In a paper published in Animal Behaviour in 1984, Michael Taborsky presented a cost-benefit analysis of helping behaviour in the cichlid fish Lamprologus brichardi. In this species, individuals of earlier broods stay on in their parents’ territories and contribute to the care of the current brood. Evidence from field observations and lab experiments, suggested that helping pays off for L. brichardi when the cost of reduced growth rate due to investment in helping and low rank of helpers in the family hierarchy is compensated by: 1. reduced risk of mortality provided by the family and 2. kin-related benefits obtained through increasing their parents’ breeding success. Thirty-nine years after the paper was published, I spoke to Michael Taborsky about his motivation to carry out this study, memories of field and lab work, and his reflections on the study’s findings and interpretations:
Citation: Taborsky, M. (1984). Broodcare helpers in the cichlid fish Lamprologus brichardi: their costs and benefits. Animal Behaviour, 32(4), 1236-1252.
Date of interview: 22nd February 2023; conducted in-person at the Wissenschaftskolleg zu Berlin.
Interview transcript edited by Joyshree Chanam
Hari Sridhar: Michael, I want to start by asking you to, maybe, provide a little background and context to this work. I noticed that you’ve been working on cichlids, right from the beginning of your career. This was a paper that came soon after your PhD, and you cite your PhD in this paper. So, can you talk a little bit about how you got interested in cichlids, and also how you got interested in the question of cooperative breeding in cichlids?
Michael Taborsky: Yes. First, I would like to thank you for this opportunity to speak about this paper because it reports on one of my most important studies, and it is more or less summarizing a large part of my PhD thesis. It is not the only paper that came out of that thesis, but it was the essence of combining some important results of the PhD thesis. Well, to get to your question how I got interested in cichlids, and cooperative breeding in particular, like so many reasons for scientific research it was more or less a chance event. I was a student at the University of Vienna, and I started to study zoology and biology in general, because I was interested in behaviour. I wanted to understand how and why animals behave. And in Vienna, it was difficult to find someone who was really doing in-depth studies of behaviour. So, I was particularly interested in the Max-Planck-Institute of Behavioural Physiology, as it was called at the time, in Seewiesen, Bavaria, south of Munich. This was a place that everyone knew, at least in Austria, because Konrad Lorenz had been working there and established that institute. Konrad Lorenz was a Nobel Prize winner a few years before and he was an important figure in science in Austria and in Germany at the time. Nevertheless, when I got to Seewiesen to do my PhD there, together with my girlfriend Dominique Limberger (now Dominique Hall), Lorenz had left already. He had retired and his successor was Wolfgang Wickler. We wanted just to get an opportunity to do a PhD-thesis there, both of us. Wickler said, well, we first need to know you a little bit, your qualities and abilities and things like that. I should add that this was after studying only four semesters at the University of Vienna, so it was at a very early stage of our studies. And at that time, there was no doctoral program, no master’s program, no bachelor’s program whatsoever. In Vienna, you could only finish your studies in biology with a PhD, this was the only way to finish it. But of course, usually you don’t start a PhD after being at university for two years only. So, we were greenhorns as it were. Fortunately, Wickler was generous enough to let us help in raising geese, because one of the researchers in his department was doing experimental studies with bar-headed geese, and we were allowed to help out there. We raised geese and we did experiments with them under the supervision of this researcher, Jürg Lamprecht. And apparently, we performed well enough so that at the end of this period in the summer, I think it was ’76, Wickler offered both of us a PhD position, but we had to share one stipend. So, we got one position for two people, which was okay, we were partners and could survive on very little money. This was originally for two years only. Wickler said, if we’re interested in cooperative breeding, or in mating systems of fish, especially cichlids, then he would have a very interesting observation that a masters’ student had made a year before at his institute, which showed that in a particular species of cichlids from Lake Tanganyika, the young do not disperse after they became adult, but they rather stay in the parental territory and help raising offspring of later broods. This was only known from birds and mammals at that time. So, Wickler realized that this was an extremely interesting system. If fish really showed that kind of social organisation, then you could experimentally do a lot more than with birds and mammals. Hence, we happily chose this theme for our PhD, and we shared the resources. I was focusing on the alloparental care and cooperative breeding system, and my partner, Dominique, was studying the mating system, because, interestingly, these fish were also haremic; they were either breeding in monogamous pairs or in harems. Dominique was interested in the ecology of that diversity of the breeding system. This was the start of our study. And then we did a lot of experimental work in the lab and also some fieldwork in Burundi, at that time at the northern edge of Lake Tanganyika. Finally, we ended up with two PhD theses. And this particular paper, as I said, summarizes part of my own work on these fish, and combines field work and lab work, with a strong emphasis on lab work because we did much more work in the laboratory than in the field due to the possibility to do experiments there under controlled conditions. In total our study took five years, not only two. We got a prolongation for two more years, and at the end I think we still got some money to complete our study. Regarding this particular paper, what I tried to do was to give an overview of my personal understanding of how you can explain the evolution of such a complex system in fish. This was possible by performing a stringent cost-benefit analysis of helpers and breeders of the involved parties, and varying experimental conditions by which we tried to manipulate the system in ways that we could really measure fitness correlates of behavioural responses to our manipulations. Not necessarily lifetime fitness, which of course would not be fully possible in the laboratory anyway, under non-natural conditions; but fitness correlates. And this paper combines these different experiments that I’ve done for investigating that particular question.
HS: Just a matter of detail, what was the name of the Master’s student who did the study that motivated this work? And did you have the opportunity to meet this person?
MT: This was Klaus Kalas. We never met him. He had left before we came to Seewiesen. He was Austrian also and had moved to Salzburg to work with his wife Sybille Kalas. He was not involved in basic research afterwards. This was his only study in that particular direction, behavioural research and basic science. (Klaus Kalas and Sybille’s works)
HS: And was this part of an already existing research program on cichlid fishes in Africa or was Klaus Kalas’s study a one off, just his interest?
MT: That’s a good question. There was a history of studies of African cichlids in Seewiesen at this institute, already initiated by Konrad Lorenz who was interested in this taxon. But he and his employees and students never did any systematic experimental studies. As a side comment, Lorenz was more of a philosopher than a natural scientist. He never performed controlled experiments or analysed experimental data, things like that. Anyway, there was a history of keeping cichlids and studying cichlids, albeit not necessarily from Lake Tanganyika. Actually, I think it was the first Lake Tanganyika cichlid that was studied there. I have no idea how Kalas got these fish and why he was studying them. I only know that they were popular or at least easily available in the aquarium trade at that time. On the northern end of Lake Tanganyika in Bujumbura, the capital of Burundi, there was a naturalist and commercial fish exporter named Brichard, Pierre Brichard. Our study species was called Lamprologus [later: Neolamprologus] brichardi at that time, named after him. He exported fish to Europe and the USA. So, these fish were commercially available.
A very funny incident happened when we met other people at a conference in Amsterdam. It was a meeting organised by PhD students for PhD students, just to have an exchange of people interested in fish behaviour. The organization that organised this meeting was founded by young fish biologists interested particularly in social behaviour, reproductive behaviour, and related subjects. The venue had aquaria at the edges of the meeting room, and one of these aquaria kept our species, Lamprologus brichardi. And just by chance, I was standing near to this aquarium when another student (Sven Jakobsson from Stockholm) was saying to someone else that he was interested in that particular species and that he was just starting a PhD study on it, because he observed that they have helpers or individuals that do not disperse right after being mature. I was, of course, extremely stunned and immediately spoke with him and told him that Dominique and I were studying that particular species exactly in this particular direction, and that we should somehow coordinate to avoid repeating things. We kept communicating about it also after the meeting and Sven finally decided to study something else, because he thought we had already proceeded too far, so it would be difficult for him to find a niche and do something that would not overlap too much with what we were doing. But anyway, this was a chance event. If we had not met, he would have probably done a similar study, and come up with similar publications in a similar time frame, which of course is bound to cause problems if you don’t know each other. This was before email and the internet existed. Communication was only by meeting people or by snail mail. So, we would not have known about each other before the publication of our respective studies. I know of other cases where people developed similar projects in parallel without knowing from each other, which sometimes caused a lot of troubles in the end.
HS: Quite a fortunate coincidence to be there when this happened! Do you remember which year this meeting was?
MT: I think it was probably spring ’77 or so.
HS: After you had gone and started the work in Africa and come back?
MT: No no. Our fieldwork happened in summer ’78. So, it was before we went to the field. It was after we had started our study in the lab.
HS: And do you remember who the biologists were who organized this meeting you said, for biologists?
MT: Yes. The major organiser was Mark H.J. Nelissen, a Belgian fish biologist who was working with cichlids for a long time. And he was also a founder of the IAFE, the International Association of Fish Ethologists, which was hosting this meeting. We kept contact for some time. And there were one or two other meetings where we also went, but after some time this organization ceased to exist. They had a newsletter where they published short reports about the work of the participants of these meetings.
HS: And at this point, when Wickler asked you if you wanted to work on this topic, did you have any experience on fishes? Had you kept fishes? Had you watched fishes any time before that?
MT: I had watched fishes before that, but never had any fish in an aquarium or so. My first scientific work was while I was a student during a practical in Yugoslavia, where Dominique and I observed a blenny species defending feeding territories. And feeding territories, I should say just quickly as a side note, are extremely rare in fishes because usually the food that they consume is not replenished quickly enough so that it’s economic to defend a territory. But this particular species, Parablennius sanguinolentus, feeds exclusively on green algae, which are very prolific. And when you defend a lawn of algae, or turf, then you can obtain enough energy to subsist on your little territory, your lawn. We studied particularly the circadian rhythm that they showed because this seemed quite an interesting aspect. These algae don’t have storage organs. They accumulate carbohydrates and proteins during daytime, and at night they divide. So, in the morning they have much less nutritional value than in the afternoon. And we observed that the blennies were feeding on their lawns mainly in the afternoon. There was a very significant increase of feeding activity during daytime before it dropped when it got dark. This was what we, Dominique Limberger and I, studied and it resulted in our first publication, in 1980. So, yes, we had a little experience with observing fish, but we had no experience with keeping fish or performing experiments with them. I also had no experience with, or knowledge about, cooperative breeding, complex social systems, or anything like that.
HS: But yet when Wickler asked you, you had no doubt in saying yes to this project.
MT: Yes of course! It immediately seemed highly fascinating, absolutely interesting! Then we started reading about such kinds of systems and about cichlids and all the sources that were available at that time. And it really intrigued us right from the start. The particular thing that appeared to us so fantastic was that you seem to have a relatively complex social system in a species where you can manipulate the environment, because you can keep them in an aquarium where you can modify their ecology. And you can even manipulate groups, group compositions, behaviour, all these sorts of things that people who were studying cooperative breeding systems in birds and mammals could never do; or at least not in a way so that you can obtain data that can be related somehow to fitness effects. So, it was a unique opportunity to answer some really interesting questions regarding the evolution of such kinds of systems.
HS: Did Wickler become your PhD Advisor?
MT: Yes, he was our supervisor.
HS: And was there any kind of doubts about going and working in Africa? Was this the first time for you to go to Africa?
MT: We were extremely keen to go there, and we were strongly pressing in that direction. There was some resistance from Wickler and from others in his department. They were pretty sceptical whether we could really cope, and also because of the costs of the expedition. But we really pushed hard and convinced Wickler that it’s necessary to understand the system under field conditions. Otherwise, how can you draw any conclusions without ever having seen this in the field? Wickler agreed and supported us in the end. And we were lucky to get support in the field from Pierre Brichard, the naturalist who ran this fish export company in Bujumbura. He helped us finding our study species. It was an extremely adventurous trip. We had so many exciting, both wonderful but also disturbing events happening, it was amazing! When we arrived, there was a cholera epidemic, so nobody was allowed to go to the lake, not even approach the lake shore. It was completely forbidden, because they feared that the lake was contaminated by wastewater. The fishermen were not allowed to fish. They really had problems in getting their subsistence because fishing provided their only income. We had to get a special permit to be allowed to dive, which involved quite a procedure. Dominique, my girlfriend, had a French mother, so she was perfect in speaking French. She obtained this permit after two weeks or so of negotiating with the authorities and taking mandatory prophylaxis medicine in Bujumbura. And then we had to find a place to live. We found a fish processing factory 40 kilometres south of Bujumbura, where we were able to rent a little hut in the fish drying facility. And then we had to find someone to boat us to the place where we could find our fish, with all the diving equipment. In this regard it was lucky for us that the fishermen could not fish, because this enabled us to find a fisherman with a boat that we could rent, and he was very happy to be paid for that as he was not allowed to fish anyway. He brought us to the place where we finally found our fish and could do our study. We were lucky to find a place where the fish occurred in very shallow water, at four-five meters depth, because we only had one diving tank of 10 litres each. We had a compressor with us but we could not transport it to the field site as it was too heavy; it was kept where we lived. So, we could only have one tank filling per day, which allowed us to dive for about four hours. This was okay because of the shallow water depth.
HS: Did you have to train to dive?
MT: Yes, we had to. We had to get a diving license and to train how to dive. We had never done that before. We did our dive training in Munich, 30 kilometres away from the Max-Planck-Institute in Seeweisen, in the Olympic swimming competition pool. It had a 50-meter swimming lane and was deep enough to do dive trainings there. That’s where we got our diving licences, and made our first experience with diving.
HS: How long did you stay in Africa?
MT: It was a very short stay, roughly two months. It took a long time until we could even start to work, so we had only six and a half weeks to collect data and worked like hell. We were extremely busy and fortunately successful in data collection. We also had some very interesting interactions with hippos, which are really, really dangerous! They are certainly the most dangerous animals at Lake Tanganyika. Pierre Brichard and his team had told us when we first arrived there, that they had just lost the fourth diver to a hippo a week before we arrived. And they warned us so much. He said whenever you encounter a hippo underwater you should know what to do because otherwise, you’re dead. And so, we were extremely wary in the beginning. When we dived, if we heard something or so, we were always looking behind. The problem is that hippos travel underwater. They feed on land and spend much time in water lying at the surface. But when they travel from one area to another, they do so by diving at a depth of three to four meters or so, and they walk on the ground underwater. This was exactly the depth that we were diving. And there were hippos all over the place. In the beginning we were really afraid of these animals, even more so because of one unfortunate incident when we were still searching for our fish. Near the place where we stayed, we were told there were no hippos usually, and it’s safe for us to look. There we didn’t find our fish. So, we went to the other side where they said we should not go. But anyway, what could we do? We needed to find our fish. So, we went there snorkelling with a weight belt and diving suit. And there was a bay with reeds where the hippos were feeding. We saw them. And I said to my girlfriend that I will swim across the bay to the other tip where there was no reed – I thought there should not be any hippos – just to check whether our fish could be found there. And when I approached that tip of the bay, just 10 meters in front of me a hippo emerged and looked back at me and defecated, which means splashing about the faeces and is a signal of territoriality … well, it was my record in swimming speed to head back to where I came from! Hippos are extremely fast, both on land and in the water. I didn’t look back. I just swam. I had flippers so I was pretty fast. And when I arrived at the other tip of the bay, where Dominique was waiting for me, I said, “Don’t worry, it did not follow me”. I was not sure about that, but I didn’t want her to panic. But she hadn’t realized anything. She panicked because of my exhaustion and because I was upset, and jumped into the water! We were swimming back towards the place where we lived, just to get onto safe ground. Suddenly, she panicked because she felt something heavy on her foot. We just kept on swimming. And later we found out that she had lost her weight belt. When she was waiting for me, she had opened the weight belt for comfort and because of the panic, she forgot to close it. So, it was her weight belt that fell on her ankle, and she thought she was attacked – poor Dominique! Anyway, we had some strange experiences, not really dangerous, but they appeared to be dangerous. And then, during the whole period that we collected data, we never saw hippos at the place where we did our observations. So, we felt really secure there – until the day before last.
We used up our air to the last drop every day because we only had these four hours that we could spend underwater with these 10 litres of compressed air for one day. Therefore, when we got to the surface, there was no air left in the tank. What you should do when you encounter a hippo in the water, underwater, is to go deep, because they can’t go very deep. So, when you go down five to 10 meters, you’re on the safe side. But if you don’t have any air, you cannot go deep, and you’re very clumsy with all this diving equipment and cannot swim fast or anything.
So, on the day before the last, after surfacing from my diving, I swam to the shore as usual, to get out. When I stood up, I turned around and there was a hippo head emerging exactly at the point where I had surfaced just a few seconds before, perhaps 10-15 seconds earlier. I was so lucky! And on the last day of diving, I was extremely afraid of hippos, of course, but nothing happened.
HS: Did you have people to assist you with the work from the area?
MT: No, not really. We were on our own. The fisherman who drove the boat was at the shore waiting for us, but he did not interfere in any way. We asked him that if he sees a hippo somewhere on the surface, he should warn us by banging against the boat, which we would hear. But that never happened. Another thing that was a bit strange was that sometimes we were stoned by people! So, when we emerged from our dive to swim on the surface to the shore, we got stones thrown at our heads because people, especially kids, thought we were hippos! We had black diving suits, gear and cap, everything black. Local people did not know divers, had not experienced anything like that. The response of people to hippos is actually one of the reasons why they are so dangerous. Whenever people see hippos, they throw stones at them to drive them away, because they’re afraid of them. But that makes hippos afraid of people and therefore they attack them in return. It’s a vicious circle.
HS: You mentioned a place called Magara in Burundi. Is that where you were based?
MT: That was the closest village to this fish drying plant where we lived. That’s where the market was where we bought our food.
HS: What are the memories you have of that time? What was life like? Your interactions with people?
MT: Life was very busy, because of the diving that we did. And apart from that, we had to prepare food ourselves on open fire and we had to get the things that were available, which was not plenty. It was a poor area. We had rats in our hut that were eating our flour at night, if we did not cover it well enough. And running over our beds, even when we’re in there! We had a lot of animals around. There was also a guinea pig in our hut! I don’t know how they got this guinea pig, and I don’t know why. They are South American animals. So, it had been bought or acquired somehow, by the people running this factory. This animal was living under a cupboard in our kitchen. It was also a depressing time, especially in the beginning, because of the cholera epidemic. That affected a lot of people and many died. And there was no health system out in the countryside. In Bujumbura there was, but that was 40 km away. So, when people got ill, their friends and relatives sometimes brought the diseased person to this fish processing plant, because it was a kind of ‘official institution’. It had nothing to do with health services, of course. But people thought this might be a place where they can get some help or medication. Occasionally in the middle of night, people who carried diseased people were banging on our door asking for help. And they carried patients right to Bujumbura for 40 kilometres sometimes. It was quite an extreme hardship for the population.
HS: Were there ways in which you could help?
MT: No, we had no means to help. We had no medication, no vehicle, nothing at all. So, there was no possibility.
HS: The species that you chose to study, was it the same species that the earlier study had also used?
MT: Yes.
HS: Was that the reason you decided to study the same species?
MT: Yes, yes.
HS: Was the study focused on only one species?
MT:Yes, it was focused on one. We were interested to know whether this was also found in other related species. So, we got some other species where we also observed this kind of cooperative breeding system in the field, and subsequently in the lab. Julidochromis species belong to a different genus, but they are relatively closely related. We did some experimental studies also with them, but we have never published the data because it was not sufficient for a substantial publication. But at least we knew that this kind of system is not unique in the particular species that we mainly studied.
HS: What did the travel to your field site from Europe involve, at that point? How did you go? Were there flights?
MT: Oh yes, the flights! This was also quite adventurous because we had to go through Cairo, and then Nairobi. And from Nairobi, there was a flight to Bujumbura. When we arrived in Nairobi, we had to change planes, so we had to take out the luggage we brought from Cairo to change to a different plane. And our luggage did not appear. But, fortunately, in Cairo we saw that our luggage was put on the plane. We knew that in Cairo there was a lot of chaos and a lot of luggage disappears. There were big halls at that time in Cairo airport, fully stuffed with luggage that were left there because the transport had not functioned or whatever. Anyway, so we saw that our luggage was brought to the plane. We knew it was on the plane, but it was not coming out. So, I crawled through the separations on the luggage conveyor belts, these plastic sheets that let luggage come in from the other side. I crawled through that and ran out to the airplane and said to the guard I know that our luggage is in there, they have to get it out. They were of course upset. The security measures at that time are not comparable to today, however. Today I would have been immediately arrested. They were upset, but they saw the problem and allowed me to get into the cargo compartment of the aircraft. The plane had already been reloaded for the flight back to Cairo. I had to go past some huge dogs – they had dogs in big containers and all these sorts of things – to find our luggage. And it was there! It was at the end of the luggage containing compartment of the airplane. Perhaps the staff had just been too lazy to unload it, because the luggage was heavy and big with all our diving gear, the compressor and everything. Now they had to unload some of the luggage they had loaded already for the return flight, not funny. In the end we got to Bujumbura with all our equipment. There were many adventures, as I said, on this trip.
HS: Did you do the lab work back in Europe, or did you set up a lab there?
MT: No, no. All the lab work was done at Seewiesen.
HS: Was there already a lab?
MT: Yes, there was a lab, and it was actually brand new. A large aquarium facility was built for Wickler’s department just when we assisted with the experiments on bar-headed geese, which nobody had used before. This was a really lucky coincidence because when we arrived in Seewiesen, Wickler had just about taken over from Lorenz’s department, which was completely rebuilt due to this leadership change – a typical effect of the regular Max-Planck policy. And Wickler was very much interested in fish behaviour, so he insisted to have enough aquarium rooms in the cellar of the new building. There were five or six really large aquarium rooms, equipped with aquaria, fully useful, but without any people working on fish. There were two other PhD students starting concurrently with us, pursuing different projects with different species. But that was all. Dominique and I had, at that time, 120 tanks among the two of us. We had to do all the service amongst ourselves, all the surveillance, cleaning and feeding everywhere, as we did not have any support from technical staff. This was a lot of work taking about four or four and a half hours every day, just the maintenance.
HS: And what did transporting the fish from Africa involve?
MT: We got exports through Brichard’s company. We imported them through the airport in Munich. We got them delivered in Munich and brought them to the institute.
HS: Once the field work was over, and you came back, how much longer did the lab work and the experiments take?
MT: Well, the field work was, I would say one third into the PhD thesis. It was not at the beginning, so we already knew what to do in the field. And that was quite important because as the field work was very limited in time, we needed to know really what we wanted to ask. We had a very, very strict program about which data we would like to collect in the field. And that was only possible because we knew already quite a bit from our lab study before. But in turn the data we obtained in the field provided important information for our upcoming lab experiments.
HS: The paper has some natural history information about the species. Was that already known or was that something that came from that from your field work?
MT: That came from our field work.
HS: And the protocols that you used for the experiments and the laboratory work, was that something that you developed yourself for the work?
MT:Yes. During our PhD, we did a lot of observations, hours and hours of behavioural observations. There’s a lot of behavioural details in this paper. And that involved long times sitting in front of the aquaria, quietly sitting of course, because we didn’t want to affect the fish in their behaviour. We had a special apparatus with which we could record data on paper strips. You only had to move the fingers on a custom-built keybord, which the fish did not see. You could sit right in front of the aquarium. But if you do that for hours every day, in the climate of say 26 to 28 degrees centigrade and quite high humidity because of the aquaria, you get very tired.
HS: You mean in the lab in Europe?
MT: In Seewiesen, yes.
HS: But the temperature is maintained at that?
MT: Yeah, because that’s the temperature of the water these fish need. And the rooms have about the same temperatures as the aquaria.
HS: Say a little more about how the paper tape works.
MT: Well, it’s a strip of paper that gets punched with holes when you press a key, and it’s constantly moving forward. Quite similar to a typewriter, but instead of the paper sheet that is moving in front of the letters for getting impressed by your keys, it’s just the punch that makes holes. And then this paper tape can be read by a computer. This was quite a fancy technique at the time. It was specially developed for us for this particular purpose. I think nobody else had used it. It allowed us to get a lot of quantitative behavioural data, especially as we could press more than one key at a time, so simultaneous recording of different fish was possible. This was a time before personal computers existed, let alone laptops or anything. The computer when I learned programming with Fortran at that time in Seewiesen, an IBM 1130, was a machine that was about three- or four-feet height and two feet deep, and it had a storage capacity of 8kb. You could only apply your programs using punched cards. When you had developed a program to run on the computer, you had to stack a pile of punched cards and on each punched card there was one command. So, when you had a program with say 40-50 commands, or perhaps 200, you had quite a pile of punched cards to feed into the machine. And then you typically found the program didn’t work. So, you had to find the punched card with the faulty command. Completely amazing in comparison to what we can do with computers nowadays.
HS: On the paper tape, what you were doing was basically counting? You tap to count behaviour you are observing?
MT: Yes. we had roughly about 20-25 behaviours that we could distinguish. So, we were running the tape and whenever a behaviour occurred, we pressed the respective key. Fortunately, we could record two fish simultaneously after some training. The information about the behaviours, when they occurred and for how long, and also the respective responses of other fish to these behaviours could then be analysed with help of the computer.
HS: What about in the field? Were you recording behaviour underwater as well?
MT: Yes, of course, but only on PVC slides. We didn’t have any electronic way to record data. You have a white board – a PVC slide – and a soft pencil and you can write on that and clean the plate after transferring the data to a (analogue) notebook. To make quantitative recordings, you draw a table on the plate before diving with the behaviours you expect to observe. When you do these observations, you should not put your eyes away from the fish that you are observing, because you lose them very easily. So, whatever you note down, you note down blindly; you don’t see what you write, you only need to know where to make ticks or write numbers onto your plate.
HS: And all this is happening under water?
MT: Yes, all this is happening under water.
HS: Things have really changed.
MT: Yes of course, things have changed a lot!
HS: Any other memories about the lab work?
MT: The memories I have is that it was extremely time consuming. With the maintenance and the observations, we probably spent between eight and 12 hours a day in the aquarium. And then we had to transfer data and all these sorts of things. We had times of very little sleep. It was truly laborious. But it was so fascinating that we didn’t mind really. We were so happy about being able to do this work, to obtain information about this intriguing system. We did a lot of different experiments to find out the major potential costs and benefits that drive that system, or in other words which could be important for the evolution of such a system. And, looking back at the paper now… also, the publication policy has changed greatly. This paper probably would have been split up into at least four different papers, if it were published nowadays, because of the completely different questions, and also the completely different experiments, as well as the combination of field data and experimental lab data and things like that. So, it is perhaps a rather copious paper in comparison to what is usually published in behavioural sciences nowadays.
HS: And did it help to know that your partner was also working on the same topic? Can you talk a little bit about that?
MT: Of course, this helped enormously. The possibility that we both could work on these fish, and interact and share the work, also the maintenance and practical work with the fish, helped enormously. And also, the field work, neither of us could have done it alone. So, to be able to collaborate when studying these fish was absolutely magnificent.
HS: Do you have a sense of how your understanding of what was happening evolved? Was it something when you started seeing how this was working? Was it something that happened gradually? Was there like a moment when you figured things out?
MT: That’s an interesting question. Our understanding of the system developed gradually during those years of observing the fish. It did not come in large steps but rather incrementally because of the different experiments we did. But interestingly, I still remember vividly that while sitting there and recording – and everything was tiring more or less, also often nothing interesting happened for a while – during these times, I always developed ideas and hypotheses about how to explain that system, how to explain the response to that particular treatment that we just had provided to the fish. And these ideas often varied between different days. So, this was not consistent. But with new observations, I revised my hypotheses or predictions, and so my ideas gradually developed into a picture that got more and more, I would say, consistent in a way.
HS: Were all the hypotheses that have been tested in the paper planned out from the beginning? Or did they evolve gradually as you were doing the experiments?
MT: We had a program at the beginning. And we were following that program, as far as we could, and as far as it seemed to make sense. But when you do such a study, you learn new things, you get new ideas, and you understand things that you did not know before. That then causes the need for modifying experiments or doing other experiments or new experiments that you had not thought of in the beginning. Also, you read more literature and you get more input from others. And so, it’s developing. In the end, you have something that is quite different from your plans in the beginning. It was quite a comprehensive study.
HS: How are the figures made for the paper? Do you remember?
MT: Yes, that was a bit special because before computers, before plotters and printers, everything had to be done by hand. This is the reason why we had an employee in our department who was only responsible for scientific drawings. She did this on a drawing board and with ink and ruler, etc. We made drafts on scrap paper to illustrate how we thought it should be and gave her the respective numbers, and then she would draw the graphs on grid paper. Subsequently this was transferred to transparent white paper before it was photographed. The photo prints were then produced in the department’s darkroom.
HS: Do you remember this person’s name?
MT: Barbara Knauer.
HS: I wanted to go over the acknowledgements, to find out a bit more about the people you thank here. The first two names are, of course, Dominique Limberger and Wolfgang Wickler. Talk a little bit about Wolfgang Wickler’s involvement with the work.
MT: This was also quite different from how nowadays PhD students are supervised. I think I had only one personal meeting with Wolfgang Wickler during the entire five years of my research to discuss my thesis with him, and this was not extensive or very specific. But his way to supervise these studies was actually quite efficient. The arrangement in Wickler’s department was that the entire group, including all technical and scientific staff, and all students working there, would meet after lunch for about an hour for discussions every weekday. At these meetings tea was served and people were expected to present their current work and to discuss interesting studies they found in the literature, and things like that. This was basically our supervision. We were expected to present our progress and data every perhaps three, four or five months, which were then discussed with the whole group, not just with Wickler specifically. And this was really quite good. Because, when other people were presenting their work and when discussions were revolving around themes that we found interesting and which somehow also related to our own work, we got a very broad overview of questions of general interest in the context of our own work.
HS: What other kinds of work were happening?
MT: There were these geese projects with bar-headed geese revolving around brood care and bonding. Then there were two more fish projects of PhD students who studied mating behaviour and sex roles in cichlids. A post-doctoral researcher was working in Kenya where he did only field work, but he reported about his work whenever he was back at Seewiesen. He was studying cooperatively breeding birds, pied kingfishers. Quite important work for the field at that time. Another researcher studied fur seals in the Galapagos Islands, who also regularly reported about his work. And one scientist worked on reef fish in the Red Sea in Israel, who also reported about his work. For the practical, empirical work that was done at our department, it was only these three fish projects and the work on the bar-headed geese at that time.
HS: There’s a long list of names. Let me just read them out to you. Andrea, Barbara, Eva, Friedericke, Ilse, Moni, Monika, Natalie, Tom, and Rick, and my full sibling, Andi. Who are all of these people?
MT: They were students from the University of Munich whom we were supervising for internships. They were also helping to collect data for some short periods of time during this practical training.
HS: And Andi…?
MT: She is my sister. I was actually surprised to see her name when reading the acknowledgements again, because I didn’t remember that Andi was helping us with this study. In any case, she was helping us in the field in another study I did after the PhD.
HS: It’s also interesting how you have written the acknowledgments in the language of cooperation and fish behaviour. Jürg Lamprecht, is that the….
MT: Yes, Jürg Lamprecht was the scientist who did the work on the barheaded geese. He was our first supervisor for this internship when we worked as ‘Goose Girls”, as they were called at that time.
HS: And Ulrich Reyer?
MT: Ulrich Reyer was the researcher working in Kenya on the Kingfishers.
HS: You thank both of them for yielding valuable computer memes. Do you remember what that is?
MT: Yes. Computer programs help you with data analysis. As I said, we had to program our analyses by ourselves. Uli had much more expertise in statistical analyses and I programmed a relatively complex factor analysis on the central computer in Seewiesen, which I could use and modify for my own analysis.
HS: It’s interesting you call it memes!
MT: According to the terminology of Dawkins from his book on the Extended Phenotype, or already in The Selfish Gene, he talks about ‘memes’ as units of information in comparison to ‘genes’ as units of genetic encoding.
HS: And then you say the English was adapted by Mrs. Phyllis Rechten and, Ms. Lesley Gardiner.
MT: Mrs. Rechten was the mother of another PhD student who studied cichlids in Seewiesen. She was a professional translator and was very helpful. And Lesley was the wife of a colleague who was working on spiders. This couple came towards the end of our study. Lesley was British, so she was a native English speaker and also helped with the English. Actually, when we first distributed our papers to our colleagues in Seewiesen and got them back with comments, which was after Mrs. Rechten had already corrected the English, I was, extremely disappointed because of the many corrections that our colleagues had proposed. When you think a manuscript is more or less ready for submission to a journal and then it feels like you must start from scratch – this is an important lesson to learn!
HS: But at that time, was it already the norm to submit to an English journal?
MT: No, it was not the norm in German speaking countries. But as this was a Max Planck Institute, they were a bit advanced in comparison to most universities at that time. Researchers there saw it as an important aspect. Wickler himself published about half of his papers and books in German, so he was not so extremely focused on publishing in English. For the others in the group it was quite clear that you should publish in English journals, otherwise your work would not be recognized.
HS: Some other names…Catie Rechten?
MT: She was a PhD student and the daughter of Phyllis Rechten.
HS: And then Fritz Trillmich?
MT: Fritz Trillmich was the researcher working on fur seals in the Galapagos.
HS: “In the field, families Brichard, Feldmann and Schreyen…”
MT: Brichard was the fish exporter, Schreyen was his son-in-law and his daughter also adopted the name Schreyen. When Brichard retired, they took over the fish export business. Frau Feldmann was a woman we met who helped us nicely in the beginning in Bujumbura when we didn’t have a place to stay. She was German but lived in Bujumbura since long and was very interested in what we were doing and helped us with practical issues.
HS: And there’s an acronym SUPOBU. How did they help?
MT: This was the fish processing company where we could stay during our field work.
HS: Okay, because you said they cared for our survival.
MT: Yes, they hosted us.
HS: And Dr. Ohlenschlegel?
MT: Dr. Ohlenschlegel was a fish veterinary biologist in Munich. When you keep fish in large numbers at times you get problems with diseases, and then we had the fish analysed by him to find out what the reason was and how to treat them properly.
HS: Do you remember whether there was any discussion around which journal to submit? Was Animal Behavior the obvious choice at that point?
MT: I think it was the obvious choice. Wickler was the editor of a behavioural journal at that time that was called Zeitschrift fur Tierpsychologie, a German title, which was also quite well reputed in the English-speaking world. At that time it already published many English papers, but also German ones. I wanted to publish in a different journal to get more international interest and attention to the paper. Animal Behavior was the leading behavioural journal at the time, Behavioral Ecology did not yet exist. And so, I tried it there.
HS: This paper is single authored. I was wondering whether there was any discussion about either Wickler or Dominique being authors on the paper. I also realized speaking to other people that the culture in scientific publication has changed quite a bit that, at that point, it was quite common for PhD students to publish on their own.
MT: Wickler, I think, would not really have been an adequate co-author because of his style of supervision, with his personal supervision being close to zero. Of course he provided resources, but that did not seem sufficient for co-authorship. And Dominique would have been a possibility, but we decided to publish our papers separately, which I think is also not such a bad idea. We were both working on the same species, we were collaborating, so when you publish together in all the papers, it is difficult to distinguish who did what. So, we said we really focus on our own projects. Of course we also published a paper together on our joint field work, but the experiments we did on our own we published separately, without mutual co-authorship.
HS: Do you remember anything about the peer review?
MT: I think it was not too harsh. Probably because of the very severe process of revising the paper based on the comments of the colleagues at Seewiesen before.
HS: I want to read out what to me seem like the major findings from the paper and I wanted your thoughts on them today: “Three factors proved to be of major importance in the cost-benefit analysis of helping as opposed to leaving for family-independent non-reproductive aggregations. Due to investment and to their rank within a family’s hierarchy, helpers grow at a slower rate than non-helpers. This cost is compensated for by (i) a lower mortality risk to helpers caused by their access to a defended shelter and by protection afforded by bigger family members, and (ii) a positive contribution by helpers to the future reproductive success of their parents: females with helpers produce bigger clutches and consequently more free-swimming fry (= siblings).”
MT: I think that for first time it was experimentally shown that there are costs to helping. This was an advance. Also other fitness correlates, like the increased reproductive output of breeders by the action of helpers in an experimental setup, had previously not been shown. Even in the meantime, not much more experimental evidence has accumulated in that direction because of the difficulty to manipulate the ecology and social system, especially in birds and mammals. And the third aspect, the benefit of gaining protection, is perhaps something that is quite specific for this system. Nevertheless, I think the importance of gaining protection in such groups is still underestimated in other systems because of the difficulty of getting the right kind of data. In cooperatively breeding birds, the observations happen mainly at and around the nests. Because when a bird flies away, it’s difficult to be followed. So, little is known about defence of the territory and the risk from predators except in the context of the nest itself. And nest predation is something different from predation on adults or on helpers. Hence there’s very little information about the importance of this factor. There are some recent studies indicating that predation risk may be really an important factor alsoin cooperatively breeding birds. But in fish it is absolutely clear. During my thesis work I performed the crucial experiments. We tested the survival of helpers against individuals that were in a group lacking large breeders to defend the group, which yielded a very clear difference in survival. And this was mainly due to the efficient defence of the breeders, which keep the predators at bay. We have accumulated a lot of additional evidence in the meantime, also from the field, that predation is the ecological factor that has caused the system to evolve in its actual form. It has become clear that outside of groups these fish cannot survive. If you leave a group and you are not accepted by another group, you’re dead within hours. So, predation is really extremely important. Therefore, the major fitness effect for helpers, and this was identified already by my experiments, is that they are allowed to stay in the territory, which is defended by efficient large group members.
HS: Looking at your research over the years, a thread running through it is cooperative breeding, and also studying fishes. At the time when you finished your PhD. was it clear to you that you want to continue studying cooperative breeding in fishes?
MT: No, the opposite was true. I really wanted to do something else, to have a change. And I wanted to study other animals, not only fish. I was not sure whether it should be birds or mammals, I could not really decide. And I ended up studying kiwis, which is sort of something in between!
HS: But you knew, it would be cooperative breeding?
MT: No, not cooperative breeding either. It was about the importance of the mating system for parental investment. But after some years studying kiwis, which was really difficult – a pure field study on nocturnal and shy animals that involved very hard work and which meant it was very difficult to get quantitative data – I realized how great the cooperative cichlid system was where I could do all these experiments under controlled conditions. And in the meanwhile I had switched to Vienna to a different Institute, where I started to do experiments with the fish again with my PhD and Masters students. So, I got back to the cichlids after some break.
HS: So, would you say that you followed up on your PhD? Were there questions that emerged from your PhD?
MT: Of course. We developed that further. We started with what we had obtained through my PhD studies and started over to continue answering questions that were still not answered at that time.
HS: Did you go back to Africa anytime?
MT: Yes of course but not to Burundi, because this was not possible as it was politically unstable. Too risky. So we went to Zambia, to the southern end of the lake, which Brichard actually had recommended to us already in 1978. He said, when you want to do observations, also because of the clarity of the water, better go to Zambia. And since ’95, we go there almost every year.
HS: Even till today?
MT: Not during the pandemic. So, the last time I was there was 2019.
HS: You have students who work there?
MT: Yes, we usually go there with students and postdocs, whoever is available. And they stay longer than I can. Now I’m retired, so I can probably stay longer in the future. But at that time, I could typically stay only between four and six weeks, while my group stayed usually for three months or so.
HS: Have you been back to the place where you did the fieldwork for this study, after the PhD?
MT: No, I have only been to Zambia and Tanzania afterwards.
HS: One of the things you start describing in the discussion is about the question of how useful studying adaptation in the lab is, to understand what’s happening in the wild. And you listed a few points justifying that might be useful. Over the years has your thinking on that changed?
MT: No. I am convinced that in that system, and in many others also, it is extremely useful to combine lab and field work. But I really would like to emphasize it is the combination that is important. Field situations, especially with regard to interactions with other species, the food source, water conditions that may be changing throughout the year, and also the large social interactions between different groups cannot be fully staged in an aquarium. We had wonderful large aquaria of several thousand litres, a huge circular tank with really great opportunities to do experimental work. And we have seen the natural conditions. But still, there’s a difference when you have a system that has evolved and developed without any human influence. You need that information. And if you have this information, you can construct situations that are similar with regard to the particular question that you’re asking. And then, in the aquarium, you have the possibility to manipulate everything, you have everything in your hand in a way. And the nice thing with these fish is that you can even manipulate the composition of the groups, because as we know from the field, this reflects the natural situation as these groups are very dynamic in their composition. New group members turn up and the individuals interact between different groups, visit other groups and may change between groups. We have a paper that will come out next week in Science Advances that combines all that information on long-term marked individuals, which we have followed for several years in the lake. From this extensive field work we now know many things that I had thought about and partly understood in my lab study forty years ago. Now we have the data from the field and we can confirm what we had partly concluded already from our experimental studies in the lab.
HS: Is this one of your most favourite papers?
MT: Yes, I think for me it is one of the most important papers. Because on the one hand, it was at the beginning of my career, but also because I think it has a lot of information that at that time was really novel to the field and which continued to be important for a long time. And people are still using this paper for answers to questions about the evolution of cooperative breeding. One of the nicest compliments I ever got was when Nick Davies, an eminent colleague in Cambridge, read this paper and wrote that it is so nice to see that someone has not only asked the relevant questions, but also done the right kind of experiments.
HS: What might be a reason for someone to read the paper today?
MT: I think the results on the importance of predation risk, the costs of being helpful and also on the productivity effects of helpers are still quite unique, as they were obtained by controlled experiments and not just correlative information. This allowed us to exclude alternative hypotheses and explanations by controlling for confounding variables.
HS: Is there anything else that you’d like to add that haven’t been covered by the questions that I asked?
MT: I think one thing that this paper has only partly dealt with, which turned out to be really, really important for explaining this system, is what we call pay-to-stay or the trading of commodities. I mentioned this as a likely explanation for the relationship between breeders and large helpers at the end of the paper, where I refer to a follow-up manuscript published in Behaviour a year later. In that paper I reported experiments that target this particular aspect: Individuals that stay in the territory of dominant breeders have to provide some service so that they are allowed to stay. It turns out now, through the many years and numerous studies with different collaborators, that this is really how you can explain that unrelated large helpers show a lot of investment in these groups, because the dominant breeders make them work. They really put pressure on them. And if they don’t respond appropriately, they are punished. We have another paper of which I’ve just read the proofs today, which will come out in a few weeks in Behavioral Ecology, where we show by quite an elaborate experimental series that when you prevent helpers from caring for the eggs of breeders and you allow the latter to punish the helpers afterwards, then the helpers that were experimentally made idle increase their helping effort in response to being attacked. When you prevent the breeders to punish lazy helpers, then they don’t show this response. So, it is really a kind of negotiation about how much is required from me as an investment for the benefit of the breeders with whom I am not related. In other words, I’m only working because the dominants enforce me to. But the benefit I get in return is group membership, which means I can survive. If I have to leave and if I don’t find another group, then I’m very likely dead within a short time. So, it’s this kind of what we call trading of different currencies or commodities.
Reflections on Papers Past 
