JOE PALCA, host:
This is Talk of the Nation Science Friday from NPR News. I'm Joe Palca. Ira Flatow's away.
Scientists say they have a new way to track animal populations. It doesn't involve micro-chips or radio collars. It turns out viruses can tell us a lot about the animals they infect. A new study in this week's Science magazine looks at a cougar population in western North America that's infected with a virus called FIV, Feline Immunodeficiency Virus.
Here's the premise, the virus spreads from cougar to cougar. Once it's inside the animal, it starts to acquire genetic changes. So, different populations of cougars have different versions of the virus. By tracking the virus the scientists can essentially track the cats and learn more about their populations. It's a potentially useful tool for wildlife managers.
Joining us to talk about the research and what it means for wildlife conversation is the lead author on the science paper, Dr. Roman Biek. He did the research while he was a PhD student at the University of Montana. He is currently a post-doctoral researcher in the Department of Biology at Emory University. He joins us by phone from Knoxville, Tennessee.
Dr. ROMAN BIEK (Biology, Emory University, Atlanta, Georgia): Great to be here.
PALCA: And I'd just like to say that if you're interested in more information on this topic and the others we'll be talking about this hour, you can go over to our website, sciencefriday.com, where you'll find links to information about the topics. So, the first question Dr. Biek is where did you get this idea of tracking an animal population using a virus? Was that yours?
Dr. BIEK: Well, actually it was my PhD advisor, Dr. Mary (unintelligible) at the University of Montana, who came up with the basic idea together with people at the University of Auckland actually. And so they looked at viruses, and recognized how rapidly viruses are evolving, actually more rapidly than any other organisms we know of. And so given this rapid evolution, they accumulate variations so fast. We could use that potentially to tell us something about the host, which evolves much more slowly. So, especially when we talk about things in the recent past about, sort of, what's going on in real time, the virus could become a really useful tool for that.
PALCA: I just want to remind our listeners that they're welcome to join this conversation. Our number is 1-800-989-8255; that's 1-800-989-TALK. So, I mean, what was the idea? I mean, if you're able to track the virus, what kinds of questions can you ask about the cougars in this case?
Dr. BIEK: Well, I came at it from more of a population, ecology and conservation angle and I was really interested in finding new ways to see how recent changes to the landscape have affected animal populations. So, with the cougars we thought, well, the virus may tell us something about whether cougars are currently able to move freely through the landscape, whether basically the landscape is still permeable, and also maybe to check in the future again whether connectivity is still maintained. The important thing here is that it's the current changes to the landscape that are important so we really want to know what's happening to cougars currently, not in the past, and it seems like the virus was the right tool to try that.
PALCA: What kind of changes are we talking about?
Dr. BIEK: Well, for example it's, you know, highways or developments or any of those changes to the landscape that may impede movements of animals, and cougars were just the system that we were working on, but we thought that in general this idea could be applied to many other taxa as well. We just chose cougars because we knew this system, this particular virus that infects them. So that's what led to that, but we're really thinking of testing something that could be applied to a wide range of taxa and to see, basically, provide a new means to test whether they're affected by habitat fragmentations or the reverse; to see, if you implement a habitat corridor, whether it is used by animals.
PALCA: Because just looking at the map of the range, we're talking about western Montana and up into British, well, what's north in Canada?
Dr. BIEK: Alberta, British Columbia.
PALCA: Alberta, British Columbia. I mean, these are not areas that are heavily populated. You're seeing enough changes to actually see changes in the virus pattern in the cougars even in these sparsely populated regions?
Dr. BIEK: Well, I have to maybe step back here for a minute because this is sort of the application that this tool could have in the future.
PALCA: Oh, I see.
Dr. BIEK: Right now we're not seeing that the cougar populations are fragmented. Actually we see that they're moving quite a bit, but even though they do, we see that the viruses haven't quite taken on a distribution that it could have, given how mobile cougars are. So that's actually an important aspect of our paper is that the virus contains a recent signature of cougars actually being much more rare in the landscape and that cougar populations have just recently rebounded and that the virus really contains a signature of this rebounding of the cougars. So, that's another important application of this that the virus tells us something about what happened to the cougar population in the recent past that the close population actually has increased so dramatically recently.
PALCA: And I guess I should ask, I mean, Feline Immunodeficiency Virus, that sounds like the AIDS virus to cats. Is it causing illness in the cats? Do all of them have it?
Dr. BIEK: Yeah, that's a very good question. The name comes actually, FIV was first found in domestic cats and it does cause a form of feline AIDS in domestic cat species, but in wild cats we see related forms that are specific to individual cat species. So, there's a cougar FIV, there's an African lion FIV and in those species we don't see disease, so it doesn't seem to cause them any harm. They probably have (unintelligible) with those viruses for a long period of time.
PALCA: So, I guess I'm still a little unclear, if the virus is changing clearly, but I mean, all you really know when you look at two different strains of the viruses, well, one's different from another. So, how do you actually use that to track the animal? How does the virus change tell you something about where the animal's been?
Dr. BIEK: Well, it doesn't tell us where the individual animal has been but we can look at the distribution of different viral, we don't call them strains, we call them lineages, but it's genetically distinct types of the virus and we can use genetics to distinguish those. And if we look at the distribution, then individual virus lineages are only found in certain areas, so it's almost like you can tell where a cougar is from by which virus it's infected by. And given that cougars are really mobile and we know that their movements aren't restricted very much currently, the question was basically why are the viruses not occurring anywhere.
If the cougars move around so much why don't their viruses? So, we think that this is really related to cougars being rare in the recent past where they probably survived in certain refugea and a lot of the viruses disappeared, they became extinct from a lot of areas, but where the viruses survived they were able to expand again. And actually we see evidence of this spatial expansion in the virus population that coincides with the period when cougar populations expanded again.
PALCA: I got it. Okay, let's take a call now and let's go to Matthew in Washington, D.C. Matthew, welcome to the program.
MATTHEW (Caller): Hello. Thank you. I was wondering what your, I might have missed this, but I was wondering what your methods for obtaining strains of a virus are and how this is more efficient than just simply tracking the cats themselves?
Dr. BIEK: Okay. Yeah, so we used genetics. We basically, we sequenced a fairly big part of the virus genome and we use the virus sequences to basically create a family tree of all the cougar viruses we found in the area. And then within this tree, we found eight groups that we could readily distinguish, and then we looked at the distribution of those groups, but we also used, the tree actually contains a lot of information about what happened to the virus population recently, whether that virus population was increasing or decreasing for example. So, there is statistical tools available to analyze the genetic data to inform us about things like the dynamics of the virus Yeah, and then we matched it up with the spatial distribution.
PALCA: Okay. Now the question about wouldn't that tell us compared to marking the animal itself, those studies exist and of course we can do that. We could put radio collars on them but you're very limited. I mean, it's an expensive technique and usually you can only do it in a certain area, because you have to go around and find those animals again with the radio collars. And so once they leave the area you may not see them again.
There's alternatives, which are GPS collars but those are very expensive and you're even more limited to the number of animals that you can mark.
PALCA: Okay, Matthew, thanks very much for that call. Actually I was wondering, I mean, did you yourself go out and how do you get enough, what kind of sample do you get from the cougar to be able to tell what kind of virus it's got?
Dr. BIEK: Yeah, I did not get out in the field myself. We had a lot of people helping us with this. We had researchers that had ongoing study projects in Yellowstone and other parts of Montana and south of there. So we got a lot of samples from live cougars from them and those are usually blood samples.
And then we worked also with hunters in Helmsman, so cougars are hunted in Montana and actually the entire area that we sampled. And so we worked a lot with those people that kill cougars and told them which kinds of samples to collect. And there's certain types of tissue that we could use and we also gave them a certain type of filter paper that they can basically blot a little blood on. And then we could analyze the blood for the virus.
PALCA: Sounds to me a lot safer to sit in a lab than to cozy up to a cougar.
Dr. BIEK: Yeah, I miss that aspect of the work sometimes but actually I did go out in the field with people and that was very exciting. It is a lot of work, so I really couldn't have done both, I think, so.
PALCA: Yeah, so do you see any future application for this for wildlife management?
Dr. BIEK: Well, yeah, we definitely think that this could be applied to other cats and that it could be, it's certainly a complimentary tool. It won't replace any of the tools that we have available but it may be a complimentary tool in to look at issues like habitat fragmentation and connectivity. But I think that the limiting factor here is really that we know very little about infectious organisms. And especially those that don't cause disease; we have little reason to look for them right?
So we really have to look harder to find other infectious organisms that we could use in this context. But I also think the bigger picture here is that we really don't know very much about how viruses and microbes are transmitted, how they are moving through animal populations in the wild. And that goes beyond just using the virus as a genetic tag as we did in our study.
But if you think of you know those viruses that are actually a public health concern, we're also really interested in how do those viruses spread and how can we learn about the patterns of spread and over what time scale, over what spatial scales does the spread occur.
PALCA: Yeah, I'm just quickly, do we know how the virus spreads from cougar to cougar?
Dr. BIEK: Yeah, we do and it's important to know that it requires direct contact between cougars. So we know that mothers can pass it on to the offspring and we also know that they can pass it through contact. Probably biting, potentially mating but they have to be in close contact. I mean we all know that you can only transmit HIV for example through exchange of body fluids and it's very similar in cougars.
PALCA: Dr. Biek thanks very much. I' m afraid we've run out of time. Dr. Roman Biek is a post doctoral researcher in the biology department at Emery University. Thanks for talking with us. When we come back we'll talk about the new field of evo-devo. So stay with us.
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