Wildlife Conservation Society researcher Ullas Karanth talks about his July, 2016, Scientific American article on state-of-the-art techniques for tracking tigers and estimating their populations and habitat health.
Wildlife Conservation Society researcher Ullas Karanth talks about his July, 2016, Scientific American article on state-of-the-art techniques for tracking tigers and estimating their populations and habitat health.
Steve Mirsky: Welcome to Scientific American's "Science Talk," posted on June 16, 2016. I'm Steve Mirsky. On this episode..
Ullas Karanth: And the tiger would come out right under me, and I would be not in a blind; I would be standing on a branch just 15 feet off the ground. And it's quite a scary feeling.
Mirsky: That's Ullas Karanth. He's the Wildlife Conservation Society's Director for Science-Asia. He's also affiliated with the University of Minnesota, as well as with India's National Center for Biological Sciences in Bangalore and Manipal University. And he has an article in the July issue of Scientific American called "Tracking Tigers." Karanth was visiting New York City recently. On June 8, I met with him at the Wildlife Conservation Society's Manhattan offices on the grounds of the Central Park Zoo.
Tigers are so charismatic. And yet, based on your article, for a long time we haven't even been able to accurately tell how many there were in the world – wild tigers, obviously, not those in captivity. And the methodology, the older methodology, was apparently very poor.
Karanth: Yeah. All the methods used to count tigers, historically and now, have been poor. And it's not a surprise, because tigers are extremely rare. They exist at very low population densities on the ground. They are wide-ranging. They are very secretive. They avoid people. So, they're not an easy species to count.
So, people have used naive methods of different kinds, using just tracks in different manners in India, Russia, and Nepal, and subsequent to 2005, some attempts to use camera traps, which I had actually developed in the '90s. It took about 20 years before it came into more widespread practice in the tiger world. Even now, the camera traps, used properly, can give good, really good counts and estimates for small areas where tigers are found in high densities – the so-called source populations. But when you're looking at large regions, whole states, entire landscapes or countries, you can't put camera traps out on that scale. It's not practical.
So, what people have been doing is then trying to either go back to using tracks—tracks alone—or trying to use some models that link the tracks to the camera trap estimates. Now, these models are highly problematic, the way they have been used so far. So, they—even they haven't given any good results. So, these big numbers of tigers that people talk about for whole countries, regions, states, are essentially not robust at all. They're based on very poor methods.
And my point is they're not necessary. What is necessary is monitoring tigers in these source populations very closely because they are like patients in an intensive care unit. So, each population has to be monitored using the best methods most rigorously. These big overall numbers around which people make so much hoopla, they don't have much use actually.
Mirsky: Yeah, you make the point in the article that in some ways we might not even need to know what the exact population of the world's wild tigers are. As you say, it's more important to know in these crucial areas what it is.
Karanth: Exactly. These whole numbers don't lead to any effective action or anything that you can do on an individual population. And sometimes they breed euphoria; sometimes they take you off course. Some states in India have reported in four-year or eight-year spans increases of 200 percent, which is biologically impossible. And they make some conservation agencies set these unrealistic targets, saying that, "Okay, we had the tiger summit with Mr. Putin presiding in 2010, so in ten years after that we should have twice the number of tigers." They become political gestures. They stop being objective tools for conserving tigers, and this concerns me.
Mirsky: There's one fascinating piece of methodology we haven't talked about, and that's the tiger pattern identification. So, before we go any further into policy, I think listeners would be really interested in that.
Karanth: Yeah. Essentially, if you have to count tigers, the old way of saying "I can recognize their tracks" doesn't work, unless the animal has a really crooked foot or something like that. The best way to recognize them is from photographs. Each individual is unique. And this is not special to tigers: This is true of leopards, zebras, many, many naturally-marked animals. The coat patterns are so characteristic, almost like human fingerprints, and you can identify an animal without any doubt.
So, the next question, then, is how do you get those pictures? There are very few places in India where you can go around and photograph tigers, because they are shy and secretive. Even in the most habituated tourist reserves, where you have these habituated tigers that you can see, it's only a fraction of the—a small fraction of the population. Most tigers are still shy and hiding. So, that takes us to the next step of having automated cameras that are scattered across the park, or a reserve, and which are tripped by the tigers themselves. And that's a whole technology that has a century of history – over a century of history—these automated camera traps that animals take their own pictures.
And for a long, long time it wasn't practical. For example, an Indian forester called F. W. Champion first used them to photograph tigers in the 1920s. But for 35 years of efforts he got nine pictures of tigers. This was very primitive equipment with magnesium flares and a wire that the tiger tripped, and those things don't work.
What really changed was in the '80s, when I was in graduate school, cheap cameras that were rigged up to cheap electronic tripping devices came. These actually came in to help US deer hunters find where the big bucks are and go and shoot them. The original purpose was different. But I said, "This is a smart way to count tigers." So, I started experimenting with this in 1990—took some of these units, put them out in my—study area, and I was able to get good tiger pictures at very, very reasonable costs, and that worked under field conditions reasonably well.
So, once you get these pictures you have to be a little careful. The left and right flanks are different, so you need two cameras. And the stripe patterns can be compared visually. I tested it out on my daughter, who was 12 years old, and she could tell the tigers apart. And this is not zookeepers, you know? They recognized the tigers from stripes.
So, the issue then was a more complicated one. Okay, you kept your cameras. You got your, let's say, 50 tigers in your cameras. But many of the animals are not trapped. You haven't got them. So, how do you get an estimate of that? And that to me was the real challenge. And I started exploring the statistics behind this, the modelling behind this, and I was lucky to interact with a very, very accomplished statistical ecologist called James Nichols in the U.S. Geographical Survey, who was a real pioneer in the developing of these methods. And it's very interesting that the idea that by taking the pictures in some sorts of sequential samples, repeatedly doing this—so, not rather than once—you can estimate the proportion of animals you have caught. So, you not only get to know that you have caught 50 animals, but that you have got half of all the animals that are out there. You missed half of them. So, that way you can say, "Okay, I got 50, but I got only half of the animals that are out there, so the total population is 100."
So, this is really the power. And the original idea is so simple, very powerful, and it goes back to the famous French mathematician, Pierre Laplace. And from his time, statisticians and ecologists have developed these models to such a level of sophistication now, I had a ready tool, both in terms of a ready camera that could take tiger pictures cheaply, and also these wonderful models, with whom Jim and I have been working for the last 25 years or so. So, it's been fascinating.
Mirsky: In the article, you talk about one way to look at the statistical method to figure out the population based on this is if you had a jar full of marbles, and you dip in and you take out a few and you mark them, then you put them back in the jar and mix them all up again, then dip in again and see how many of the same marbles that you've already pulled out you pull out again. And you're able to really tell – get a good estimate of the entire marble population that way. And the same thing with the tigers.
Karanth: Exactly. That was Laplace's idea in the 17th century. Then, a Danish fish biologist developed it to estimate fish in the late 19th century. And then, an American biologist—Lincoln, Fred Lincoln—developed it to estimate ducks from the number of banded ducks shot. And the methodology has developed incredibly well. Now it's so smart that you can use it on the fact that, unlike marbles, not all tigers mix. They are territorial; some of them are more likely to be caught. It can account for that. Some animals may be trap-shy. They may not like being photographed and become less likely to be caught next time. It can account for that. Whether sampling in different season affects capture probabilities can be accounted for. So, this is a very neat area of development.
The other add-on was that as you accumulate a lot of tiger photos—hundreds and thousands—and then leopards, which are even more complicated, eyeballing and identifying, comparing all of them—because you have to compare all of them to rule out duplication—becomes very tedious. So, I was able to work with mathematician Lex Hiby in the U.K., who had developed an automated pattern-matching software. So, instead of painfully identifying each photo and comparing it to each one, this pattern-matching software would do a very quick survey and isolate the top five matches, and then you just had to look at those.
So, these were two computer applications that really—modeling and computer applications that really helped.
Mirsky: So, using all these techniques, you've been able to really figure out in these protected areas what are the ranges for a typical tiger, what the food requirements are. Now, again, that might be the same as it is for a tiger in an area that's not protected, because it looks like the population densities are probably higher in the protected areas, because they're smart: They stay where they're in better shape.
Karanth: Yeah. They stay where the food is.
Karanth: So, the protected areas have piles of tigers in a landscape where they are otherwise very thinly described. All these cats are piling up because that's where the cat food is. There's a lot of prey there in these protected areas, because they've been protected for 30 or 40 years, so there's enough deer and pigs for the tigers to eat.
The camera trapping tells a lot about populations – like, the numbers at any point in time, densities, how those numbers are changing over time. And if you use the right models across the year, it tells you what proportion has survived from year to year, what proportion of new tigers are entering the population. You get a complete picture of their population dynamics, or how their populations change across space. And if you do it long enough in multiple sites, you start getting movement between these sites. Animals have moved from one site to the other. Young animals go 200, 300, 400 kilometers. You get that.
What it doesn't do is intricacies of behavior, like how they raise their cubs, how do they exactly hunt, how do they stalk prey, how much food they eat. These questions require a different set of tools, and basically radiotelemetry. You've got to catch them, put radio collars on them, follow them, watch them, see what they do, see what they kill, see what they eat. That's a different set of questions about individual behavior. But the population stuff works very well with camera traps.
Mirsky: Which you've also done. When you actually—you're sitting in a blind with a sedative dart gun and here comes the tiger. People can go their whole lives without seeing a wild tiger who live where they are. What is that like when you see the tiger with your own eyes? What's the—or, are you just so concentrated on your job right then?
Karanth: Well, see, the way—there are different ways of catching tigers. For example, in Russia, where there are not many tigers, no elephants, you can put snares and catch them. In areas where they are hungry, they don't have enough wild prey, you can put traps and they enter traps. But the situation I was working in in the early '90s was a prey-rich area with lots of wild elephants, a lot of tigers, and they would not enter traps. And I was too worried to catch them in snares because some other tiger or an elephant may get them before I got there.
So, we—my professor at that time in the University of Florida—Sunquist, Mel Sunquist—had originally developed this technique in Nepal of modifying an Indian and Nepalese hunting technique, which was used actually to shoot tigers, to capture them. We modified the method. It involved putting out bait which the tiger would kill—which is usually, typically a small animal, a domestic animal the tiger would kill. And we used to put a little radio collar on the bait so we knew where the tiger was sitting with the bait.
After that, we went with a team of 15 trackers and 3 tame elephants and hundreds of meters of white cloth, and erected a stockade around the tiger with just a gap for it to exit. The tiger is not aware that this stockade is being erected. Then I would go and sit in a tree. So, it was not sitting in a blind at random. So, it was at the mouth of the stockade. And then, the rest of the team would go and quietly approach the tiger, which would avoid them—get up. And this cloth barrier all around it was like a psychological barrier. The tiger could jump the stockade easily and rip it apart. And in fact, it never worked with leopards because they would simply sail over this cloth. They are much smarter than tigers. And the tiger would come out right under me, and I would be not in a blind; I would be standing on a branch just 15 feet off the ground. And it's quite a scary feeling. The tiger is coming right there; all you have is a pneumatic air gun with a dart which won't stop the tiger. It's kind of exciting. It's really exciting. And you just hope that it's not a female with three small cubs.
Karanth: Otherwise, you're okay. In fact, even if it looks up, it'll just run away. It's not going to attack. They don't do that; they're very scared of humans. But if she's a tigress with small cubs, there's a chance she may come after you.
Karanth: So, I was always worried about that.
Mirsky: Yeah, I bet. Ultimately, all this data collection and analysis has to go into informing policy decisions. So, what's the bottom line, really?
Karanth: You're absolutely right. The bottom line is all this knowledge can advance scientific understanding, which is a noble goal. But to me, the personal satisfaction is only if it then ends up helping the tigers, saving tigers. So, in that sense, key insights from research are really important. Because the tigers today occupy just seven percent of their historic range 200 years ago. Their range has contracted. For a long time, the idea was that this contraction of the range was primarily because of people hunting tigers and particularly because of the recent upsurge of tiger trade. But the research development of the techniques to count prey and tigers and doing studies in different sites across India with high and low prey densities show very clearly that the number of tigers is linked to the number of prey in a very, very strong relationship. Like, for every 500 prey animals there can only be one tiger.
So, this then made us realize that the contraction of the tiger's range and the fact that even the forests which could hold tigers today is empty of tigers is primarily a consequence of the prey being hunted out rather than the direct killing of tigers. Direct killing of tigers is a serious problem, but it's not the only problem.
Now, if local people are hunting the prey and that's driving the tigers to extinction, catching a big trader in China is not going to help that problem. So, this will require a completely different set of responses that are local patrolling intelligence. So, this is how science has to go mainstream into management and policy. And it is possible to do it, and this tiger-prey relationship was one. And people were looking at tracks and trying to count them, which simply didn't work, but we can use track surveys over large landscapes to know where tigers are, where populations are getting established. So, some of the work led to very innovative use of tracks—not to count them, but to figure out how they are spread over the landscape. So, these—and handling conflict situations. Many of the techniques used for capture are useful when you have tigers that are in a problem situation.
So, to me, this link between science and application is really important, because conservation is exactly like medicine. It's exactly like engineering. It is using a basic science to solve a problem. So, to me, that link is critical.
Mirsky: Tigers played a very important role in your cultural upbringing. That's—you talk about that in the article too. That's really interesting how iconic they were when you were growing up in India.
Karanth: Tigers, in fact, wherever they have occurred historically, if you look at the religion culture and iconography of Hinduism, Buddhism, and Islam—the three big religions that kind of cover the tiger range—tigers are very, very powerfully present everywhere. But I was particularly lucky because in the state of Karnataka and the three southern states on the southwest of India—the Western Ghats, the Malabar landscape where I grew up and I've done most of my research—it is so deeply embedded. We have many, many local deities, gods, holy men who are worshipped who are supposed to ride the tiger.
Then, there is the ancestral worship – kind of a pre-Hindu cultures, where again there are shrines to the tiger, and where it is—animals are sacrificed to please the tiger god. Then you have also an annual festival where men paint themselves in varnish paint—I mean, it must be killing; it's lead paint – and for ten days they are in this varnish paint doing this fabulous tiger dance. There is music to it. The steps are like that of a real tiger raising its cubs or hunting.
So, I kind of grew up in all this. So, on one side was my Hindu culture, the native culture infused with tigers. On the other side was my father, who was a well-known writer and also a popular science writer who had a deep interest in natural history, which is uncommon in India. People are generally – his generation, nobody was interested in natural history. So, he read me tiger hunting tales. He brought books and—you know, natural history. So, I was very—as I—this natural fascination was nurtured further by reading almost—you know, the British tiger hunters, there were dozens of them who wrote hundreds of books. So, I read them all.
Then, in 1965, as an engineering student—I had gone into engineering because there was no career in those days in the mid-'60s when you came out of school, there was no career in conservation. I was in engineering. And the Life Magazine carried an article by George Schaller, who was an eminent scientist of WCS who had done the first scientific study of tigers in 1964, and he wrote a three-page article but with some spectacular pictures of tigers. And that was incredible because suddenly I realized that all these hunting tales, these folk talks, the tiger—that all paled in significance when you looked at what Schaller did. He took the tools of modern science and, really, in a span of one and a half years, he got to know more about tigers than all I had read in those 300 books. So, I—it was really like shedding a cataract. You know? I said, "This is what I should be doing. I shouldn't be doing engineering. I should be reeducating myself, studying biology and using these tools to take the study from beyond where Schaller had started."
And I was lucky in 1983 to meet with Mel Sunquist, who was the first person to go beyond Schaller and use radio tracking on tigers in Nepal. He was a professor in Florida and I encountered him in a conference. He took me under his wings and I ended up getting trained with all these techniques, and meeting Jim Nichols and learning the statistics. It was—I was already—and then I met Schaller again. He was visiting Florida and he hired me. Schaller and Bill Conway hired me to work for WCS. So, it's been a good ride since then.
Mirsky: That's it for this episode. Get your science news at our Web site, www.scientificamerican.com, where you can check out the coverage of the most recent LIGO gravitational waves findings, headed by Clara Moskowitz. And follow us on Twitter, where you'll get a tweet whenever a new item hits the Web site. Our Twitter name is @SciAm. For Scientific American's Science Talk, I'm Steve Mirsky. Thanks for clicking on us.