In early 2004, we believed Rajasthan's Sariska Tiger Reserve had 16 to 18 tigers.¹ But curiously, visitors had not spotted one for several months. Forest officials defensively suggested that the tigers had simply "gone to the hills." Whispers kept growing and, in December, news broke that tigers had likely been poached to extinction. This was a global scandal.

After the fiasco, India's top federal agency, the Central Bureau of Investigation (CBI), launched an investigation, and the then Prime Minister Dr Manmohan Singh formed a task force to assess Project Tiger, India’s flagship tiger conservation initiative. The experts looked beyond Sariska and identified several systemic issues in India's tiger conservation.

Many things needed to change, but one of the most urgent was the tiger-counting methodology. After all, the Sariska episode raised a foundational question: how do we even know how many tigers are there in India? Counting is a difficult enough problem for a decadal human census, when most people have household addresses and can answer questions. How do you count big cats that roam in remote habitats?

How did we count tigers back then? Why did we do it that way? How has that changed, and what remains to be done? The story of how India’s methodology of counting tigers evolved is an interplay of colonial baggage, scientific prowess and innovation, indigenous knowledge, statistical mastery, bureaucratic clashes, geopolitics, and national security.

E.P. Gee, a well-travelled naturalist, estimated that India had about forty thousand tigers at the beginning of the twentieth century, but only about four thousand remained in 1964. Jim Corbett, the famous big cat hunter, estimated the number to be two thousand in the mid-1950s. Others came up with similar estimates and while most of them were just guessing, it became clear that something needed to be done quickly to save the tigers. The first step was to get an estimate of the number of remaining tigers more systematically.

Kailash Sankhala, the first Director of Project Tiger, consulted forest officers from around the country and estimated the tiger population at about 2,500 in 1969. Then, things progressed quickly: India became a member of the International Union for Conservation of Nature in 1969 and its tenth general assembly was held in Delhi in the same year; tiger hunting was banned in 1970; the union government enacted a law to protect wildlife in 1972; and Project Tiger was launched in 1973.²

After the 1969 estimate, based on foresters' knowledge of areas under their supervision, a more comprehensive estimate of the tiger population was still needed. Forester S.R. Choudhury, who grew up in the forests of Odisha and had previously conducted a tiger census in the state in 1966, took up the national task. Like many early conservationists, he was a hunter and much of his knowledge came from years of tracking tigers.

Given that tigers were territorial animals, Choudhury devised a simple scheme: divide the forest into zones, survey each for pugmarks and other signs of tigers, and talk to local people about their tigers. According to him, pugmarks were the most frequent and numerous evidence that a tiger left behind in the forest. He maintained that the possibility of a tiger not abiding by its territory was very rare. He compared the pad of a tiger to a wheel-tube as opposed to, say, a horse’s hoof. The size and shape of the pad on the ground are dependent on the tiger’s weight, gait, and the soil condition, meaning that there were enough qualifiers for each pugmark to be unique.³

The premise was straightforward: tigers, including their sex, could be identified as individuals by their pugmarks. If we could collect and count pugmarks from tiger territories, we could get a reasonable estimate of tiger numbers in the country.

Rigorously testing this methodology and finding a way to collect pugmarks remained a major challenge. Choudhury tested his methodology and found that when he and his ten students measured the same pugmark separately, their measurements did not match. The quality of the pugmarks also depended on soil conditions.

He came up with two solutions. First was a 6 x 8 inch piece of thin, clear, framed glass with four adjustable short legs at the corners of the frame, called a ‘tiger tracer’, which could be used to trace pugmarks for review by more experienced eyes. The second was ‘pug-impression-pads’, where a thin layer of powdery soil could be added to roads to produce better quality pugmarks regardless of soil condition.

For 18 days across March and April in 1972, selected forest officers from tiger ranges across India attended a training session with Choudhury. They observed pugmarks, learned how to use the tiger tracer, and filled the counting sheet. After the training, they fanned back into their respective reserves with counting sheets in local languages and conducted their own training for the local staff. The smallest unit of the census in 1972 was a ‘beat’, an assigned area of the forest supervised by a ‘beat guard’. Once trained, these beat guards walked their beats to count tigers. ⁴​⁵

Data was collated at the divisional level, then state level and then sent to Delhi for national-level processing.⁶ The first national tiger census of 1972 concluded that only 1863 tigers remained in the wild in India.⁷ A gargantuan drop from Gee’s 40,000 at the beginning of the twentieth century estimate.⁸

The methodology, however, also had detractors from early on. Dr S. Dillon Ripley, associated with the Smithsonian Institution in Washington, argued that the method was deeply flawed, too subjective, and impossible to validate. He did not believe that tigers could be counted by pugmarks. However, it was easy for Indian foresters to dismiss Ripley, who had wanted the Smithsonian involved in counting Indian tigers but was spurned by the Indian government.⁹ Why were Ripley and colleagues not welcome in India?

Ripley was no stranger to India. He had done extensive research on the birds of India with the country's foremost ornithologist, Dr Salim Ali of the Bombay Natural History Society. Indian independence made it harder for British scientists to come to India, and Europe was more interested in rebuilding itself than funding wildlife research after the Second World War.

Consequently, the Americans replaced the British in many ways, and Ripley worked in India from the 1940s to the 1980s.¹⁰ They had more funding, growing enthusiasm, as well as expertise in ecology and wildlife research. At the time, India was not in a position to fund wildlife research, with most post-independence resources going into development and industrialisation.¹¹

American scientists brought the latest technology and the know-how to use it, which Indian scientists desperately lacked. This imbalance in resources and expertise, however, also led to an imbalance in the relationship that Indian scientists, especially the foresters, increasingly resented.

As India was trying to save the tiger in 1971, a war between India and Pakistan ensued over then East Pakistan (now Bangladesh). The American president, Richard Nixon, sided with Pakistan and slashed economic aid to India. In retaliation, India barred most American scientists.¹² It did not help that the military and wildlife in America were deeply entangled. Ripley himself had worked for the precursor of America’s Central Intelligence Agency (CIA), which is how he came to be in South and Southeast Asia, and the Smithsonian received funding from the American military for certain projects.¹³

Was India extending invitations to harmless bird nerds, who were somehow always interested in birds on the borderlands between India and neighbouring countries, or secret CIA agents? Media reporting furthered doubts around the Smithsonian’s intentions and projects.¹⁴ So the Smithsonian took the tiger ecology research to Nepal’s Chitwan National Park instead.

The pugmark methodology came out of these messy entanglements. According to the Indian foresters, they rejected a form of neo-colonialism or “coca-cola colonialism” to create an indigenous, cost-effective methodology based on the local knowledge of those who knew the Indian forests intimately. For now, there was no need for fancy new technology or for turning India into “Smithsonian’s laboratory.” The laboratory, however, had established itself one country over and was finding some remarkable things about tigers.

Until the Chitwan study in Nepal, tiger behaviour was mostly understood through hunting records and writings of naturalists. Scientific studies were rare, with the notable exception of George Schaller’s The Deer and the Tiger, which focused on the tiger’s ‘land tenure system’, i.e., how tigers divide space among themselves. The problem, however, was that while observing them had excited many, the tigers were only visible when they wanted to be seen. The early tiger enthusiasts were limited by scant observation.¹⁵

Like several foundational technologies, animal tracking technology came out of military technology. The invention of the transistor opened the possibility of radio transmitters that could be attached to animals without causing significant damage or change in behaviour. John and Frank Craighead started radio-collaring grizzly bears in Yellowstone National Park to design park policy as per grizzly behaviour.¹⁶ It was contentious but ultimately pioneering and paradigm-shifting research. The Craighead brothers’ students and colleagues were then involved in radio-collaring tigers in Nepal through the 70s and 80s while India continued to deny access to Indian tigers.

Radio-collared tigers allowed researchers to discover the secrets of the tiger even when the tiger was deep in the forest doing tiger things.

These studies, based on unprecedented access to the tiger world, along with other long-term research in India,¹⁷ proved the pugmark method was built on some inaccurate assumptions.

The pugmark method assumed tigers lived in pairs, that transient tigers did not venture into core breeding habitats, and that, even if they did, it was brief. Tracking tigers continuously for long periods of time in the 1970s and 80s proved that territory overlap was significant, tigers did not form pair bonds, ‘floaters’ moved around different territories a lot, and higher density areas saw more movement, not less.¹⁸

By the 1990s, scientists in India were arguing that the pugmark method needed to go. But what was to replace it? The tiger tracer was out, but so was the radio collar, because it was expensive, dangerous, and impossible to collar every tiger. How should India count tigers?

By the mid-late 80s, India still did not welcome radio collars with open arms but began showing some openness. The Wildlife Institute of India got permits to radio collar several species, including the Asiatic lions in Gir Forest in Western India, and Dr Ullas Karanth got permits to radio collar tigers and leopards in Nagarhole National Park in Southern India.¹⁹

While Karanth was a big fan of old-school hunters and naturalists, he considered their mode of research nothing more than storytelling. He was more interested in up-and-coming scientifically grounded techniques and often criticised the continued reliance on ones that had long run their course or had no business ever being in course, including the pugmark methodology.

Karanth’s most famous critique came in 1987, when he took thirty-three pugmark tracings from four tigers to a group of experts who had participated in previous tiger censuses. Out of the six experts surveyed, nobody was able to accurately guess the number of tigers, with guesses ranging from six to twenty-four tigers.²⁰

From 1989, Karanth started radio-collaring tigers in Nagarhole.²¹ Once again, tracking the animals—which required Karanth and his colleagues to climb hills and towers with receivers—gave them hard data. How many times did the tiger hunt? How many deer did one tiger need to eat in a year? What did territories look like? How much overlap occurred?

In the far east of snowy Russia in 1994, Dale Miquelle was radio-collaring Amur tigers and found their territories were twenty to thirty times bigger than those of Indian or Nepalese tigers. Karanth would solve the territory mystery by postulating that there was a relationship between tiger numbers and prey numbers.²²

Karanth’s time in America and his connections also gave him access to developing technology and techniques in the field. In the 1990s, he also experimented with camera traps but found them expensive and failure-prone until he came across TrailMaster cameras. An American engineer/hunter had perfected infrared cameras for monitoring deer populations for hunters. Karanth and other scientists started using these TrailMaster cameras for monitoring animal populations, as these were triggered electronically and were fairly affordable.²³

Two camera traps could photograph both flanks of a tiger, helping identify it by its unique stripes.²⁴ Researchers could place these cameras throughout the forest to capture photos and identify tigers individually. Voilà, a method to count tigers!

There was still the issue of ‘imperfect detection’, that some tigers would inevitably be missed. A flaw of the pugmark method was the assumption that the census covered most of the tigers or achieved a ‘total count’. But this was nearly impossible in jungles and terrains as dense and varied as India. As radio collars became more common, mathematicians and statisticians were also using their own magic to estimate populations of different animals.

Along with statistician Jim Nichols, Karanth worked out the detection probability of tigers using the capture-recapture statistical technique. In this technique, researchers identify individual animals (traditionally by physically tagging them) and then observe the population repeatedly over several sampling periods. By tracking how often the same individuals are "recaptured"—spotted or photographed again—versus how often entirely new individuals appear, statisticians can infer how much of the total population remains undetected. If most sightings are repeats of already-known individuals, the population is likely small; if new ones keep turning up, the true population is probably much larger than what has been directly observed.²⁵

Similarly, line transects had been used for a few decades in wildlife censusing, but in the 1970s researchers started giving them real statistical weight. A line transect involves walking (or driving, or taking a boat) in a straight line through a given area and recording every animal sighted along the way, along with its perpendicular distance from the line. The method assumes animals directly on the line are essentially always detected, but detection becomes less likely with increasing distance. This drop-off rate in sightings with distance allows density to be statistically estimated.

By the mid-1990s, Karanth advocated combining the capture-recapture camera-trap method with line transects to estimate tiger populations in India. It would take another ten years for a version of his methodology to be accepted.

The Smithsonian team operated out of the Tiger Tops Jungle Lodge in Nepal’s Chitwan National Park, the only tourism lodge at the time. The Tiger Tops team was adamant that the Smithsonian team not collar tigers near the lodge that routinely came to eat the bait station, because tourists would think they were seeing captive tigers instead of wild ones. Consequently, collaring Tiger 102, or ‘Dakre Tiger’, a regular at the bait station, caused a stir.

According to Ripley, Tiger Tops’ reluctance toward radio-collaring mirrored India’s stance that prevented the Smithsonian from starting the tiger ecology project in India: the belief that wildlife needed to be left completely alone, free from human influence.

However, this was not a uniquely Indian idea. Wildlife managers and scientists have not always gotten along. From the beginning, radio collars drew much scrutiny because capturing, immobilising, and tagging animals made many uncomfortable. The Craighead brothers faced significant criticism because their research undermined a fundamental American idea that nature ought to be managed in ways that keep the ‘untouched wilderness’ untouched. It also became entangled with American nationalism.²⁶

As per this philosophy, the scientists’ real job was to observe, know, and walk the land. The tagged grizzlies were described as “impure” and “contaminated”.²⁷ The grizzly bear tagging conversation quickly snowballed into a larger debate about how nature ought to be managed, echoing a decade later in India and Nepal. Like the Americans, many Indians, especially foresters, remained suspicious of technology, with an undertone of a postcolonial nation wary of foreign involvement.

Technology, then expensive and foreign, was an interventionist approach that seemed too risky to adopt. In his autobiography, Sankhala writes about taking pride in not reducing the tiger to a frog or a guinea pig. But in India, like in America and Nepal, other scientists succeeded—sometimes with great difficulty—in making the case for new technology and approaches. Those approaches travelled globally: someone figured out how to immobilise large animals with drugs, another figured out how to put transistors on animal collars, and a tiger lay in a south Indian forest unable to move a muscle, eyes wide open. Tigers were immobilised and collared, just like the birds and bears. Nature was touched and managed, but the bureaucrats were still holding out.

Even as criticisms against the pugmark methodology mounted, the Project Tiger team continued to rely on it.²⁸ People I spoke to suggested this continued reliance was due to a combination of factors. Wildlife historian Raza Kazmi said that while bureaucratic egos and scepticism of science played a role, developing expertise in camera trapping was a genuine challenge, since many local collaborators had never even operated a camera. Dr Chandrima Home, who worked on the team right after the Sariska fiasco, agreed that training people and doing it country-wide was not easy.

And then came 2004. According to census reports, Sariska’s tiger population had been stable from 1993 to 2003, with 24-25 tigers in the reserve. The 2004 census had shown a drop to 16-18 tigers. It was all a fabrication.²⁹

Beyond the lack of scientific basis and validation issues in the pugmark method, there was another problem: pugmarks could be easily faked. The organisational structure meant that park managers oversaw data collection. As a result, tiger numbers often reflected their competence. Why would they accept that tigers had disappeared from under their binoculars?

Over the years, speculations were rife that tiger numbers were being inflated. Valmik Thapar, a noted tiger conservationist and Tiger Task Force member, frequently spoke about it and claimed that the government increased tiger numbers by 10 in 1997 to show progress.³⁰ In the same paper where he tested the accuracy of the pugmark method by surveying experts, Karanth also noted that the increase in tiger numbers was likely implausible and that, in certain reserves, there was not enough prey to support such a high tiger population.

Sariska proved all of these fears true. The local extinction of tigers made the national and international news. A few years later, it became the subject of a documentary narrated by David Attenborough. The pugmark system, already cracking under mounting criticism, fell apart completely after the tiger extinction in Sariska and was disavowed as unscientific.

The Tiger Task Force report suggested a change in methodology. The 2006 country-wide tiger count used a different methodology and reported 1,411 tigers in India. 452 fewer than in 1972. The number set off alarm bells across the nation. Aircel launched the ‘Save Our Tigers’ Campaign. More bad news followed as tigers went locally extinct in Panna Tiger Reserve as well. In 2010, NDTV joined Aircel in the campaign and aired 12-hour telethons featuring Bollywood star Amitabh Bachchan. The tigers had not yet been saved.

The four-yearly national tiger-counting exercise took on a new form. The first All India Tiger Estimate was conducted in 2006, and the new methodology incorporated many of the recommendations being made by experts for over a decade, including camera traps.³¹ Another key development that year was the amendment of the Wild Life (Protection) Act, 1972, to create a statutory body to oversee Project Tiger called the National Tiger Conservation Authority (NTCA). The NTCA and the Wildlife Institute of India (WII) took over the AITE's charge.

The exercise is divided into four phases. It is built on a double-sampling logic, where ground surveys of all beats are calibrated against intensive camera-trap blocks.

• Phase I involves a forest guard and assistant surveying every beat (about 15-16 km²; 15-20 km² in 2006) over 8-10 days, recording carnivore sign, prey on line transects, vegetation, human disturbance, and dung.
• Phase II involves compiling remotely sensed data matched to the Phase I grids, including forest cover, vegetation, terrain, roads, night lights, and human footprint.
• Phase III involves intensive camera-trapping at selected sites (in 2006, sites were stratified by high/medium/low/no tiger sign, and line transects also sat here until 2010).
• Finally, Phase IV involves intensive monitoring of source populations in tiger reserves: sign and photo monitoring until 2006 and annual camera trapping since then.

The essence of the field methodology has largely remained the same since 2006. However, the scale of and technology powering the endeavour has expanded and improved significantly. The analysis has changed the most. In 2010, WII brought in 58 trained biologists to run intensive surveys at 29 sites, with cameras placed on a 2x2 km grid (later nested within the fixed 100 km² national grid, which keeps cycles comparable). Occupancy models began correcting for imperfect detection. A new mobile monitoring system, M-STrIPES, let forest staff record tiger signs during everyday patrols rather than only once every four years, and better software also improved the mapping of habitat and wildlife corridors.

By 2014, the statistics behind the numbers became more rigorous. Spatially Explicit Capture-Recapture, which calculates density from the precise location of every camera and photograph, became the main landscape-wide method. In areas where cameras were impractical, researchers added testing of tiger DNA from scats as a backup. Groups like the Wildlife Conservation Society and Centre for Wildlife Studies ran their own site-level analyses, while all collaborators’ camera-trap data were pooled at WII.

By 2018, the assessment shifted decisively toward digital and automated tools. Paper forms increasingly gave way to the M-STrIPES mobile app, going fully digital by 2022. An AI tool called CaTRAT was introduced to automatically sort camera-trap photos by species, with trained staff checking the results. Camera coverage nearly tripled from 2014 to almost 27,000 locations (51 to 141 sites), and because the same 100 km² grid had been used consistently since 2006, researchers could run multi-season models tracking how tiger range expanded or shrank between cycles (colonisation and extinction, separate from the population estimate).³² The 2022 assessment estimated 3,682 tigers. The 2026 assessment is ongoing.

But experts warn that India is making the same mistakes, as tiger numbers on paper are rising too rapidly once again. They argue the methodology needs more work and the data must be publicly available so independent scientists can verify the data, methods and numbers. Finally, some argue that chasing highly specific tiger numbers is a futile task anyway since they are mostly unreliable. They suggest focusing on broader indicators, such as whether the areas where tigers are found are expanding or shrinking.³³​³⁴

In 1972, Choudhury argued that trip photography³⁵ could be used only in certain areas, not for the whole census, because the costs would be prohibitive. Fifty years later, the technology has come a long way and become affordable. And yet counting and saving tigers has never been just about technology.

The battle over using radiotelemetry was about something deeper. Older scientists worried that younger researchers were getting to know collars and computers better than the animals and land. Murie, who criticised the Craighead brothers for collaring bears, echoed this sentiment: ‘So many of the modern “wildlife management” scientists are spending so much of their time flying about in airplanes, counting animals, or marking them; they don’t get down and live with the animals and learn how they live.’ George Schaller also said, ‘Good fieldwork must be in the field, not at a computer terminal.’

Technology, however, did not automatically mean a disconnect with the land. Radio-collared animals still had to be located using traditional tracking skills, especially early on.³⁶ Slowly, the value of the research came to be recognised universally. The Craighead brothers, Hornocker, and Karanth are now all considered pioneers of the field. Their long-term research enhanced our understanding of tigers, mountain lions, and the ecosystems they inhabited.

So far, this story has been about solo heroes. However, none of them was alone. Local and indigenous people almost always helped them. Their knowledge played a vital role in all of the scientific knowledge gained, even if their names never made it into any publication.

Prem Bahadur Rai, the hunter who helped the Smithsonian team radio-collar tigers, was indispensable. Hemanta Mishra, the Nepalese scientist, wrote that despite his education and travel, he could never have radio-collared tigers without Rai. Similarly, Karanth’s early and most consistent team consisted of Jenu Kuruba tribesmen who used their traditional skills to radio-collar tigers.³⁷ The tribesmen followed tiger tracks minutely. Every leaf, every mark and the faintest sign of an animal spoke to them in ways that, even Karanth admits, were beyond his ability. A tiger had to be found for tranquilisation, and that work was done by Raju and other trackers on Karanth’s team.³⁸

Kazmi told me that while he agreed the tiger-counting methodology needed to become scientifically robust, tracking pugmarks was not entirely fruitless. Having accompanied many experienced adivasi trackers, Kazmi considers it an art that takes a lifetime to cultivate and cannot be taught in a week-long workshop. Rai also used pugmarks to locate tigers for radio-collaring in the Smithsonian project in Nepal.

In fact, Choudhury’s initial pitch for counting India’s tigers focused more on harnessing local and Adivasi knowledge than on pugmarks as infallible proof of tiger presence. He had grown up with Adivasi men who taught him the art of tracking, and he never took that for granted.³⁹ His ideas got mixed with the necessity for India to develop a cheap, local methodology, but at heart the idea was that of a ‘Cooperation Census’.

Ironically, traditional trackers like Rai used to be employed by hunters. They were largely ignored and forgotten later, as conservation did not adequately use their skills. Kazmi says most of this tracking knowledge is already lost and, without efforts to preserve it, will be completely gone in the next 10-15 years. On the opposite end, India also has a burgeoning citizen science movement that Karanth harnessed early on. He funnelled all the young nature enthusiasts coming to him into doing line transects. Some of these volunteers were so enamoured with wildlife that they changed careers.

Like Kazmi, others I spoke to fear we are losing the art of tracking and other forms of wildlife knowledge. A senior scientist told me that young scientists in training find it difficult to do fieldwork without their phones, and they now rely more on Google and AI chatbots.

Every generation thinks the next is getting softer. It is funny to think that individuals tranquilising, collaring, and tracking animals in difficult terrains were being accused of taking a shortcut. Karanth’s ‘bootcamps’ of volunteers were also notoriously difficult, and while he cultivated a group of committed wildlifers, many others did not last very long. Dr Dipankar Lahkar, a Senior Conservation Biologist at the Tiger Research and Conservation Division of the NGO Aaranyak, who has assisted in conducting the AITE in North-East India, said that volunteering for the AITE is quite tedious: hiking long distances with limited facilities, the same route, the same task every day, can take a toll.

Praveen Bhargav, who survived Karanth’s bootcamps and heads the NGO Wildlife First, has often said that the technology can be a force multiplier, only if we have boots on the ground. His only advice to young, budding naturalists is to hang out in the field. Kazmi agrees; he said imagine if the citizen scientists went out in their own communities to record and honour the lost art of tracking and living with wildlife.

It is difficult to give a straightforward answer to why India has succeeded in saving the tiger. Prickly questions about emerging technology in wildlife conservation remain far from settled, especially as advancements accelerate. We can't find refuge in a fantastical idea of pristine, untouched nature when humans have always been part of it, or in uncritically embracing every new gadget or technology without understanding the complexities of land, animals, and people. We may have left the tiger tracer and the pugmark census far behind, and the methodology will continue to evolve. But perhaps the answer lies in keeping the spirit of ‘Cooperation Census’ alive.