India Counts Its Tigers With Camera Traps at 32,588 Locations and Reports a Range of 3,167 to 3,925, While Its 891 Lions Are Counted by More Than 3,000 People Watching for 24 Hours

India does not count its tigers one by one. In 2022 forest staff walked 641,449 km of trails and survey lines, camera traps went up at 32,588 locations and photographed 3,080 individual tigers by their stripes, and a statistical model then estimated that the country held 3,682 tigers older than a year, within a range of 3,167 to 3,925.

Gujarat counts its Asiatic lions another way. In May 2025 more than 3,000 forest staff and volunteers watched assigned patches of land across 35,000 sq km, each patch for 24 hours, and the state reported 891 lions as a single figure.

Plaster casts of a left hind paw

A pugmark is a tiger’s paw print, and for about three decades India counted tigers by collecting them. Down To Earth traced the pugmark census to 1966 and a man named S R Choudhury. In an article of 15 March 2005 the magazine described the routine: thousands of people searched forests for tracks for a week or two each year, made plaster casts of the left hind paw, and compared the casts to tell one tiger from another.

In 2003 K. Ullas Karanth, James Nichols and seven co-authors published a critique in the journal Animal Conservation. They set out three goals for monitoring a species, in rising order of difficulty: mapping where it lives, tracking whether it is becoming more or less common, and estimating its absolute numbers. Their abstract concludes that the pugmark census skips the first two and fails at the third. Down To Earth reported one of their objections, that tigers do not form pair bonds and so the same animal can turn up in several counting areas. Rajesh Gopal, then director of Project Tiger, defended the method to the magazine as cost-effective.

The reset after Sariska

The National Tiger Conservation Authority’s 2022 report dates the turn to 2005, when the local extinction of tigers in Sariska Tiger Reserve came to light. The government then moved to managing tigers region by region, with strict monitoring, and the authority’s 2011 booklet says a national estimate has been made every four years since 2006. The first returned 1,411 tigers, with a range of 1,165 to 1,657.

That estimate ran in three phases: beat-level field data collected by trained forest staff, satellite analysis of habitat, and camera trapping, which the booklet calls the primary method of the third phase. It says the same methods were used in 2006 and 2010. In 2010 about 800 camera traps covered roughly 10,500 sq km and photographed 550 individual tigers. Forest staff sampled 29,772 beats and walked about 625,000 km, at a total cost of Rs 9.1 crore (Rs 91 million). The 2010 estimate was 1,706.

Karanth proposed the photographic method in 1995, according to the abstract of his 1998 paper with Nichols, and he disputes how the national exercise uses it. He told Down To Earth in July 2023 that the 2006 figure of about 1,400 came from a reset under the new method, and that the authority releases summary reports and not raw data. Mongabay India reported on 4 August 2023 that Karanth says the camera-trap surveys, run in smaller areas, violate basic statistical assumptions, and that data from the surveys since 2006 have not been shared with independent scientists.

How capture and recapture works

Capture-recapture estimates how many animals exist from how often the animals you catch turn out to be ones you caught before. A tiger’s stripes work as a permanent mark, so a photograph counts as a capture and a later photograph of the same animal is a recapture.

Here is a small example, with invented numbers. Cameras in one block photograph 40 different tigers in the first fortnight. In the second fortnight they photograph 30 tigers, and 20 of those are among the 40 already seen. Two thirds of the second batch were already known, so the 40 known tigers are about two thirds of the population, which puts the total near 60. Course notes from Montana State University give the same sum for two sampling occasions, called the Lincoln-Petersen estimator: the number caught the first time multiplied by the number caught the second time, divided by the number caught both times. Here that is 40 times 30, divided by 20.

The notes list the conditions. The population must be closed, with no births, deaths, arrivals or departures during the study. Marks must not be lost or misread. Every animal must be equally likely to be caught, which the notes say almost always has to be relaxed. Real surveys therefore use more than two sessions and models that allow for differences in capture chances. The authority’s report uses spatially explicit capture-recapture, which in its words adds the location of each photo-capture to give clearer and more precise density estimates.

Karanth and Nichols tested the approach in four Indian habitats and published it in Ecology in 1998. They estimated the chance of photographing a tiger that was present at 0.75 to 1.00, and the density of tigers older than a year at 4.1 to 16.8 per 100 sq km. Density generally rose with prey density, except at a site affected by poaching. Their abstract says earlier track-based total counts had proved unreliable.

Three phases and a calibration

Phase I of the 2022 round belonged to the forest beat, the patch a single guard patrols, which averages about 15 sq km. Staff in 20 states recorded carnivore signs, counted deer and other prey along survey lines, and logged vegetation, human disturbance and dung, entering the results on a mobile app called M-STrIPES. A beat took at most 10 days for two people. The report counts 641,102 man-days of work in all and says the authors believe it is the largest wildlife survey effort anywhere.

Phase II is done at the Wildlife Institute of India in Dehradun, from satellite and map data: forest cover, vegetation greenness, forest patch size, elevation, distance to roads and night-light intensity, among others.

Phase III is the camera trapping. Cameras went into 2 sq km cells inside the fixed grid of 100 sq km squares that India has used since 2006, with at least one pair in each cell, at least about 1 km apart, in blocks of at least 200 sq km, for 25 to 35 days. The effort averaged more than 1,500 trap-nights per 100 sq km. The cameras took 47,081,881 photographs, 97,399 of them of tigers. An artificial intelligence tool built with the Indraprastha Institute of Information Technology in Delhi sorted pictures by species, ExtractCompare software proposed matches between stripe patterns, and people made the final visual comparison. Where cameras could not go, because of logistics or insurgency, and tigers were few, scat was collected for DNA analysis.

The report calls the design a derivation of double sampling. Raw counts and indices collected across the whole survey area are calibrated against absolute density measured in limited sample areas, and the estimate is extrapolated to places where tigers were found by sign but not photographed, using the relationship between tiger density and the covariates. Sign surveys cover the whole forest, camera trapping measures density directly where the cameras stood, and the model links the two.

Why the 2022 answer came in two steps

The summary report released in April 2023 gave 3,080 individually photographed tigers and a minimum population estimate of 3,167. It said the spatial modelling was still under way at the Wildlife Institute and that the minimum had also been worked out with the traditional capture-mark-recapture method. Mongabay India described the 3,167 figure as based only on camera-trapped areas.

On 29 July 2023, Global Tiger Day, the environment ministry said further analysis by the institute, covering both camera-trapped areas and areas with tigers but no cameras, put the upper limit at 3,925 and the average at 3,682, with annual growth of 6.1 percent, All India Radio reported. On 1 August 2024 Minister of State Kirti Vardhan Singh told the Rajya Sabha that the number had risen to 3,682, with a range of 3,167 to 3,925, and that growth is about 6 percent a year when consistently sampled areas are compared, Down To Earth reported.

Earlier rounds came with ranges too. The 2022 report gives 2,967 for 2018 with a range of 2,603 to 3,346 and says the bracketed figures are one standard error limits of the mean, a narrower band than the 95 percent intervals many journals use. The sources reviewed give no statement of what kind of interval the 2022 range is, and it overlaps the 2018 range between 3,167 and 3,346. How the regional numbers differ is covered in an earlier tuput article on the headline figure.

Indian agencies publish error margins elsewhere as well. The weather department’s release of 15 May 2026 put the monsoon’s onset over Kerala on 26 May with a model error of plus or minus four days.

Lions are counted by eye

Gujarat’s Forest Department counted its Asiatic lions in 2015, 2020 and 2025. The 2015 count, according to India’s Endangered, watched waterholes for 24 hours with roughly 1,400 to 2,000 people over two to three days. It gave 523.

The next figure, 674 in June 2020, did not come from a full census. India’s Endangered reported that the pandemic lockdown replaced it with Poonam Avalokan, the full-moon observation that field staff already did monthly, over 5 and 6 June. A limited staff covered 10 districts and 13 forest divisions, and teams kept moving instead of staying at waterholes, which the article says leaves room for lions to be counted twice or missed. A month before the planned count, the same outlet reported on 2 April 2020, Gujarat dropped a proposal to use 8,000 to 10,000 camera traps and the expertise of the Wildlife Institute of India. Shyamal Tikedar, then the state’s principal chief conservator for wildlife, said lions, unlike tigers, are not elusive, so direct sighting should be enough.

The 2025 count ran from 10 to 13 May in two phases, a preliminary count on 10 and 11 May and a final count on 12 and 13 May, over about 35,000 sq km in 58 talukas (sub-districts) of 11 districts. The Forest Department’s release, carried by PTI on 21 April 2025, calls the method direct beat verification and says it gives near-complete accuracy. Volunteers received forms and maps of their areas and recorded sightings with time, direction of movement, sex, age, identifying marks and GPS location. Some lions wore radio collars, and entries went through a phone app, e-GujForest.

Mongabay India, on 7 January 2026, added the structure. The department divided 13 administrative divisions into 735 sampling units. Each had an enumerator, who was a beat guard or forester, two assistants and a volunteer, who recorded sightings over 24 hours with photographs and forms noting sex, markings and whether cubs were present. Sightings were cross-checked at regional and zonal levels, and AI was used to remove duplicates. Mongabay calls this the minimal total count method.

The result was 891, up from 674. Down To Earth reported on 21 May 2025 that 384 were in Gir National Park and Wildlife Sanctuary and 507 outside it, a split given by the Principal Chief Conservator of Forests, Jaipal Singh. Mongabay’s later piece gives 394 in Gir and adjoining areas and 497 in nine satellite populations.

Critics question the method. Ravi Chellam, a lion expert, told Mongabay that it is prone to human error, that lions lack the distinctive body markings that make camera-trap identification work for tigers, and that most wildlife estimates carry a range while this one yields a single number. Y V Jhala of the Wildlife Institute of India said in 2020 that a method he called 100 years old could badly undercount or overcount lions that range over up to 700 sq km. Researchers have proposed capture-recapture and identification by whisker spot patterns. The department says its method is accurate, and the sources reviewed here contain no independent test of that claim.

The sixth tiger round

The Tribune reported on 26 August 2025 that the sixth All India Tiger Estimation would assess 58 tiger reserves, up from 51 in the fifth, that forest staff were being trained, and that camera-trap data would be analysed with artificial intelligence. Indian Masterminds reported that Karnataka’s Phase I field survey, with carnivore sign surveys and line transects for deer and other prey, began in January 2026 across all 54 of its forest divisions.