sort of this classic cooperation conundrum which exists across all animals that cooperate. And this species, in most queenless ant species, they resolve this conflict by forming these dominance hierarchies where maybe only one or two individuals gets to monopolize reproduction, and they end up being functionally like a queen, and all the workers tend to functionally be like workers. But in this species that was not the case: they break that rule, they don’t have the “monarchy” that we’re used to in ant colonies. These ants instead have a sort of oligarchy where sometimes up to half of the colony continues to just peacefully coexist as queenlike workers. We call those gammorgates by the way. I want to point out just to mention this, this system and species was originally pioneered and described and studied by the late ant biologist Christian Peters who just passed away a couple weeks ago and was a really inspirational biologist for people in the ant world and I just wanted to acknowledge that his work was what led to my fascination with this system. But anyway, he found this phenomenon, so I wanted to understand what is the difference here in these ants versus all of the other ones that have this monarchy instead. Some of the pioneering work he did showed that it had to do with the fact that over the course of a year, a single colony with many queens will actually bud off, kind of like amoeba budding off, and forming these multiple sub colonies. At the end of a year, most colonies just have one to three queens, and over time they become more monarchy-like and then at that time of the year when they’re more - when each sub colony has few reproductives - the males are released. The males in ant colonies are like sperm rockets because they just are little flying sperm vesicles. They just fly around, mate, and die. So once the males are released and mate with the next generation of worker-like queens, you really ultimately from a genetic standpoint, you have a monarchy in the ant colony like the other ants. The cooperation that we see is - they’re not really foregoing or compromising their reproduction because in the end they get their own share. There’s that but that’s sort of the background. What I wanted to understand was that we think this is happening, but is there actually any evidence that there is some kind of cryptic dominance hierarchy happening, even though we don’t see it behaviorally. Theoretically, some of these ants might get ahead and get more of their genetic material passed on if they were in some way able to monopolize reproduction either chemically by suppressing other individuals by producing more of a chemical that suppresses others’ reproduction. I did this experiment where I artificially created cheaters, being individuals who had more resources and produced more eggs and were just more reproductive. I wanted to see if the colony would reject them or just continue to tolerate this cheater-ant, and it turns out that they just tolerated her excess reproduction, so whether that actually happens in the real system is yet to be determined, but it shows that these anarchist colonies, or at least that an important feature of them is, that they are very tolerant of one another and that they permit cheating and that’s not to say that cheating occurs, but that they are at least tolerant of it.

Luke: How often do typical individuals in these colonies reproduce?

Miller: The thing is that when ants are reproducing - it means by what you mean by reproducing. Workers like I said are female, so they’re constantly laying worker-eggs, but only once a year in this system do they actually lay eggs that become reproductive, so become future queen-like workers and male eggs. So the males actually are produced without sperm do males - bees, wasps, ants all produce males without mating. It’s only one set of chromosomes, which we call haploid, so a worker can easily produce and lay an egg without mating and produce males. They’re asexual as we say, they’ll go on to pass on their genetic material. Producing queens or workers, you need two to mate. In this system it’s a little weird because they’re producing workers that might go on to reproduce. It happens once a year when the season is right.

Luke: For the species that we’ve been talking about, they function normally? They’ve been able

to carry on well?

Miller: Yeah they’ve been very successful. In the area that I’ve been studying them, they’ve

been the dominant species in this scrub habitat. They’re not hurting; they’re doing well.

Luke: I think this might be a nice place to end it. Is there anything else that you want to say or


Miller: I guess one thing I always like - the main question I get from people is how to get rid of

the ants in my kitchen, and I hope that by listening to some of the narratives and the stories that ants can provide, it helps increases people’s appreciation of the ants around them. I’m all for killing the invasive species that are attacking your kitchen, but I’d say stop for a second and take a look at what they’re doing and appreciate how well they’re functioning as a society and maybe we can learn something, especially now about how groups work together.

Luke: Ok, so thanks Dr. Miller for meeting with me today. That’s it for this week of

SciSection! Make sure to check out our podcast available on global platforms for our latest interviews, and I’ll talk to you later!


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