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  • Post date: 1 year 9 months ago
    Citation for this post: BibTeX | RIS

    This post was contributed by Christina Birnbaum, a postdoc at Murdoch University, Western Australia. Find out more about what she does by visiting her website

    was held this year in Pirenópolis, Brazil. Thanks to the IAVS Global Sponsorship Committee who provided me with a generous travel award, I was able to attend the conference and take part in one of my favourite association’s annual meeting.

    The conference took place in the heart of the Brazilian savanna (cerrado) country, a town 150 km west from the capital Brasilia, with a population ~24 000 people and surrounded by about 400 waterfalls, or so I was told. Pirenópolis, named for its location in the Pireneus Mountains has a very rich ecological, historical and artistic heritage and was an excellent location for the IAVS conference, in my opinion. 177 delegates, of whom 48% were Brazilian, participated in the annual meeting in Pirenópolis.

    The topic of the conference this year was Conservation of Plant Communities: From Environmental Drivers to Ecosystem Services opened the conference with a great introduction to the cerrado and it ecology by giving a talk titled “Cerrado ecology, ecosystem services and management decisions”. In her talk, Giselda Durigan warned that cerrado biodiversity is currently facing many threats, e.g., fragmentation, biological invasions, inadequate fire management and most recently, afforestation programs for carbon sequestration that must be addressed if we were to preserve these unique ecosystems.

    I particularly enjoyed the plenary by on “Conservation challenges in savannah/forest mosaics” where he gave an overview on the history of savannas and future challenges in the face of global climate change.  talked about “Invasions of tropical plant communities: fewer than those of elsewhere, or just less studied” where he argued against a widespread paradigm in invasion biology that tropical forests are relatively resistant to invasion due to their high species diversity. In fact, they are not resistant to invasion and require similar efforts for protection from invasive species as temperate regions.

    My personal research interests lie in plant-soil interactions and I was excited to see several talks on the topic by on using rhizotron in assessing root production in grasslands and forests, on plant competition and soil microbial communities and on arbuscular mycorrhizal fungal community diversity in relation to altitude in the Himalayas.

    met briefly as well during the conference to welcome new members and discuss future directions. Among these, a need for a forum/platform for discussions was raised as well as encouragement for people to take advantage of the group and seek professional advice and/or help with English language editing from English native speakers.

    ran a session on social media and communication in science and this opened up the floor for discussion on the usefulness (or not) of social media in promoting one’s science. To my surprise, very few people were live tweeting during the conference.

    The conference ended with a heart-warming tribute to as presented by .

    For me, conferences are as much about science as they are about meeting old and making new friends and colleagues, and learning something new about the local nature and the challenges it may be facing.  Next 60th IAVS annual meeting will be held in Sicily, Italy. I strongly encourage everyone interested in vegetation science to attend!

  • Post date: 1 year 9 months ago
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    Ed note: This is a guest post by  on a global initiative to study decomposition in diverse systems. 

    Globally, about 2700 tons of carbon are stored in the soil, which is 2-3 times as much as in the atmosphere. Therefore, changes in the decomposing activities of soil organisms may have large implications for the concentration of the greenhouse gas carbon dioxide (CO2) in the atmosphere, as during decomposition, soil carbon is converted to CO2. 

    Tea bags, Photo by Judith Sarneel

    Therefore, there is great interest in testing the effects of climate and climate change on decomposition. Many decomposition studies have been carried out, but as each researcher chooses her own method it is difficult to compare data across studies. For example, it is difficult to filter out the effect of climate in decay curves obtained from litter incubated at 3 cm depth in Alaska vs litter from another species, buried 6 cm deep in South Africa? Furthermore, measuring decomposition is a quite laborious process. However, with the recently developed Tea Bag Index that uses tea bags as standardized litter bags, life has become much more easy, and decomposition can be measured in a standardized, highly comparable manner.

    The teatime4science project aims to collect global decomposition rates and create a global soil map for decomposition. We invite you to join our project.

    The Tea Bag Index experiment is easy: You take one green and one rooibos tea bag (everybody has to use the same brand). You weigh them, bury them 8 cm deep in the soil and after 3 months, you take them out, dry them and weigh them again. The weight loss will tell you how quickly plant material decomposes at the burial location.

    Litter mass loss over time of Rooibos and Green tea

    By using two types of tea we obtain two proxies that characterize two different phases of the decomposition process. During the first phase, all the easy material is consumed, while in the second phase, mass loss is much slower as only the more recalcitrant material is left. With the decay of easy-to-decompose green tea (green line) one can determine how much of the labile fraction of the material is decomposed and how much is stabilized, which is a proxy for the second phase of the decay model. Rooibos tea decomposes much more slowly (red line) and after three months, it is still in the first phase of decomposition, from which the initial decomposition rate (k) can be estimated.

    The TBI team members: Judith, Joost, Mariet and Taru Photo by Judith Sarneel

    Now we are on a mission! The mission is to get as many tea bags buried (and retrieved) as possible. So far, many researchers across the world have tested the method and we have received many positive reactions. We are in the process of running citizen scientist projects in several countries. More than 350 classes have joined the project, and each of them have had the opportunity to learn about the importance of soils and the processes that occur there.

    Do you want to join? Don’t hesitate, it’s fun! Just send an email to . You can join by burying a few bags or many bags (e.g. along side your own experiments), both are very welcome!

    If you want to bury a few bags, we can offer to send you tea.

    If you want to buy many bags with a large geographical spread, you can apply for co-authorship of our database and its analysis paper.

    You can contribute data this year and next year (2017).

    Stay updated via .

  • Post date: 1 year 9 months ago
    Citation for this post: BibTeX | RIS

    In 1984, Gerald Wilkinson published a paper in Nature showing that vampire bats share food in the form of regurgitated blood, within groups that contain both kin and non-kin. This was one of the first clear documentations of reciprocity in animals, and the paper went on to become a citation classic and a textbook example for reciprocal altruism. I spoke to Gerald Wilkinson about the making of this paper, and its impact and relevance in the relation to whats happened in the 32 years since it was published.

    Citation: Wilkinson, G.S., 1984. Reciprocal food sharing in the vampire bat. Nature, 308(5955), pp.181-184.

    Cited by 858 (source: Google Scholar on 1st July 2016)

    Date of interview: 15th June, 2016 (on Skype)


    Hari Sridhar: Did you go to Costa Rica with the intention of studying bats?

    Gerald Wilkinson: My initial trip to Costa Rica was as a student, as part of an Organisation for Tropical Studies field course. But at the same time, my advisor and his wife were also in Costa Rica, doing research on bats, and so I visited their site before the course for a couple of weeks. After the course, I got money from the OTS to stay another three months and continue a project that I dreamed up at the site where they were working. This was not on vampire bats but on a different kind of bat. I had this idea about fruit dispersal and group foraging in a little bat that both feeds on nectar and fruit. But these bats were very hard to study because they were very easily disturbed and would fly out of the roost whenever I tried to catch them. Vampire bats, on the other hand, were really common and very easy to work on. Around the same period of time - those three months - Jack Bradbury went to a regular bat meeting where he heard a German biologist - Uwe Schmidt - report that he saw vampire bats regurgitate blood to each other in his captive colony. Jack wrote me a letter and told me about that observation and said that, maybe, this might be something I wanted to think about. And so I actually began, at that time, trying to catch and band vampire bats, and then dreamed up the project that I subsequently did between '78 and ’83.


    HS: In the paper you say a “26-month (September 1978– February 1983) study”. Does the 26 months refer to the time you actually spent in Costa Rica?

    GS: Yes. There was the initial 3 month period after which I came back and wrote proposals to raise money for my work. So it was awhile before I was able to go back.  On the next trip, I stayed continuously for 9 months, came back to campus for 3 months and then went back and stayed for a full year. Finally, there was a fourth trip that was only six weeks. It was on that very last trip when I did the reciprocal feeding experiment with the captive bats.


    HS: Were you already registered for a PhD when you went to Costa Rica for the first time?

    GW:  Yes, it is pretty common in the US that students will first pick an advisor and then develop a research project after they start. And it varies, depending on the advisor, how independent these projects are - sometimes they are very close to what the advisor does, sometimes they are quite distant. We got money from the National Science Foundation (NSF) to support the project I did. Actually, money was given for two different projects – the vampire bats in Costa Rica and also for greater spear-nosed bats in Trinidad, which my advisor was going to do.


    HS: You also mention another grant – the NIH training grant – in your paper. What was that for?

    GW: That was a consequence of going to graduate school at University of California, San Diego (UCSD). They had - they may still have - one of the longest running training grants from the NIH, largely for genetics. So I was supposedly doing genetics! I was, in a sense - taking blood samples, doing allozyme electrophoresis, genotyping the animals, but I am sure I was the only person supported on that training grant who was doing field work. Everyone else was doing lab studies, of viruses and Drosophila and other more genetically tractable organisms


    HS: Did you start a PhD immediately after you finished your Bachelor’s? How old were you then?

    GW:  Yes, right after my Bachelor’s. I was 22 when I started my graduate work, 23 when I began doing that vampire bat work and 28 when I finished.


    HS: I’m intrigued by one aspect of your field work - “focal animal sampling within roosts”. These roosts were in tree hollows. How did you manage to observe these bats inside these hollows?

    GW: The trees were large. Most of them were Anacardium excelsum - a relative of cashew - and they tend to get very large hollows. Most of the hollows were big enough that I could go into the tree. One roost was in a silk cotton (Ceiba pentandra) tree that was so big that I could lie down completely inside the tree.

    HS: Inside the hollow?

    GW: Inside the hollow, yes. The diameter of the tree was about six feet inside, probably about 10 feet outside. So these were big trees. The bats would be at the top of the hollow, which, in most cases, was pretty high - probably twenty to thirty feet above where I was. So, I would actually lie on my back and observe them with binoculars. I tried to video record them with Super 8 mm film but that didn’t work very well. With a camera you are stuck in one location, but the bats move around a lot so I needed to move around too to keep track of them. We also had to wear respirators when making the observations. Histoplasmosis is a fungus that grows in bat guano, something I was very aware of and concerned about. So the students that helped me and I always wore these respirators. It was not easy. It was very tiring so I always had someone helping me. One person would call out observations and the other person would sit outside the tree and write them down.

    We also made little devices that would emit a click at set intervals of time, which we would listen for with earphones. I think for all the vampire work, I had set it to go off every 10 seconds. At every click we recorded whatever behaviour the bat was doing. I got the idea for this device from a primate field course I took as an undergraduate student at UC Davis. Davis is one of the eight places in the US that has a primate centre, where different species of monkeys or apes are kept in large outdoor enclosures. During that course we observed bonnet macaques in one such enclosure and recorded behaviours with the help of these clicking devices.

    You know, at the beginning I was not sure exactly what I was going to find. I just knew I needed to be systematic, be quantitative. I knew I wanted to study food sharing but I didn’t know how often I would see it, so it was done with some level of hope. The information from these focal animal samples was mainly used in a . The food-sharing was so infrequent that I recorded it whenever I saw it. It was so rare that if I had done it only on focal animals I would have had no data. In fact, in the first six months, I think I had seen it only a couple of times. At that point I was starting to think that the whole project was doomed. I think part of the issue was that – and this is not mentioned in any paper –in order to see the animals and identify them, I used coloured reflecting bands – bird bands, basically - on the wings of the bats. And to see the bands inside the tree I had to shine lights on them. Initially, the bats would always hide from the lights and so I couldn’t make any observations. In order to overcome that, I would, every single day, take a miner light into the tree and shine it on the bats continuously. These would last for 12 hours with rechargeable batteries, and the bats had nowhere to go, so in some time they got habituated to the lights. I could confirm this with a night vision scope which I could use with infra-red light. Infra-red light is invisible to bats. So when I compared their behaviour with the night vision scope and with the lights I couldn’t tell any difference. But it took months.


    HS: What were the bats feeding on?

    GW: The site where I worked was a cattle ranch, but the bats, actually, never fed on the cows. They fed, primarily, on the blood of horses. And I know that because we put radio-transmitters on the bats and tracked them out to the pastures. Vampire bats do feed on cows in other places but this particular population seemed to like horses more than cows.


    HS: You have acknowledged numerous people in the paper. Can you tell us a little about their roles?

    GW: Yes, I had several student assistants. Terry Lamp, Robin Weiss - it was kind of funny because we were often called Batman and Robin - and Michael Lee Jones. During the two long stints of field work, one or two of those three people were always with me.  And then in the final six week period a guy named Doug Bolger helped me. I think, all of them had just finished their undergraduate degrees, so it was kind of a break for them, before getting a job or going to graduate school. Actually, I’m not sure now, but maybe Michael had a little more experience. Maybe he even had a Master’s degree when he came to work with me.

    Anyone else who I have acknowledged read and commented on drafts of the paper. This included Mark Taper, who was my grad. student office mate, Robert Gibson who was a postdoc at that time in the lab, and my advisor Jack Bradbury.


    HS: If you don’t mind my asking – how come your advisor was not an author on the paper?

    GW: No, I don’t mind at all. Jack has an unusual attitude towards his graduate students, in that he would not insist on being a co-author on their papers. He would agree to be a co-author only if he thought that he had contributed an equal amount to the work.  In the case of this paper, he contributed to the writing, but I did all the work. In fact, those first two weeks before my OTS course was the only time we were ever in the field together.  So he had very little idea of what I was doing until after I had done it. But I did ask him to be a co-author, because in my mind, I would have never done what I did if it weren’t for his advice. But he said - you did it, you deserve it, you should take all the credit.


    HS: In your paper you also mention a personal communication from T. Fleming – “one pair of females marked by T. Fleming (personal communication) in 1970 roosted in the same area in 1981". Are you referring to ?

    GW: Yes, that’s Ted Fleming. Ted had previously worked at the exact same site that I was at, and he had banded vampire bats, so some of the bats that I caught were ones he had also caught and banded over 10 years earlier. So I used some of that information to age some of the animals that I had.


    HS: While you were doing this work, did you already get the sense that this was something big and important?

    GW: I was highly motivated to to look for reciprocal altruism. That was definitely in my mind from the beginning. But I did not know at all, until almost the very end, that I had found much of anything.  Even after we did the final experiment we did not know what we had found, because we didn’t analyse the data until we got back to San Diego. I was just randomly taking bats out and watching how they fed, and we were doing it all at night, and also doing other things at the same time, like radio tracking. So we were fully occupied in just doing field work and collecting the data. It was only afterwards that we said - Oh my goodness! Look at this!  And it was only at that point that I thought – Wow! This is actually pretty cool.

    I first sent that paper to Science but they said they didn’t want to review it. So then I sent it to Nature, who reviewed it but returned it and said they won’t accept it but would be interested in seeing another version – you know, that kind of standard letter.  Now that was one of the first papers I had submitted so I took that as a rejection. But people explained to me that it wasn’t being rejected outright and that there still was a chance.


    HS: At the time when you did this work, was the idea of reciprocal altruism topical in academia?

    GW: Yes definitely. came out in '71. I learned about Trivers’s work as an undergraduate at Davis. The guy I took the primate class from ran a graduate course on E.O. Wilson’s Sociobiology. That would have been 1975, I think. I learned about reciprocal altruism at that time and became interested. And then, around the time I started my work was when , which was one of the first claims of finding some kind of reciprocal altruism in the wild. That got a lot of interest initially but also many people were questioning it. So, I was really very motivated to work on cooperation and look for some kind of reciprocal system but I didn’t know the vampire bats would do that. At that time I sort of assumed it was all going to be kinship, but I was very keen to test the two.


    HS: I notice that you didn’t cite Trivers 1971 in your paper..

    GW: That’s interesting, I didn’t remember that. Nature only allowed a limited number of references. Yes, I think it was 20 max. But I can’t imagine I didn’t cite Trivers! Well, part of it was - this was much later - the came out and I think I cited that instead. But Trivers should have been cited, because the motivation for this study was prior to Axelrod and Hamilton. I mean I was already down there watching the vampire bats long before that paper came out. But once it came out it actually gave me the idea for using the censusing as a way to measure the opportunity for the bats to share food with each other. That came directly from Axelrod and Hamilton. They have this little variable called ‘w’ which is sort of the likelihood that a particular pair will find the same circumstance in the future. Sort of the opportunity for future reciprocation. Earlier, I had some other method I had come up with to contrast kin selection and reciprocity, but when I read their paper it was like – Aha! I could just use my census data to calculate association. It was fortuitous because I did not have a specific plan for the census data at the beginning, except that it seemed like a good way to quantify social organization.


    HS: Did the paper create a buzz when it was published?

    GW: Yes, I think so. Certainly, among all the people interested in reciprocal altruism. But it did not get a broader reach for a while, apart from some coverage in newspapers - the LA Times and the Boston globe, maybe the New York Times. But there were several subsequent things that happened that increased its visibility. I got invited to write a , which reaches a much wider audience, including schools and non-scientists. That piece then, I think, motivated a . Right after the Nature paper came out, Trivers wrote a book called – this was in 1985 - and he called me up and interviewed me in great detail about the study. And to me, his description of the study is still the best of any that I did not write. He obviously knows the topic and he seemed to really like the study. Even though I didn’t cite his paper! I am sure he must have asked me about it at the time. His must have been the first book to carry my work, but after that, for a while, it was put in essentially every animal behaviour book and a fair number of general biology books. For a period of time it became the feature example for reciprocity, or something other than kin selection, which is funny because it does involve kin! I think it is partly also because it is vampire bats – they are sort of mysterious and sensational. So it sort of snowballed after that. It’ll be interesting to go back and track its citations over time.


     HS: Were your findings and interpretations controversial when they were published?

    GW: No, I wouldn’t say they were controversial then. I can remember interviewing for a job at Cornell and having a long conversation with , who was sort of very pro kin selection. I had conversations with Bill Hamilton. After my PhD I went to Sussex, England for a post-doc. and during that time I went up to Oxford and gave a seminar on vampire bat food sharing and Bill Hamilton and Richard Dawkins were in the audience. Actually that’s the other thing I forgot to mention, I should have remembered this - probably the one thing that catapulted my study to fame more than anything else was, after listening to me at Oxford, Dawkins immediately realised that this was a good story, and included it as an example for tit-for-tat in the second edition of The Selfish Gene. The second edition, which came out in 1989, had huge readership so that really helped increase my study’s visibility.

    It became controversial later on, I think. At least people began openly doubting the story in various ways. In fact, - the first of several – was, in part, written to try to counter all of the claims that had been made. Back then I did think most of the criticisms were wrong, but I didn’t have a whole lot of data so I couldn’t rebut them. I could only say - I don’t think so. In some ways, Gerald really benefitted from the history of this research project. My story got a lot of attention, then people raised various doubts and over time even openly dismissing my findings. I know people who thought I must have been wrong. But now, given the data Gerald has collected, which is an order of magnitude more than I collected, we can show that the claims people were making were not correct. Explaining it all is still a bit of a challenge but I think the essence of the story in that paper is more or less correct.


    HS: Recently, you have gone back to studying vampire bats with your graduate student , but for a long time you had moved away from studying them. Why was that?

    GW: Well, when I finished my PhD I had just spent 26 months of a five year period living largely by myself in the tropics, with not a lot of intellectual interaction. At that point, I decided that this was not a good strategy in the long-term. I didn’t want to be like a primatologist spending years on end studying one species. I wanted to do more than that, and I wanted something that could be done in the lab and over shorter time periods – weeks or months, instead of years. So I went and did this postdoc. on Drosophila in the UK, then did a project on mice, before I finally got a job here at Maryland. Then I actually started a new bat project, but instead of vampire bats I started working on some North American bats. At that time, I think I also felt that I had got, kind of, the most interesting story out of the vampire bat, given the technology at that time, and doing anything more would have been very hard. The next step required a captive colony, for which I didn’t have the resources then. So I, instead, worked on various other bat species, on which interesting work could still be done in the field. Then Gerry approached me. He had done some bat work – in fact on vampire bats - as an undergrad at Cornell. Then he did a master’s with working on one of the bird-feeding vampire bats. He contacted me about coming to do essentially a follow up of my PhD work. He really had a very clear idea of what he wanted to do. He had read my papers very thoroughly, knew exactly what I’d found and was aware of the debate over the merits. He loved the story and really wanted to confirm the story. Although, interestingly, when he first attempted to do studies in Trinidad - catch bats, bring them into captivity, and try to get them to feed each other, the bats just wouldn’t feed each other. He actually sent me emails and asked whether I had ever seen them feeding each other! He was seeing them licking at each other’s faces, but they weren’t doing anything he could interpret as feeding. I told him - it is pretty obvious when you see it and maybe your bats are just not used to each other. Sure enough when he saw them in a place where the bats had been together in captivity for a long time he saw them feeding each other a lot - just like what I saw -

    But he did see some things that, either I didn’t see, or the bats don’t do in the wild. His bats seemed to actively compete to feed the bat that had been starved, while my starved bats would beg from other bats.  My interpretation is that it’s probably because his bats are kept in captivity and they are fed all they need all the time, whereas the bats in the wild, most of the time, don’t have a lot to spare. So it makes sense to me that they would be more picky about who they would share with.


    HS: Was handling the bats difficult?

    GW: Vampire bats are interesting in that they become accustomed to handling pretty readily. The bats that I kept were very used to being handled and didn’t struggle. In fact, even the bats in the wild, because I caught them repeatedly, often would not struggle. The first time you catch a vampire bat though, it will attempt to bite you and try to get away. And because they can run, they are a little trickier to catch than most other bats. Other bats, you pin their wings back, you have them under control.  They can’t do much. But vampire bats, because they can push with their feet, will just squirm out of your hand. But you just get used to it. And I had no difficulty handling and I don’t think Gerald had any difficult either.


    HS: How did you catch them? Could you just reach out and catch them when they are roosting, or did you have to use nests?

    GW: I learned that if you reach up and catch them while they’re roosting you will cause them to abandon the roost. The only time I would do that is when the adults had left the roost and the young were left behind. During the first several weeks after birth the pups can’t fly, so I would go in the roost, catch the young bats, band them and put them back. That also allowed me to figure out who the moms were because I could see who they would nurse. But adults I would net. Vampire bats are very smart and will learn very quickly where you put the net. So you have to constantly be creative in how you catch them. It was always a struggle, trying to be one step ahead of them.


    HS:  Where did you do the experiments?

    GW: I did this work at a cattle ranch, which had a little sort of tourist area - – and small houses. Some of houses were duplexes and some were standalone. I was in a duplex that had two bedrooms, a bathroom, and a dining room with kitchen. I converted one of the bedrooms into an observation room where I kept the bats in a cage I made with a glass front so I could observe the bats. It had openings so that I could take out individual bats and replace them, and I could weigh them before and after I feed them. It also had feeding tubes which allowed me to feed each bat separately. That allowed me to know how much blood each bat took.


    HS: You said that Nature initially rejected and asked you to resubmit. Was the final published version very different from the first draft submitted? Do you remember the big changes that Nature wanted?

    GW:  That’s a good question. I’d have to go back and check to be sure but I think that the figure with the weight loss - the one with the exponential decay curve - might have been a single panel in the original draft. I think, based on the comments, I broke it out into two - one with the data and one with the expectation. I suspect I still have the original version of this paper in hard copy somewhere.


    HS:  What kind of an impact do you think this paper has had on your career?

    GW: It’s pretty enormous, there is no question.  I’m trying to think of the timing – when I applied for the postdoc. in Sussex, either the paper was already published or I had submitted it. I’m not sure.  But I knew the results. And once the paper came out, the fact that it was in Nature, and that I was the only author, made a lot of difference.


    HS: That is quite rare isn’t it, a single-author paper in Nature?

    GW: I guess. I don’t know what the numbers are, but it will be interesting to find out. Maybe it is more uncommon now than it was then. But in terms of citations, even now, this paper gets cited more, every year, than any paper I write. 33 years after I wrote it!  I find it incredible that people still refer to it so much. But if you look at the papers that cite it, you realise that a lot of people cite it without having read it, because it’s not directly relevant. For example, they are talking about reciprocity in a different context and they just want to cite an animal example. This paper has kind of become the go-to example for reciprocity in animals.


    HS: Is that what it is cited for mostly these days – a non-human example for reciprocity?

    GW:  That would be my guess. I got to know a lot of people studying reciprocity because of that paper. In 1986, there was a meeting in UCLA, to commemorate 15 years after Trivers’s paper. Trivers was invited, Frans de Waal was invited and a bunch of other people. By that time there were a variety of studies on other taxa where people had claimed reciprocity.  We all came and we gave our stories. There was also an. But now, a lot of the examples presented at that meeting have kind of fallen by the wayside, although I think the primate literature has expanded enormously. Today, in the non-primate literature it’s harder to find convincing examples.


     HS: Did this paper have a role in you getting the current position you hold?

    GW: Oh yes. I am sure it did not go unnoticed when I was hired and then I was promoted with tenure a year earlier than I need to have been. It is all kind of connected is - having done that study and talking about that work at different places - at Oxford, at meetings in Scotland and Australia. People in the bat community got to know of me. Ted Fleming, for example, who I got to know while I was doing this work, was, I think, one of the people who wrote letters for my promotion. Also because it was published in Nature, it just got more attention. I was lucky. The timing was perfect in some ways.


    HS: You spoke about the coverage this got in the popular press, including . At the time this was published, was the idea of reciprocal altruism known and being discussed by people outside academia?

    GW:  Well, the prisoner’s dilemma is, as you know, something that crosses disciplines. People in biology, political science and economics are familiar with it. Whether it went beyond that into the non-academic community, I am not sure. But as an example, I was once asked to respond to questions, on this work, posed by grammar school kids in Japan. A woman I know, who studies bats in japan, translated, I think the Scientific American article, into Japanese. These school kids read that article and the school teacher wrote to me asking if I would answer some questions.  It was great to speak to those kids. It is not usual to be able to reach that level of audience. It is partly also the mystique around the vampire bat.


    HS: In the 32 years since it was published, have you ever gone back to reading this paper?

    GW: You know, if we had done this interview 10 years ago, my answer to this question would have been ‘no’. But recently I have had to read it because of Gerald Carter. Because of his work and the need to put his work in the context of my earlier work, I’ve had to look at this multiple times. In fact I have even pulled out all my old field notebooks with all the data and run network analyses on my associations to see what they look like.


    HS: When you read the paper now, what about it strikes you the most? Has your writing style changed substantially since then?

    GW: Well I probably never spent as much time writing a paper as I did with this. It took a lot of time and effort and a lot of rewriting. When I read it now it seems pretty dense. Every sentence has information in it. Nowadays, for a paper like this there would be a 100 page supplement that would have all the data and all kinds of other analyses. So that’s one difference. I think the writing style also seems somewhat different although it is hard for me to pinpoint exactly where the difference lies. It’s very natural history-focussed at the beginning, but there are three clear predictions after that, followed by the evidence in support of them. Even if I wrote it now, that would still be the way I would want to do it. You know, come up with such and such predictions and then come up with the evidence to support them. But what strikes me when I read this paper now is just how little data there really is! And how much effort went in to getting those data. It was Herculean.


    HS: If you were to repeat the study today, would you do it differently, especially given the availability of new technology and the theoretical advances in your field?

    GW: Even then I had many other ideas that didn’t all work. I made radio-transmitters with little waistbands that were designed so that when the waistband stretched the pulse rate of the radio would change. Using this I hoped to get remote data on how much the bat had fed. I made the device, put it on the bat and it worked. But, I also had to make holes in the membranes of the bat’s wing to get the waistband on and it would still slide off the bat’s belly when it fed. I eventually decided it was too intrusive.

    The main advantage today would be better video technology, but doing what I did would still be hard – you still need to get into the hollow, and keep the bats in view, which often requires squirming around inside the roost. So, I think what Gerald Carter did – work with a good captive population – is the way forward. He is a postdoc down at Smithsonian in Panama now, where he has created his own captive group. That is definitely the way to do it because you can observe them without any interference and manipulate them in any number of ways. It’s just that once you bring them into captivity you need to keep in mind that feeding them may influence them in more ways than you expect.


    HS: And of course, it is also easier to measure relatedness today.

    GW: Oh yes. He was able to genotype 30 microsatellite loci while I did only seven allozyme markers, which was actually pretty good. The other thing he was able to do is to record and do playbacks of ultrasonic calls. That technology was not available to me. To record ultrasound you needed a high speed tape recorder, which was a great big bulky thing with big batteries and very expensive. I didn’t have one of those. Today, doing the same is still not cheap, but much cheaper than earlier. And less cumbersome.


    HS: You said that you went back to your field site 15 years ago. Were the colonies you studied still there?

    GW: Yes, there were still bats in the place I worked at, the last time I was there. In a lot of places in Latin America, vampire bats are actively managed or exterminated because they are carriers of diseases of livestock – Rabies and Equine Encephalitis. But in the nature preserves they don’t harm the bats, so they are still reasonably common. Especially if there are livestock in the landscape, they have abundant food and it’s easy for them to survive and do well.

    In the specific site I worked at, the bats were there 15 years ago. I tried but I didn’t find any of my banded bats. Some of the trees where I had watched bats had fallen over and no longer had bats, but there were still a couple that did. Vampire bats can easily switch roosts. They are not tied to a place and move around quite often.


    HS: Had your field site changed a lot since when you worked there?

    GW: Yes. It was no longer an active cattle ranch, though it still had some livestock. I know that it was turned into an ecotourism kind of place and is still called ‘Hacienda La Pacifica'. It is near the town of Cañas in Guanacaste province. The people who owned the cattle ranch were from Switzerland, originally, and they managed the land better for wildlife than most cattle ranchers. They left large tracts of second growth forest and pretty good strips of riparian vegetation along the rivers that bordered their property. It was in this riparian forest primarily where all the hollow trees were.


    HS:  What would you tell a student who is about to read this paper today?

    GW: Well, I think I would encourage him or her to read the more recent papers of my graduate student, as a way to bridge the gap between the 1984 paper and now.  I was pleasantly surprised that what Gerald found, with a lot more data, was not all that different from what I had said in the 1984 paper. In the '84 paper, the point I tried to emphasize, which is often not mentioned, is that kinship and association are equally important. Most people focus on the reciprocation, maybe because that’s the more unusual result. Interestingly, in the recent work kinship seems to be less important. Now that may just reflect the composition of the bats in the group. The bats Gerald used came from more than one place, and so many were not closely related. Whereas in my site, bats were probably a lot more closely related. At this point it is an open question - if one were to go to other places and look at vampire bats and survey relatedness what would one see? It might be that what we found was somewhat unusual or maybe it was typical. But one thing that is true is that they don’t need to be related to feed each other. I think that’s pretty clear. I also think that the bats are highly dependent on food-sharing. If they didn’t share food, they couldn’t live for 18 years as some of them do.


    HS: Is this your favourite paper?

    GW: That’s an interesting question. I guess it is in many ways. If I went through my papers I could tell you why I liked each one of them, but this one is easy to like from many angles. The funny thing is my dissertation had three main papers in it – this one and two, published back to back in Behavioural Ecology and Sociobiology, on social organisation of the vampire bat – and . The latter two are the papers that I had always imagined I would write. The data that I collected was kind of geared towards producing those papers. This paper was an afterthought. I did the experiments and once I realised how the results had turned out I thought – Oh my goodness, I need to flesh this out quickly. So, the time period in which this paper was conceived and finished was much shorter. And, of course, it had much greater impact too.




  • Post date: 1 year 10 months ago
    Citation for this post: BibTeX | RIS

    In 2000, Mandyam Srinivasan, Shaowu Zhang, Monika Altwein and Jürgen Tautz published a paper in Science showing that bees estimated distance travelled during flights by “the extent to which the image of the world has moved on the eye”. In January 2016, I revisited this paper with Mandyam Srinivasan, to discuss its impact and relevance in the context of current research on the topic.

    Date of interview: 17th January 2016


    Hari Sridhar: Have you ever read the paper completely after it was published?

    Mandyam Srinivasan: I suppose I haven’t read the paper completely since the time it was published, but there were several sorts of things that it lead to - experiments one could do based on what we found in this paper. And so we have continued work along those lines.  

    One of the things that this study suggested was that you could scale down large-range flights, which happen outdoors in natural environments, to the lab. You can simulate a long flight using a short tunnel. With this, you can do interesting things, like study how bees do what is known as path integration - when a bee goes along a tortuous route, where it makes turns left and right. That’s hard to setup in an outdoor environment. You cannot force bees to take a particular route outdoors,  but indoors you can set that up - make bees go along a particular trajectory and then see how they integrate the distances they have travelled, till they come up with a final vector that shows the distance and the direction to the food source. So these kinds of things we started to do after this paper.


    HS: Apart from the research it lead to in your own lab, can you give us a sense of research on this topic before and after this paper, to get some idea of what kind of impact this paper has had.

    MS: I guess people have, since then, done similar kinds of experiments with other species of insects. They have worked with stingless bees, and I think also with wasps - though I am not totally sure of that. But certainly with stingless bees, where they have demonstrated similar behaviour. And probably a little more significant is the fact that a number of robotics groups have started to use this to enable aircraft systems to measure distance flown. In the absence of GPS and things like that, can we use vision to do our odometry? That question has been there for a while - I wouldn’t say we are the first ones to suggest that approach - but certainly the fact that animals do it has encouraged a lot more people to use that approach, ourselves included. . And it’s turning out to be quite useful.


    HS: At the time when you published the paper, did you have some expectation of the kind of impact it might have? How does what has happened compare to that expectation?

    MS: I really don’t know, Hari. It’s hard for me to tell.  I have to go back and look at the citations. But people are starting to use the tunnel. We were probably the first ones to fly bees in tunnels, and since then a large number of people have started to fly bees and other insects in tunnels. That’s probably one of the main impacts – the general idea of scaling down these experiments in the lab, making them fly in the tunnel and looking at all these behaviours that they do - controlling their flight speed, negotiating narrow gaps, measuring distance travelled and so on. That’s probably largely due to the work that came out from our lab, I would say. But there are some interesting puzzles in it that still bother me and which still haven’t been solved, so maybe we could talk a little about that.


    HS: Sure.

    MVS: So one of the things we said was – okay, a bee flies a certain distance to a food source, it comes back and reports to its nest mates, through the dance, how far it thinks it has travelled, based on the optic flow it experienced. The optic flow varies depending on whether the environment was tight and close, or more open, with objects further away, right? But that does not matter because another bee that observes the dance and flies to find the food source will take the same route - it will experience the same environment – with the same optic flow. In other words, it doesn’t matter if your yardstick isn’t correct as long as everyone is using the same yardstick, right? That’s one thing.  But there is another potential problem – if the bees are using the ground to measure optic flow, then the height they are flying above the ground matters - when you are flying very low, optic flow is high, and when you are flying high, it is low.  Either everybody is flying at the same height above the ground, or they have to have some mechanism for knowing how high they are. This is still a mystery – we don’t know how they do it. If you fly in a very dense forest, then there is a lot of optic flow coming from the sides, because you are passing lots of tree trunks and things like that. The ground may not be very important then. But if you are flying in an open meadow, then all you have is the ground right? That is your only source of optic flow. Then you have to somehow regulate the height, or know it and account for it.  How they do that is still not known.


    HS: When you read this paper now, what strikes you about it?

    MVS: It is interesting. Usually, I get very worried when I read my own papers. I feel - why did I study this, or it doesn’t make sense, or I could have expressed it better. But this one, strangely, doesn’t seem like that. At least, I cannot find anything I am particularly embarrassed about! One thing of course is that once the work has been done and published, everything seems quite obvious, right? Some of these calculations I have done here, they almost seem a little superfluous. Someone could look at this and say they could surely work that out for themselves; that it is a bit redundant. But there are also some things I feel, maybe, we could have elaborated upon, if there was more space.  For example, explaining we are not the first one to investigate the nature of the honeybee odometer. Karl von Frisch, the Nobel laureate, had already looked into that, .  He did outdoor experiments, where he had bees flying from a hive to a feeder he had placed a long distance away – 500 metres away - and then measured the dance. It turned out that the bees were indicating the correct distance. Then he put small weights on these bees, made them fly the same distance again and found they signalled a much longer distance. From this he concluded that the bees must be estimating distance based on energy consumed.  But we think what was happening there was that the bees with weights were flying closer to the ground and therefore experiencing much greater optic flow. This has not really been tested yet, so that’s something that someone should probably try and do. It would be interesting to see what they find. Again, these things are hard to do in the field, you know, because it is hard to measure the flight of bees outdoors.


    HS: Is this something you wanted to talk about in the paper but didn’t?

    MVS: Yes, I would have liked to talk about this, but space was a limiting factor.


    HS: What else do you recall about your experiments, when you read this paper now?

    MVS: I was so sure these experiments would not work, because we had never worked with bee dances before. We had done a lot of other experiments with bees - . All of that we had done in the past. But we had never actually looked at the dance. So it’s really, I suppose, beginner’s luck. One of our collaborators in Germany, and the senior author on the paper - Jürgen Tautz - sent to us a student - Monika Altwein - who, I think, was a senior undergraduate at that time, to do a little project in our lab. Part of her project, actually, was to show us how to film and analyse the bee dance. That was how we ended up studying dance behaviour for the first time. So it was really nice that we could get a paper published in a journal as big as Science! Very fortunate. In fact, I was not at all sure if we could fool the bees in such a comprehensive manner, just by putting them inside a slightly unusual environment.  That’s why I was convinced that the experiment would not work. The first few times we did the experiments, we couldn’t believe that it actually worked. But I think that ours is certainly not the full explanation; I don’t think it is the full story. I find it hard to believe that if a bee flies, for example, distances greater than 10 kilometres in search of food, it relies purely on optic flow.  It must feel tired, it must feel exhausted, its crop would be almost empty, and it would feel a sense of fatigue - all these would also indicate distance in some way, I think. Maybe for short to medium flights, optic flow is the only cue, but for longer flights I think other cues will be required.


    HS: Do you continue to work with your co-authors on this paper?

    MVS: No, not anymore actually. We sort of drifted apart. was a colleague of mine - in fact, I sort of appointed him to our department - and we have done a lot of lovely work together. I owe him a lot really, for all the stuff that came out during that period. We were working together in Canberra for a long time, at ANU, but when I moved to Brisbane, he stayed behind in Canberra and continued his work. He has retired now, but he still continues to work, to collaborate with a lot of universities in China. And he continued the collaboration with Jürgen Tautz too, for a while, but I’m not sure what has happened recently. I’m not sure what Monika is doing now. I’m not even sure if she did a PhD.  I keep in touch with Jürgen Tautz once in a while, exchanging New Year greetings and things like that, but I don’t work with him anymore.


    HS: What about the experimental setup and the colonies - do you know what’s happened to them?

    MVS: The colonies we used would have died by now and there will be new generations. But that facility, I think, was still being used, until recently, by a colleague of mine, a guy who is a molecular neurobiologist. His name is , and he was interested in learning and memory in bees, and looking at the molecular basis of learning. He was using those colonies for a while. I don’t know what’s happened now.


    HS: This facility was in the university campus?

    MVS: Yes, there were a couple of different areas. One was an all-weather bee flight facility - a greenhouse which was converted to a flight facility. The idea was that we could do experiments with bee flight indoors, independent of the weather outside. We had hives which were located inside the greenhouse against the wall, with a small opening to let the bees go outside and get their food and everything, and also an opening on the inside, which we opened from time to time to let the bees into our arena for training and experiments. When I moved to Brisbane, they built another facility like that for us, in the rooftop of one of the buildings. We also had another sort of a small field station, where we could do outdoor experiments with bees. Both these facilities were used by others, after I left, till recently. Sadly, I think that insect vision programme over there is drawing to a close, because all the people there are getting old and close to retirement. Just like me!


    HS: Do you think your writing style has changed from the time you wrote this paper?

    MVS: Yes, I think it has gotten worse now! When I read this paper now, I am quite happy with the way the writing sounds.


    HS: Did you do most of the writing for this paper?

    MVS: Yes. As it turns out, in most cases, even if I’m not the senior author, I end up doing quite a lot of the writing because, quite often, students are relatively inexperienced. I try to encourage them a lot, of course, to write their own things, but sometimes there comes a point when, if you are trying to submit it to a journal, you have to make sure the language is reasonable. So I did have a fairly strong hand in the writing of this paper.


    HS: It is very nicely written and easy to understand even for an outsider like me.

    MVS: Yes, at least in the old days, it was important, if you were trying to publish in Nature or Science, to be as lucid as possible. Things have changed now. If you read the average Nature or Science paper nowadays, it’s so highly specialised, so technical, it’s very hard to follow. And there is a lot more material too; you are expected to put a lot more into it. A small idea, a small result, is no longer something that Nature or Science will even think about, unless it’s something really profound.  And most often, nowadays, you need to have a strong molecular biology component, otherwise journals don’t even look at it. I think, if I submitted something like this now, it probably won’t get accepted.


    HS: Did this paper have an electronic supplement?

    MVS: No. As far as I can recall, everything went into the main paper. I think the whole concept of supplementary material came a little bit later. And now of course, 90% is in the supplementary material. The actual paper is like the tip of the iceberg.


    HS: Do you remember if your paper changed a lot from the first draft?

    MVS: I don’t think so. Actually, we were surprised it went through very smoothly. I think we got it back with fairly minor corrections, you know. In fact, I got the good news when I was in Bangalore on a visit; so that was nice.


    HS: Given the theoretical and technological advancements in your field, if you were to redo these experiments today, would you change anything?

    MVS:  Okay, when filming the dance behaviour of bees on the hives, you have to be careful not to shine any directional light on them, because that can distract their dancing.  In fact, they assume that light to be the sun, get disoriented and confused, and start to use that as a bearing. Of course, without light we can’t do any filming, so we tried our best to provide a diffuse source of illumination. We did some controls and there didn’t seem to be any steady bias, so we went ahead and used it. But if I were to do the experiments again today, I would probably use infrared illumination, which the bees don’t see. The cleanest way to do this experiment is to have a totally dark room, shine infra-red light on the dancing bees - which the bees cannot see - and then use an infrared sensitive camera to film it.

    The other thing I would change is the analysis of the dance behaviour. For this paper, we digitised and analysed the dance manually, step-by-step. It was very tedious and painstaking work, trying to track the position of these bees over a huge number of video frames. But since then, an engineering student from the University of Maryland US, who came to do a little stint with us for a few months, has developed a nice algorithm for automatically tracking bees while they were dancing. With these automated bee trackers it is a lot easier to analyse the dances and get a lot more data. So certainly that would have been a very useful thing.


    HS: And in terms of experimental design – would you change anything if you were to repeat the experiments today?

    MVS: No, I can’t think of any way to improve upon it.


    HS: What would you say are the main takeaways from the study?

    MVS: To my mind, it proves, fairly conclusively, that it is optic flow that bees are using to measure distance travelled. That really is the main thing. And it also calibrates that, in terms of units of optic flow per waggle dance duration. It’s a new way of calibrating the odometer, because previously it was all in terms of distance travelled. But now, we are saying the fundamental unit the bee is measuring is not the distance, but the amount of optic flow. For me, looking back on it and seeing what Von Frisch did - he did those very nice, clever weighting experiments, but, as I described earlier, it seems like he might have been misled. It worries me that, by the same token, we could have missed something very important, which someone else later might come and point out.


    HS: But it hasn’t happened so far?

    MVS: No, It hasn’t happened.


    HS: And you haven’t discovered anything problematic, yourself?

    MVS: I haven’t thought of anything. I mean, like I said, there is still a lot which is unexplained here, but I haven’t seen anything that contradicts, or finds a completely different explanation for, our results. Except for very long distance flights. I don’t know if anyone has really found other cues that bees could be using when they fly large distances.


    HS: And is the calibration for waggle duration in terms of optic flow units - “17.7 degrees of image motion per millisecond of waggle” - still undisputed?

    MVS: I would say so, but I am not sure. I have to go back and check. That’s a good point. Certainly, give the same numbers, and I know people . But I will have to go back and take a look to say for sure. That’s a good point.


    HS: What kind of impact has this paper had on your career?

    MVS: Well, I was being considered for election to the Royal Society around the time this paper got published. So maybe it made a difference to my election as a fellow. Also, I had applied for what’s called a Federation fellowship, one of those nice senior professorial fellowships, which are highly competitive in Australia. And that came through as well. So I do think it helped my career quite a bit. And to think that the work itself was almost completely accidental, a result of just sitting and musing and saying - what would happen, you know, if something like this happened etc. It certainly didn’t come from a grant we wrote up; it was just something on the side.


    HS: Does this paper come up in conversations even now?

    MVS: Quite often.  At least people in the field seem to remember it and know it quite well. Although, I must say, I don’t know how much of an impact it has really had on the science.


    HS: You don’t keep track of where it’s being cited?

    MVS: No, I haven’t really looked at the papers that have cited it. I mean, I suppose I could go into Google and check that.


    HS: As of today, it’s been cited 280 times

    MVS: Okay, so it’s not a very high impact paper. It’s been around for a while. I haven’t looked at the papers in detail to see in what context they have cited. Maybe I should do that sometime. Maybe when I retire!


    HS: Is that because the papers that cite this are somewhat outside your main research interests today?

    MVS: Maybe. I have seen a few engineering papers cite it, just to say - hey look, animals do this too you know. They will say they are going to get their robots to use visual odometry to measure distances travelled or something and by the way, animals do it too. Just to add strength to the paper. That sort of thing.


    HS:  In concluding your paper you say “In the future it should be possible to study mechanisms of navigation and path integration conveniently, and under controlled conditions, by training bees to fly through short tunnels arranged in various configurations”. Has this happened?

    MVS: Yes, , to see what happens when bees fly a stretch horizontally and then fly vertically upwards, to get to a food source. The interesting question there was whether they will measure the optic flow rate independently of the direction in which the image is moving in the eye? Because when they are flying horizontally, the image is moving from front to back in the eye, but when they go up the tunnel - bees fly up like helicopters - the image flow is vertically downwards. We wanted to know whether they would integrate horizontal and vertical distances in the same way, and it turns out that they do.  What is even more interesting is that they don’t sum these two distances vectorially, but instead provide the total scalar distance travelled, i.e. the perimeter distance. Very interesting; I don’t know why they do that. Even in the , where we simulated forward flight and then flight in a perpendicular direction, the bees gave the direction as the vector of the sum of those two vectors, but the length was the total. Why they do this is still an unsolved enigmatic puzzle. Some people say -  okay, if a bee is forced to take a detour around a hill or something, to go to a particular food source, then the physical distance that the bee needs to travel is not the vector but the perimeter distance, right?  So if the bee comes back and gives this full distance that needs to be travelled, that is useful information for the other bees, which are contemplating whether or not they should go to that particular food site. If the bees are comparing two different potential food sources to decide which one to go to, it might help to get an idea of the true distance and not the short cut distance. That’s the best explanation so far, but it is still a bit of a puzzle.


    HS: Last question - in general, do you ever find yourself going back to the papers you have published?

    MVS: If I am working on something that’s based on what we have done in the past I would certainly go back to check exactly what we have said and so on. The other time I do it is when someone emails me with a question about it. That happens quite often- usually, people asking about methods. So then I go back and read the paper. Also, when writing reviews, I often have to go back and read my earlier papers.






  • Post date: 1 year 10 months ago
    Citation for this post: BibTeX | RIS

    The INNGE working group felt that developing core ecological teaching in schools was an important topic to address. Ecology is often not considered as a core subject in curricula, but is rather considered as a side subject, especially at primary, secondary and high school levels. We believe that this should be changed to help bring ecology at the center of many issues at local, national and global scales. But how?

    We invited four speakers to discuss this topic in the on May 12.

    Karen Devine and Samina Zaman () focused on ecology in the UK, and how the (BES) has developed its education work and how they have engaged with education policy and the national curriculum. Samina also talked about the national that was launched in 2014 for training PhD students on science communication to connect with schools. ==> (~20 min)

    Chris Midden (Middle school teacher, Illinois, USA) explained his teaching of earth science and ecology to 11-12-year-old students in the US. He uses the to contribute, with the students, to data collection and to approach ‘real research’. He uses the ‘problem-based learning method’, and he highlighted the importance to become more aware of one’s (local) environment before asking questions and conducting research. ==> (~9min)

    (James Cook University, AUS and executive editor of the Journal of Environmental Education) talked about the evolution of the ecological curriculum in Australia. States and schools are quite autonomous with regards to how ecology is addressed in schools, and there is a demand from Australians to have a more national ecological interest. Hilary also highlighted the existence of the and teacher education resources that offer a wide range of resources for ecological education on marine ecology. ==> (~15min)

    We ended the forum with a discussion based on the questions from online participants ==> (~39min)

    Here is the full video (~1h22min):

    from on .


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