Nature Podcast

This is a transcript of the 4th September edition of the weekly Nature Podcast. Audio files for the current show and archive episodes can be accessed from the Nature Podcast index page (http://www.nature.com/nature/podcast), which also contains details on how to subscribe to the Nature Podcast for FREE, and has troubleshooting top-tips. Send us your feedback to podcast@nature.com.

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Adam Rutherford: This week, geography and genetics in Europe:

John Novembre: What we see is a striking map of Europe where the individuals are arranged by their genetic variation according to their geographic location.

Kerri Smith: We are going to need a bigger computer and possibly a fan:

Cory Doctorow: The top floor of the Ice Cube is a giant cooling apparatus as you get with theses big data centres and then the floor below it is a giant empty floor for the next big cooling apparatus.

Kerri Smith: The problems of big data at the Sanger Centre, just how do you begin to manage petabytes of information.

Adam Rutherford: And in the run up to the US elections, is climate policy top of the agenda?

Steve Cochran: I was talking about this the other day and described climate policy as the younger brother that your mother makes you take to the movie when you're about to go with your friends when you're a teenager and have a good time and you're really not happy about it and if you can drop him off somewhere along the way, you will.

Adam Rutherford: Hear from the first part of our US election special series. This is the Nature Podcast, I'm Adam Rutherford.

Kerri Smith: And I'm Kerri Smith.

Kerri Smith: Your genes can reveal a lot about you, but did you know that they can pinpoint where you live to within a few 100 kilometres. That's among the results of an analysis of several thousand genomes collected from different European populations. The data was collected by pharma company GlaxoSmithKline and crunched by an international team of scientists. I spoke to first author John Novembre of UCLA about the results. But first his colleague Carlos Bustamante told me how the study began. Nature advance online publication (31 August 2008)

Carlos D. Bustamante: This was a study that began with a collaboration about two years ago with GlaxoSmithKline and what GSK had done was go out on genotypes that is score about 500,000 variable nucleotides in the human genomes in close to 6000 people and the reason they had done this is that they were interested in getting a broad sense of a human genetic diversity with an eye towards the design of genome-wide association studies and it turned out that the data was heavily composed of individuals of European descent, so they had close to 3000 individuals of European descent and it's one of the first analysis that John did and when he did that he sort of came back to us and said, look at this, this is amazing. This is a map of Europe.

Kerri Smith: John Novembre who crunched the data told me more about how the team went about their work.

John Novembre: What you end up with this data for each individually have observations at very large number of single nucleotide polymorphisms. These are locations in the genome where there has been a mutation in human history and so there are two variants that typically that exist in human populations and the data is very rich. For each individuals you have 500,000 observations and what we wanted to do was to summarize the patterns of variation so that we could understand more easily what's going on in these genomes and when we do that and summarize the data in just 2 dimensions, what we see is the striking map of Europe, where the individuals are arranged by their genetic variation according to their geographic location.

Kerri Smith: Quite a striking result, was he surprised by what they found?

John Novembre: We had some sense that there would be population structure within Europe that there would be some ability to discern individuals from different regions of Europe and we might have expected it to exist on larger spatial scale, but what we saw is that you can actually do it on a quite a fine spatial scale, so that you see even within Switzerland, if you break up Swiss individuals by whether they are French-speaking, German-speaking, or Italian-speaking, you can see patterns of differentiation.

Kerri Smith: There were a few different applications for dataset like this. Medical genetics as well interested GlaxoSmithKline, John told me.

John Novembre: The reason that GlaxoSmithKline is interested in it was because they wanted to form a database of individuals that they could both use to study to do genome-wide association studies for understanding genetic variants underlying adverse drug responses and a database like this of individuals allows them to get very well matched controls for any cases of adverse drug response of the patients that they have. The second application that they are interested in is that it also gives them a database for when they do find an association of a particular gene with a, say, adverse drug response they can immediately look at its frequency across many different populations.

Kerri Smith: Plenty of scope for applying these methods to so called pharmacogenetics then, tailoring drugs to different genetic backgrounds, but what about all your amateur genealogists. It's more of a leisure time use that GSK had in mind for the data, but are there implications for those of us interested in uncovering our family trees. Carlos Bustamante again.

Carlos Bustamante: Oh! We think so. We think that's probably to us one of the most exciting aspects of it, because there is so much interest in the sort of personalized genetics or personalized ancestry. The paper focused on individuals where we could see that they had four grandparents from the same geographic region, but our hope is to be able to develop novel algorithms that could then go through and take individuals of admixed ancestry within Europe and go through and say, Oh! this chunk looks like it came from Spain, this chunk looks like it came from Italy, this chunk looks like it came from Eastern Europe. It goes to show that if you have fine enough sampling and deep enough sampling and if you could then overlay regions within countries, you might even be able to take this further and say this is particularly southern Italian haplotype or region of the genome versus Northern Italian

Kerri Smith: It might even help Carlos with a more personal quest of discovery.

Carlos Bustamante: So, there are other populations in the GSK dataset and we've got some global analysis that we've been undertaking. There are some genomes from the New World which to me would be really, really fascinating. My family is from Venezuela and from Spain and I've always been really fascinated by the colonization of the New World and trying to peel apart and understand how that happened and whether we could go through and try to understand admixture in Hispanic/Latinos, it's one of the areas I am particularly interested and I think that will be really fine and very exciting area of research, particularly as it relates to the issue of personalized genomics.

Kerri Smith: Carlos Bustamante there of Cornell University and before him John Novembre of UCLA. Coming up later in the show we will be peering into the Black Hole at the centre of our galaxy and discovering moths with a repertoire of repulsion techniques.

Adam Rutherford: But first, Happy Birthday Google!!! 10 years old this week. Google the internet and computers have revolutionized how science is done. But it is only very recently the computational power has enabled the generation of un-precendented amounts of data. Just like in the previous report we're talking about giant projects like large scale genome sequencing and also the Large Hadron Collider at CERN which is due to go online next week. As part of a special issue of Nature this week on big data, that science that generates and requires colossal volumes of bytes, science fiction writer and Boing Boing blogger Cory Doctorow visited the LHC data storage facility as well as the genome sequencing Sanger Centre to find out exactly where and how a petabyte of information is managed. Cory joined us in the studio earlier this week. Okay Cory, my first computer an Acorn Electron since you asked had 32K memory of just enough to play Pac-Man. You went to the Sanger Centre and you went to CERN to get a feel for really what big data storage actually feels like. Tell us about the Ice Cube.

Cory Doctorow: So, the Ice Cube is the Sanger's Data Centre and they practice something called IT crop rotation. So what they do is they have a huge data centre and they reserved a quarter of it from use and the idea is that when the computer that does not yet exist comes into existence with its own power consumption specifications, it's own cooling needs, and cooling and power are the two big factors you play off on each other because you know, as Bruce Sterling says you dig coal with your space bar, right, every time you calculate something a little bit of heat is released into the universe and then you need to spend some energy turning that heat back into cool to keep all the precious components from melting down. So when it comes time to build that new data centre, they're going to stick it in that room and they're going to decommission a quarter of the old data centre and then they'll build the next data centre and the new decommission section and so on, tearing it out and putting it back in again. Now the top floor of the Ice Cube is a giant cooling apparatus as you get with these big data centres and then the floor below it is a giant empty floor for the next big cooling apparatus and it's sheathed in this blue glass that has no functional characteristic but makes it look cool.

Adam Rutherford: Okay. So, for the Sanger Centre there generating genome sequences relatively straightforward data, although lots of it, what is the meat of what the LHC is going to come out with?

Cory Doctorow: I went to the Large Hadron Collider as well at CERN in Geneva and you know they got pretty comparable data needs, but they got really different data characteristic, so both of these devices, or both of these centres, really take an enormous amount of data off an instrument, in the case of the genome it's the sequencers, in the case of the Collider it's the Collider and that data comes in the form of huge uncompressed output from CCD's, charge-coupled devices, which are kind of what you get in your digital camera. In the case of the genome, they take lots and lots of pictures of very, very small sequences of DNA and then they kind of average them out and get a report from the instrument and the conclusion that the Sanger has is that those tiffs, those uncompressed images, they can just toss them out again. So that's a lot of data, which just gets thrown away as soon as it has been processed, they can keep it for a couple of weeks and then throw it away, which keeps their data very manageable. By contrast, the physicists, they tune their instrument based on their conclusion, so they describe it as like imagine a wall of bricks and each of those bricks is a sensor and a particle hits the brick and if it hits the dead centre they get a really good characterization of what that particle is, but if it is off centre, some of the energy is absorbed by one brick and some is absorbed by some of the neighbouring bricks and some of it falls in the cracks in between and they try to characterize that information and every time they get a direct hit they learn more about these indirect hits, so about once a year, they plan on reprocessing all the information that goes into their data centre and this means, that they have to keep a lot more information, not online, but near line, ready to be loaded back into the computers, processed, and then spat back onto these tapes again. They're these enormous tape robots in the basement. You know, I had been in IT a long time. I was a systems administrator I have never seen a bit of kid at school as these giant tape robots.

Adam Rutherford: But isn't one of the limiting factors going to be number of the people available, isn't the data going to sit there for hundreds of years, while scientists fail to get grounds to actually employ people to understand the, you know, the terabytes of information that's coming out.

Cory Doctorow: Well, this is a great question, you know, there's a kind of legendary story about a guy who was asked to spec out a computer that will solve some very computationally intensive problem and he sits down to do it and he says, you know, assuming process of growth goes the way its going now, if I want to solve this, the cheapest, fastest way to solve this is to wait 7 years, do nothing. Then buy computers and then solve it in 3 years, whereas if I bought the computers today, it would take 12 years, right. So this is total 10 year run and I brought this up with the guy who runs the IT centre, Tony Cass at the Large Hadron Collider and he said oh yeah like anyone is going to let you leave money in your budget for 7 years if you're not spending it. Right so the real politic of this stuff is that it may make more sense to process this data in 7 years, but it's wildly unlikely that scientists will be willing to sit on their hands for 7 years waiting to buy their new equipment and that the people who fund them are going to be willing to say yes, why don't you just put that grant into a long-term treasury bills for 7 years, and then take it out and buy the computers of the day.

Adam Rutherford: Cory Doctorow, co-editor of the blog Boing Boing, amongst the terabytes of output he also generates and there's much more of that interview in our first podcast extra this week, where News and Features Editor Ollie Morton, joined us to talk about amongst other things the behemoth that is Google.

Kerri Smith: The big data issue is all online naturally at http://www.nature.com/news and features articles on wikiomics, environmental data and terabytes more.Jingle

Adam Rutherford: Now it may not have escaped your attention that there's US presidential election coming up in November. This week, Nature kicks off a miniseries of four special podcast extras on the big science issues influencing the race for the White House, Kerri.

Kerri Smith: John McCain and Barack Obama have been campaigning for the hearts and minds of American voters on the economy, on Iraq, but where did they stand on the big science issues. This week sees the start of a special series of podcasts on US Science Policy and what it will look like under a new president. Nature News and Features editor Alex Witze has joined me in the studio, as has columnist and host of the discussion David Goldstein, hello both.

David Goldstein: Hello.

Alex Witze: Hello.

Kerri Smith: Alex you've masterminded these discussions and you've chosen three topics. Tell us about those.

Alex Witze: Sure. I wanted to take a look at some of the issues that are of interest to both the scientists and also may be perhaps to the general public. So we've chosen three themes. One of which is, sort of, the obvious things on the minds of lot of voters these days is energy and climate issues, also taking a look at biomedical issues and health issues turn to be a lot of more importance during the campaigns, but there's also some things to be said about things like NIH funding and where research and biomedical fields is going with the new administration and lastly we're taking a look at the topic of innovation where the US should be leading, are we falling behind internationally, are we training the right amount of scientists and engineers for the future.

Kerri Smith: David you've been hosting the three debates for us. This week was on climate and energy now what are the issues that seem to have stood out to the experts who took part in the discussion as important in both McCain and Obama's policies?

David Goldstein: Well both Obama and McCain have said that they want to have a cap-and-trade system to reduce US Greenhouse gas emission, which would be a big change from current US policy, but a lot of the discussion then was about what might actually happen to implement that. How difficult will it be? We're a long way from actually getting a system in place and so the experts talked about the nature of the policy, the kind of choices that need to be made, what will happen with research and development as part of that.

Kerri Smith: Now Alex just mentioned to us that climate change is on the minds of voters, but is not the most voter friendly issue I guess for a new president, is it?

David Goldstein: Now I think really, energy policy is on the minds of voters, and for some voters that includes climate policy. One of the things that we talked about was the fact that there has to be some pain in terms of climate policy that involves raising energy prices through one mechanism or another and that's not something that the candidates have been anxious to talk about.

Kerri Smith: And here's Steve Cochran actually with some wise words on that.

Steve Cochran: I was talking about this the other day and described climate policy as the younger brother that your mother makes you take to the movie when you are about to go with your friends when you are a teenager and have a good time and you're really not happy about it and you're irritated about it and if you can drop him off somewhere along the way you will and pick him up may be later. This is going to be hard for the congress, because.

David Goldstein: This is actually asking to take your little brother and you are him paying him for out of your own pocket.

Steve Cochran: That's right. And sorting through the interests that are potentially affected here is going to be very difficult and we've seen frankly a great deal of reluctance on the part of members to really engage in this.

Kerri Smith: Steve Cochran there of the Environmental Defense Fund based in Washington D.C. David, are there any obvious differences in the energy and climate policies of the candidates that your panel has pulled out.

David Goldstein: Well there are some specifics in terms of the way that the two candidates would run a cap-and-trade system. So Obama supports auctions, McCain has been more sceptical of that, the guidelines they have for cuts in 2050 are different, but I think the main concern is whether and how we'll go forward in the short run. That's going to be more important than the differences out at 2050.

Kerri Smith: So that was actually going to be my next question. What are the expert's main concerns about where a new administration might take these policies?

David Goldstein: I think the biggest concern is just that it won't be a high enough priority to really get it done early on and the more time we take, the harder is going to be it to have the cuts. So I think the biggest concern is that the candidates keep this as a priority that it'd not get overtaken by short-range energy concerns and that they work with the congress and the public to actually implement a program. I think that's not to be taken for granted despite willingness to both candidates to take on the issue.

Kerri Smith: Nature columnist, David Goldstein there and for the full-length discussion visit http://www.nature.com/nature/podcast or if you've signed up to the Nature pod and Itunes it's already arrived. Genius!

Adam Rutherford: Coming up in just a moment, Geoff Brumfiel zooms in on the plug hole in the middle of our galaxy. Before that Charlotte Stoddart blogs right off to a special conference in London this weekend, organized by our very own social networking sites, Nature Network. It's kind of like, facebook for geeks.

Charlotte Stoddart: Saturday's conference in London gave bloggers from Europe and beyond a rare chance to meet and discuss their art face to face. I joined them at the lavishly refurnished Royal Institution to find out who's blogging about science and why.

Vaughan Bell: My name is Dr. Vaughan Bell. I'm a psychologist, based at the Institute of Psychiatry in London. I'm mainly concerned with researching psychosis and the effects of brain injury.

Charlotte Stoddart: Vaughan writes on the neuroscience and psychology blog, Mind Hacks.

Vaughan Bell: I guess I started to blog really as an outlet for lots of the interesting things I stumble across in science, be they kind of, headline publications or be they interesting snippets of conversation or interesting little snippets that we all pick up but which may not be useful enough or interesting enough to publish in the main academic literature. So for example, I was discussing déjà vu with a colleague, when we were discussion temporal lobe epilepsy and he happened to mention déjà vu is excellently described in Iron Maiden song So I looked at the lyrics of Iron Maiden song and discovered some of it was actually written a letter to the British Journal of Psychiatry and describing exactly this and why scientifically it was such a good phenomenonlogical description of déjà vu. Now here's a really good example where that's a fascinating nuggets of information that's great for people to you know, be able to access and interest us all, but there's very few places nowadays where we get now, left for that.

Charlotte Stoddart: One of Vaughan's biggest fans is Ben Goldacre, who writes a weekly newspaper column and blog called Bad Science. While Vaughan is inspired by the nuggets he picks up in conversation with friends and colleagues, Ben is motivated by misrepresentations of science in the media. In his opening speech at Saturday's conference, he explained why blogs are in some ways better at covering science than other media.

Ben Goldacre: I think what's interesting about blogging about science is that there's structural differences between blogs and mainstream media. They actually reflect some of the, sort, of better qualities of academic science itself. So for example, if you say something really stupid or wrong on your blog, then there is an army of bastards waiting to point that out in their comments and that's sort of good sort of cautionary note, but it's also very valuable because there's nothing wrong with being wrong. And when people point out that you're wrong, you can, kind of, engage with it and discuss and then may be conclude that you're wrong. The other thing, I think is really valuable about blog services is they link to the original primary research that they are praising or they're criticizing or that they're using to bolster their argument their blog post and you can go and read the abstract. You can read the whole paper if you want.

Charlotte Stoddart: Jennie Rohn, who is a post doc at University College London and blogger on Nature Network, also thinks that blogs cover science in a way that mainstream media don't.

Jennifer Rohn: I think that if you look around images of scientists in the media and popular culture say in films, TV programs, you don't actually see that many accurate representations of science and scientists and that's sort of a problem because if you don't understand how science is done and you're a bit nervous about it, you might be more reluctant to trust the scientists when they give advice. I, sort of, thought that a blog could be a good format for revealing the scientific lifestyle to those who don't know anything about it. I thought well if you're inside the lab, the secret place that nobody knows anything about, maybe you could tell your own story in your own voice and you could interest people in the profession of science that way.

Charlotte Stoddart: So far then we've heard about a blog based on science snippet and how blogs can convey both the results of research and the daily grind of lab work, in a way that mainstream media can't or don't. But can blogs also be used to do science. Peter Murray-Rust, a professor at the University of Cambridge thinks they can. He and his research group are looking at how the web can be used to learn more about molecules.

Peter Murray-Rust: We're also finding that we can use blogs as part of our research and that's particularly true, where we're bringing together technology, so there's a number of chemical blogs which are now all using the same technology for identifying molecules, chemical reactions, and other things like that and as a result of this, we can use automatic methods, we call them robots to sound posh, which can go out and find molecular information anywhere on the internet and bring it together and see what patterns we get out of it and hopefully we'll come to a stage where robots can even give us some ideas which might end up as new scientific hypothesis.

Charlotte Stoddart: Finally will our bloggers be posting about Saturday's conference? Jennie Rohn

Jennifer Rohn: I think I will. I feel a bit out of my depth because they're so many people they're all live blogging and they're twittering even as we speak they're busy typing in and I don't know how much they can add. I definitely have thought about things differently after hearing some of these people talk and it's really nice to put faces to names.

Charlotte Stoddart: Look out for Jennie's blog posts and other conference musings on http://www.network.nature.com.

Adam Rutherford: Charlotte reporting on Europe's first ever science blogging conference.Jingle

Kerri Smith: Next up, a team of astronomers and their new toy. Here's Geoff.

Geoff Brumfiel: At the centre of the Milky Way is a super massive Black Hole that weights about 4 million times as much as the sun. Astronomers would love to get a look at it, just two problems. First it's very, very small and second it's black. So they've had to settle for the next best thing; a clear image of the gas and dust falling into it. Even that can be difficult, but Sheperd Doeleman of MIT and his colleagues have done so using a network of radio telescopes. I called him up to learn more. Nature 455, 78–80 (4 September 2008)

Sheperd S. Doeleman: Well, for a long time it has been known that there are probably Black Holes very, very massive Black Holes millions or even billions times the mass of our sun in other galaxies, and about 30 years ago, the same kind of source was discovered in the centre of our galaxy the Milky Way. And one of the holy grails of the field has been instead of just inferring the size of this black hole through the motions of things around it, I actually tried to image the emission of matter as it falls in just at the edge of the Black Hole, just before it disappears from our view entirely.

Geoff Brumfiel: So what's so difficult about imaging matter as it falls into a Black Hole?

Sheperd S. Doeleman: Well the size scales are extremely small, even though the Black Hole weighs 4 million times the mass of our sun, it's still very, very small on the sky, but it is 25,000 light years away. So you need to telescope with extremely good resolving power and that's what we did. We created what we call a virtual telescope combining radio telescope to different parts of the country and in Hawaii to give us that angular resolution that we need.

Geoff Brumfiel: And how does having all these telescopes that are so far apart actually help you to take a clear image?

Sheperd S. Doeleman: Well the angular resolution or the resolving power of any telescope is really equal to the distance between those telescopes. To put it in perspective, we can see details with these telescopes they're about a 1000 times finer than the Hubble space telescope can see.

Geoff Brumfiel: Well, so that's pretty impressive and I guess if I'm reading this paper right, what I'm given to understand is you manage to find something smaller than you what thought the Black Hole was right?

Sheperd S. Doeleman: Right, right. So what happens is when you get very close to a Black Hole, the gravity is so extreme, that even light gets bent and because of that even the smaller structure around the Black Hole, the so called event horizon, the radius inside of which light can never escape, so just outside, of that radius, the size we see of that region goes down to some minimum size and the size that we observed with this new telescope was actually smaller than that minimum size. So that told us that we're not looking at a large of blob of emission surrounding the Black Hole, which we would have seen to be larger than the size we saw, but probably what we are seeing is we're seeing a region of emission that's off to one side of the Black Hole.

Geoff Brumfiel: So wait a minute, you're saying then that astronomers have been looking at the wrong thing basically, is that right?

Sheperd S. Doeleman: Well, we're looking at something that is extremely close to the Black Hole and when we think about a Black Hole, are, just that, they are black, light can never escape them, so we can never see the Black Hole itself, all we can see is the effects that the Black Hole has on the matter immediately around it and so in this case the matter is just outside the Black Hole and we're seeing in some sense a shadow of the Black Hole and there's light coming from around the edge of the Black Hole and that was going to tell us a huge amount about Black Hole physics and testing the theory of general relativity in the strong gravity case.

Geoff Brumfiel: So where do you go from here. I mean, how do you take this forward?

Sheperd S. Doeleman: Well, we're right where we want to be actually. We are kind of at the sweet spot, because you need to go to high frequencies when you observe the galactic centre and that's because there's lot of intervening gas that causes the image of the galactic centre Black Hole to be blurred. That's only when you get a high frequencies, they're able to really penetrate that far and the thing to do now is to get more telescopes, but also we want to go to higher frequencies where we can penetrate that fog even better than we can now and get higher angular resolution. And the goal of course is to get enough telescopes so that we can actually make an image of the matters that's swirling around the Black Hole and conclusively show the receding signatures that only a Black Hole would leave behind. This is one of those very interesting experiments, where we've seen the tip of the iceberg and there's a really bright future for extending this work. A lot of times in science one scratch's ones head, about how will we make the next step? In this case, we have some very exciting results and I think it is pretty clear how to proceed and we're extremely excited about doing that.

Adam Rutherford: Sheperd Doeleman there, talking to Geoff. Finally this week, a moth with a quite repulsive range of signals. Here's Charlotte with more.

Charlotte Stoddart: If you're an insect, one way to protect yourself is to produce chemicals that make you taste nasty and then advertise your unsavouriness to would-be predators. Most insects display just one kind of warning signal, but tiger moths have two: bright colours to deter birds and ultrasonic clicks for bats. Marie Nydam from Cornell University in New York has been looking into the evolution of this dual alert system and I called her to find out more. Nature 455, 96–99 (4 September 2008)

Marie L. Nydam: What started this out was most studies of warning signals look at one specific predator and a warning signal directed at its specific sense. But we know very little about the evolution of warning signals when prey groups have more than one signal, so we call them multiple warning signals. So tiger moths have the visual signal and the acoustic signal and we are interested in how these signals evolved. There are two different hypotheses one is that both of these signals evolved towards a single predator. So a bird might see a visually defended moth and then the moth would also present a sound at the same time and both of those warning signals might help the bird learn faster than just the single warning signal and the alternative hypothesis is that each different warning signal evolved in response to a very different predator. So in this system, what's nice is that the tiger moths have two distinct predators, the birds and the bats. So we are looking to see whether these warning signals evolved towards these multiple predators or both warning signals evolved to act toward a single predator.

Charlotte Stoddart: And what did you find then?

Marie L. Nydam: So we found support for the predator-specific hypothesis. The nice thing about the system is that tiger moths, each species has a specific emergence time, so throughout the summer these species are emerging from pupa and they became adults and fly around and each species emerge either later in the summer or earlier in the summer and birds are active throughout the entire summer. So any species that emerge at any time is going to encounter a bird; but bats are only active later in the summer, so later emerging moth species are going to encounter bats. And tiger moth species also have species specific times when they fly, some fly during the day and some fly during the night. So each species is going to encounter birds or bats more often depending on when they emerge and when they are flying day or night. So we wanted to see whether the risk of different predators was correlated with a specific warning signal that these moths actually produce and we found that they were correlated more conspicuous moth, white moths and moths that had these warning colourations are more likely to fly during the day. This makes a lot of sense because visual signals and these conspicuous signals are directed towards birds which are active during the day. And the other thing we found in support of the predator-specific hypothesis is that moths that emerge later in he summer are more likely to produce these clicks, more likely to be acoustically defended against the bats and this makes sense because for later in the summer, you emerge the more likely you are to encounter a bat.

Charlotte Stoddart: I see so these moths warning signals are very finely tuned to that predator senses. I mean what's this at all surprising in this finding. It sounds sort of quite commonsensical to me.

Marie L. Nydam: It is very commonsensical and we were happy to see these results because it confirms what we already know about predator-prey relationships, but no one had actually tested these ideas in a multiple predator system.

Adam Rutherford: Marie Nydam ending that report by Charlotte. That's all from us this week. Remember you can go to http://www.nature.com/podcast for more information and to listen to the other podcasts from Nature.

Kerri Smith: Tune in next week for the second of the US elections special podcasts on Biomedicine including stem cells and bioterrorism.

Adam Rutherford: And they're finally pressing the big red button on the Large Hadron Collider - we sent Geoff to Geneva to discover whether we will find the Higgs Boson or will it simply be the end of the world as we know it. This is the Nature Podcast. I'm Adam Rutherford.

Kerri Smith: And I am Kerri Smith.

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