In a paper published in Ecological Monographs in 1976, Bernd Heinrich demonstrated, through careful observation and experiment on marked individuals, how bumblebees develop specialization in their foraging at the individual level, and examined the costs and benefits of of specialization through comparisons with other bee species. Forty years after the paper was published, I spoke to Bernd Heinrich about his motivation for carrying out this study, memories of field work, and the connections between his studies on bees and subsequent work on ravens.
Citation: Heinrich, B. (1976). The foraging specializations of individual bumblebees. Ecological monographs, 46(2), 105-128.
Date of interview: 10th September 2016 (via Skype)
Hari Sridhar: To start I wanted to ask you about your motivation for doing this particular piece of work. By looking at your publication profile, I realized that your first publication on bees was in 1972. And then you published quite a number of papers on bee energetics and physiology. What was the motivation for this particular piece of work , in relation to all that you had done on bees before that?
Bernd Heinrich: Well, it’s kind of a long story. I had always been interested in bees since I was a young boy. Here in the Maine woods, I used to line bees and find wild bee trees. And I got interested in bee communication, in the honey bees, the Von Frisch stuff. I had this little book on the dancing bees But research-wise, I came to bees actually via my thesis at UCLA, which was on sphinx moths winter temperature regulation. So, I was interested in mechanisms of body temperature regulation in insects and that was my main drive. In the moths, I discovered a new mechanism actually of regulation of body temperature in insects, and so I wanted to go compare it other insects. So I started working with bumblebees, and there were connections in physiology but also differences. And then I found out that that a lot of this temperature regulation depended on behaviour. So I worked with different behaviours, such as bumblebee incubation of their brood. And when they foraged out in the field I was looking at their behaviour on different kinds of flowers and found that they had different body temperatures. That then related to the foraging behaviour – some bees would be foraging on one kind of flower and had certain energy costs and benefits, and that varied between different flowers. So that’s how I got interested in the foraging behaviour of bees, in different kinds of flowers.
HS: Take us back to the time when you did this study – July to September ‘73, and then again June to August ‘74. What was your daily routine, at this time, when you were doing these observations and these experiments?
BH: Well, at that time, I was in the entomology department at University of California Berkeley. But my home was here on the other side of the continent, in the East, in Maine, where I grew up. This is where I was doing the field work, right here at our farm. I don’t know if this answered your question. But yeah, it was here that I would come back home in the summertime. I remember, I think just before this I had a paper in Science on body temperatures in bees. I was grabbing and stabbing bees on Epilobium flowers and found that they regulated very high temperature, and it kind of took off from here.
HS: Were all the places where you did the observations in and around you around your farm?
BH: Yes.
HS: Typically, how many hours in a day would you be out in the field doing these experiments?
BH: Pretty much all day long. Yeah, I spen tall the time here. That’s pretty much what I did. And I got totally involved with it and took a lot of time. I was just looking at my paper; you had sent a copy of it to me. I hadn’t seen it for forever. And I didn’t realize I had marked so many bees. I had no idea it was that involved, but it certainly took up pretty much all of my time.
HS: And in the intervening period were you back in the University of California?
BH: Yes, I would come up early summer and go back in the fall. When I got back I would, you know, work on writing the paper. I don’t remember doing any writing in Maine. I only tried to collate the data there. And you wondered how long it would take me to write – I have no idea at this point how long that took. But I had a research position at University of California and my teaching load was fairly light. I was only teaching one course, on insect physiology. So I had plenty of time to write,and that’s where I did it.
HS: You thank a person by the name of Patty Mudge for assistance in the field. Tell us a little more about who this person was and how she helped.
BH: Well, actually, I don’t know too much now.All I know is Patti Mudge was a high school student.She was a daughter of a friend of my father’s – Dr. Mudge at the nearby University. She and a friend of hers, Pam Deringus, helped sampling flower nectars and also we did a foraging behavior project in a tabletop arena, where we tasted individual bumblebees’ learning speed to specialize on blue vs. white colors. They could be trained to either, but learned blue quicker. More bumblebee flowers are blue than white.
I thank my parents for providing facilities. I was basically staying at the farm that with my parents.
HS: I’m just going to read a couple of lines from your paper. You say “Observations were made in Franklin County, Maine in the vicinity of Dryden, Farmington, and Livermore Falls. The area contains forests, undisturbed bogs, and farmland.”How much has this area changed in the last 40 years? If you compare to then, what are the major changes that have happened here?
BH: Well, I’m living right here now, at exactly the same place. And it’s pretty much the same, except it’s a little more settled. I had a specific ecological study area – this undisturbed bog. I made that my wild study area for native plants, and that was kind of sampled for my book Bumblebee Economics, and that’s still there, exactly the way it is. The fields are still there like that. The difference is the bumblebees. There seem to be hugely fewer bumblebees, I don’t know why, but it’s kind of disturbing.
HS: Has that been a continuous gradual decline or has it happened suddenly?
BH: I would say I’ve noticed it for a long time. I have in my mind the images of all of these bees, all of these different species, and some of them I have not seen at all. For a long time, I didn’t look at bees at all; I was working with ravens for many years. So I wasn’t really paying attention to bees. But now that I’m not studying ravens anymore, you know, and I’m living out here in the woods, in the fields, and can see the bees, I’m looking at them again. This year, for example, I saw quite a few queens in the spring and I tried to see what species, but then later on there were very few.
HS: What about the other species of bees you recorded? Have they also declined?
BH: The bumblebees are the most conspicuous ones; there are a number of species – about half a dozen or so. I wish I could have, but I never kept track of the individual species of the solitary ones. I didn’t even know their names. So I really can’t address that.
HS: Has the plant community changed?
BH: No, the plant community is still the same.
HS: And do you continue to do research in this area, either on bees or on other topics?
BH: Yes, I’m, doing field research. I’m Emeritus from the University of Vermont. I came back east to be here, nearby, in Vermont. I wanted to get a job at University of Maine, but it didn’t have an opening at the time. So, I went to Vermont, which is close,and I know well. I had been involved with ravens for about 20-25 years and I’m now picking up on all kinds of other things,which I pick up from familiarity. At the moment, I’m kind of involved with some burying beetles. And I was working with different kinds of birds.
HS: Do you plan to restart the research on bees, now that you’re back in this place?
BH: I don’t have any plans to work with bees. Actually, right now, if I did, it would be very, very difficult because there just isn’t enough around for me to do research with. So I considered myself very fortunate to have had the opportunity when they were around. So I basically go by what’s available and I’m interested in just about any behaviour. Whatever catches my eye, that’s what I go for. I don’t care if it’s bees or beetles or birds.
HS: I then wanted to ask you about the figures and the illustrations in this paper.Do you remember how you made the figures for this paper?
BH: Well, they look a lot like my photographs, so I’m sure I did them from my photographs. I did a lot of photography.
HS: The illustrations of the bees you mean?
BH: Yes. All my illustrations are my own in the books except the first book –Bumblebee Economics, for which I had somebody do illustrations. But since then I’ve done all – I do watercolours, pencil drawings and ink drawings.I use photographs.
HS: They’re really beautiful. I just have a black and white scan of the paper, but even in this the visuals are really striking.
BH: Well, thank you.
HS: What about the graphs? Would you remember if they were all hand-drawn at that time?
BH: I’m pretty sure hand-drawn. Yeah, I did hand-draw. I hand-lettered too, with a Leroy lettering set.
HS: Did this paper have a relatively easy right through peer review?Was Ecological Monographs the first place it was submitted to?
BH: I’m pretty sure, yeah. This is a fairly long paper,and that’s where I would have submitted it. And it was accepted there. I’m pretty sure, I did not send it anywhere else.
HS: I know it’s a really long time ago, but would you remember if it had an easy ride through peer-review?
BH: I think so. I don’t remember the problems.
HS: At the time when the paper came out,do you recall what kind of attention it received, within academia and from the popular press?
BH: Certainly, nothing from the popular press. I don’t know anything about any attention I wouldn’t have paid any attention if there was, but I didn’t remember any attention whatsoever now.
HS: Over the years, it’s been cited many times.Do you know what the paper mostly get cited for?
BH: I have not the slightest idea. I would not be interested if it’s cited or not or for what. I did it and there’s nothing I could do about it anymore. But it did influence me in the sense that I continued on with other studies. As a matter of fact, when you first contacted me, I thought this was about another paper, which is one that I remember a lot more thoroughly, which came three years after this, where I followed up from this one. And that one was published also in Ecology, and it was called “ “Majoring” and “Minoring” by Foraging Bumblebees – an experimental analysis”. And this is what I remember more. I don’t remember this one in Ecological Monographs much at all.
HS: Do you know why you remember that one better? Is it because the results were more striking?
BH: Yeah,Because one of the major questions remaining from Ecological Monographs, as far as I remember, was I found all of these bees with individual specializations. They definitely had preferences. And so you know, I wondered for a long time, here are many species and some of it you can explain by species differences, but then the same species have differences as well. So I decided what I really needed to do is find out how come you get these individual differences? I think the Ecology paper says more because it explains it. And what I did there was work with one species Bombas vagans, which was one of the most common ones, and I had one colony in a box with an entrance, a round hole,which I could close with a cork stopper. Anyway, what I did was mark all of the individuals in that colony – a small colony. I had the colony in an enclosure, like a surrogate field, screen wired, where there were caged, I would put the flowers in there, in pots, and then all the bees were marked and let out one at a time. And afterward I would plug it back up there and wait till they get back, anyway. So I got the whole foraging trip confined in that area and to different flowers. And I found that basically the bees, when they start out, they sample just about everything around, then they quickly start to specialize. That one had more appeal to me because it was experimental. And I could see the origins of the behaviours.
HS: Can you tell us a little bit about motivation for the book – Bumblebee Economics – and how that came about?
BH: Well,I felt that there were so many interesting stories in these bees. I had worked, first of all, on the physiology of temperature regulation, and looked at temperature regulation in the field, and seen how it’s connected with nectar, with kinds of flowers, and with flower evolution. So I wanted to put it into one story, with respect to the natural environment where I had my study area – the bog – and kind of put it into context. Otherwise, it just seemed kind of just strewn all over the place. That was the motivation to write this paper.
HS: Today, it’s 40 years since this paper was published. Would you say that the main conclusions of this paper still hold true, more or less?
BH: More than more or less; I don’t see why it should be any different. No reason to think it’s any different.
HS: Is this a literature that you still sort of keep on top of the literature on – bee energetics, foraging and physiology?
BH: No, I don’t; I see papers once in a while. And it seems to me there’s another wrinkle here or there. I basically stopped because I had answered all the questions that I had. There might be other little questions too, but they weren’t big enough for me to watch.
HS: Why did you switch from studying bees to studying ravens?
BH: Well, actually, interesting you should ask that, because it is related. It’s because of my work with bees. If it hadn’t been for the bees, I would never have worked with the ravens. I had, you know, early childhood experience with corvids as I had with bees. I just loved crows and ravens. And, again, here,at the site I’m sitting in right now, in Weld, Maine, 10 miles away from where I did the bumblebee work – I described it in Ravens in Winter, how I got started – I heard ravens making a lot of noise,and I said, “Well, they shouldn’t be doing an advertisement, etc.” And I knew there’s something there and I went there. So it’s from the point of evolutionary questions of foraging behaviour, for which I’d gotten into and looked at the differences, for example, between honey bees and solitary bees and bumblebees. I just switched to looking at foraging behaviour in a bird.
HS: Have you ever read this paper after it was published?
BH: Never. I have not re-read. As I said, I remember the one in Ecology – the majoring and minoring experiments – better. The Ecological Monographs, because it was so many different things, and the data left so many questions in my mind- What the hell was going on – it didn’t give any great Aha experience. It just kind of brought some data on what I kind of expected but I didn’t have any data on.So it set it up for the majoring and minoring one.
HS: Would you count this as one of your favourite papers, among all the papers you’ve written?
BH: Well, like I said, the majoring and minoring one is definitely one of my favourites, because, for one thing, it’s got such a close analogy with what I did with the ravens. I did exactly the same thing with ravens, as I did with bumblebees. I had the ravens in the huge, huge enclosure and marked them and saw that the individuals were interested in and sampled all sorts of the visually-conspicuous items, to then eventually seek out specifically those that provided them food(as bumblebees did with the different kinds of flowers) . The symmetry is the sampling and the finding the goods by individual initiative. (It could then potentially benefit others, if it was communicated, and I did of course then pursue that question in ravens).
HS: You said you don’t read the papers you’ve written before. What about the books? Have you ever gone back to reading the books you’ve written?
BH: No, I have not. I feel that someday I would like to. But the thing is, I’m always involved in writing another one. I don’t have much time.
HS: Do you notice any striking differences between the way you wrote then and the way you write now?
BH: Well, It seems very detailed to me,. Now, at least right now, I’m doing small research projects, and they’re much more narrowly focused. They are compartmentalised – here is one little problem, here is another little problem. But as I was going into this with bumble bees, there was so little known and there was much more scope. Gradually, problems become smaller; more specific. But as far as the writing is concerned, I don’t know, I basically do the same thing, but maybe at a smaller scale.
HS: If you were to redo this study or the majoring-minoring experiments today, would you do them differently?
BH: No, if I were gonna redo the same thing, I would do the same thing. I liked what I did, for what I wanted to find out. Obviously if I had a different question, it might require different technology, but this one didn’t require too much technology. It required me being out there, being there all the time, because once you start something, you can’t just drop it in the middle. I had to be out and checking on it every day, those bees. It’s not technology, it’s just simply perseverance and looking closely. And that’s the same always, and it’s the same with me right now.
With the ravens the technology was a lot different. For example, to track them, I had radio tracking – so I had to put radio transmitters on them and be out there with radio receivers and driving around the countryside picking up signals and that kind of thing. So it involved different technology, but it was again following individuals,
HS: What would you say to a student who’s about to read this paper today? What should he or she take away from this paper? And would you add any caveats for them to keep in mind when they’re reading this paper?
BH: Wow. What should a student take away from the paper? Well, I think, I would recommend, and, you know, hope that the student would notice, that it’s direct contact with the animals in the field – continuous contact – and that it’s important to watch individuals and get as much data as you can on many different aspects of everything that impinges on the animal. In other words, what were they getting from the flowers and where were they going and all the little details, because in the end, everything connects with everything else. And just to be careful in trying to see as much as possible, because you never know – little things make a big difference. I was out there looking at everything I could see, and recording as much data as possible, and I wasn’t really certain yet how it would all fit together. Some data you start and it keeps growing; other data, it doesn’t So it’s always kind of an experiment to see how it goes. But in terms of results and conclusions -I think they’re pretty obvious. I wouldn’t have to tell them anything. Just look at the results and the interpretation isn’t that difficult.
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