Two thousand, nine hundred and sixty-seven (2,967). It is the new magical number for India - the total tiger count after the fourth cycle of the National Tiger Assessment which reveals the country’s remarkable turnaround in the big cat's conservation.
But behind these glad tidings is an equally astounding feat, now being billed as the world’s largest biodiversity study. A bit of number crunching gives an idea.
Over 44,000 field staff of forest departments in 20 tiger-bearing states put in a whopping 5,93,882 man-days to generate data. When the first phase of the tiger assessment kicked off in January-February 2018, the frontline forest staff were in the field for 10 days capturing evidence. During the assessment, a staggering 381,400 sq km of forests were surveyed which included 522,966 km on foot. At least 317,958 habitat plots were sampled for vegetation and prey dung.
"It does not get any bigger than this, anywhere in the world. The sheer magnitude of the efforts put by various agencies of the country remains unmatched,” said Dr Anup Kumar Nayak, Member-Secretary, National Tiger Conservation Authority, the apex body on the big cats in the country.
So, what goes into the massive exercise that has caught the attention of the world? Months of planning and implementation, humongous manpower, back-breaking coverage of forest tracts and when the data is generated, new technology is used to filter the gigantic volumes of data. Since 2006 when it all began, a year after the Tiger Task Force was appointed by the then prime minister Manmohan Singh, the
pan-India exercise has only grown in size, scale, manpower and technology.
Behind it are the NTCA, its Tiger Cell, Wildlife Institute of India, the country’s top wildlife research agency which coordinates all the efforts with state forest departments, conservation NGOs and lots of top analytical minds to ensure that the final outcome stands the test of every scrutiny.
The entire tiger habitats of India, divided into five landscapes, come under the survey. Shivalik-Gangetic Plains, Central India and Eastern Ghats, Western Ghats, North Eastern Hills and Brahmaputra Flood Plains and the unique Sundarbans form the five landscapes where the survey is rolled out a year and a half before the final outcome is ready.
Work on the National Tiger Assessment 2018 started in September-October 2017 with the forging of a band of trainers at the WII, NTCA and forest departments. The trained officials then went back to their respective states and tiger reserves to train the field staff. Introducing technology and artificial intelligence (AI) into the exercise, M-STrIPES (Monitoring System for Tigers-Intensive Protection and Ecological Status), a GPS-based android mobile application system, was designed for field survey.
When Phase I of the survey kicked off, the frontline field staff used the application to upload the data into their mobile devices. The first phase is the key sign survey during which evidence of tigers, co-predators, prey density, vegetation, habitat quality and human impact are collected.
“Earlier, the forest staff used to find tiger sign in terms of, say, scats or pug-marks, and note down GPS coordinates on a piece of paper which was then punched into a computer. This process of generating sign evidence with GPS coordinates carried chances of mistakes. M-STrIPES simplifies it all by tracking kilometres covered and pictures of signs with geo-tagging. You can’t fudge it. All this is transmitted digitally to us for analysis. New improvements have been added this time which is now used for patrolling in 50 tiger reserves of the country,” explained Wildlife Institute of India scientist Dr YV Jhala, a top field biologist.
The NTCA Member Secretary elaborated how, during the sign survey, each team of two field staff perambulates five kilometres a day for three days. Then a 2 km line transect method is followed during which signs, prey density, habitat characteristics and interference of humans are collected. “This forms the basis for the next phase when camera traps are installed because sites, where tiger evidence is found, are recorded and range distribution is calculated,” he said.
The spatial coverage in the first phase is followed by remote sensing data of the landscapes, the habitat details and anthropogenic impacts in Phase-II, which takes into account forest size, topography, distance from core areas, human habitations, road network and a whole lot of details which are later used in
devising tiger occupancy and abundance.
Then comes Phase III in which camera traps are set up. Called Capture-Mark-Recapture, this stage includes individual capture of photographs of the animals to determine the density and abundance of large cats.
“Over the years, the methodology has not changed but the area under camera traps has proportionately changed. Earlier, we did not have that much money or resources, and camera traps were very expensive. Then we used film cameras which were very expensive, Now you get digital cameras which are cheaper. So, the number of cameras used has gone up though the area which is sampled remains the
same. Camera traps give you reliable information because they take you closer to the truth,” Dr Jhala pointed out.
From 9,735 camera locations in 2006, the number jumped to 26,838 locations in the 2018 Census. The camera traps (a pair) are installed in a specific 2 sq km grid size and placed in locations within 1 km of each other where movement of the carnivores is expected to be the highest based on the sign survey evidence. According to the tiger status survey report, the cameras were operated between 25 to 35 days at each site to generate at least 500 trap nights per 100 sq km.
How many photographs did the camera traps generate?
A whopping 3.48 crore which included tigers, leopards, other carnivores and a host of co-predators as well as prey species.
Filtering the huge volume of pictures is not humanly possible which is why a Camera Trap Data Repository and Analysis Tool (CaTRAT) was used to organize the individual pictures with geo-tags. To further narrow it down to species, for the first time, an artificial intelligence (AI)-based image processing tool developed by New Delhi-based Indraprastha Institute of Information Technology was used.
Using two different recognition programmes, it segregated photographs of tigers from leopards from the 3.5 crore photographs. “We generated 76,523 tiger photos and 51,337 leopard photos from the camera traps,” informed Dr Nayak.
From these, using specific models that identify the unique stripe patterns (for tigers) and spots (for leopards), individual animals were narrowed down. This process put the individual tiger photographs at 2,461. This number remains one of the benchmarks for the final tiger population estimation which is determined using the Spatially Explicit Capture Recapture (SECR) model.
“The SECR model uses covariates such as sign encounter rate, prey encounter rate, human impacts and remotely sensed data to arrive at the tiger estimation for individual tiger landscapes and the total number stood at 2,591,” the NTCA chief said.
The number of camera trapped tigers – 2,461 in total - is 83 per cent of the tiger population of 2,967 whereas what the SECR formula generates is 87 per cent of it. The rest 13 per cent is calculated using an extrapolation method from areas which are not camera trapped. “It is a process which is extremely scientific and uses various covariates as well as technology to arrive at an estimated tiger population,” Nayak asserted.
For the first time, tigers above one year have been brought under the enumeration. Earlier, only those above 1.5 years were estimated. The tiger assessment survey, apart from generating data about the large cats, also has in its repository a massive volume of photographs of other animals, ground evidence and signs which would be analysed later. Besides, DNA samples were also collected during the process but those would be discarded after generating the sequencing.
“National Geographic is slated to screen a special film on the survey on August 7. This is a massive effort considering the fact that filtering the photographs from camera traps alone would have taken us a few years,” said Dr Jhala who had 70 field biologists working full time with him for the one-and-a-half-year period.
Nayak revealed that over 400 to 500 researchers, apart from the Ministry of Forest and Environment, NTCA, WII and State Forest Departments put in a monumental coordinated effort for the survey.