Rise in tiger count: Experts skeptical of census methodology

The survey methodology assumes that there is a strong relationship between tiger signs and the real number of tigers, but experts contend that it is not the case

Bandhavgarh National Park along with Guru Ghasidas (Sanjay) National Park has 141 tigers. Last year, in the midst of the pandemic the park welcomed six tiger cubs Photo: iStock

Following the release of the Tiger Census 2018 report on Tuesday (July 28), many tiger experts in the country have expressed their concerns over the Centre’s claim that the tiger population had gone up.

As per the report, the tiger population has increased to 2,967 in 2018 from 2,226 in 2014. The Centre claimed that it had met its deadline of Petersburg Declaration, signed in 2010, on doubling the tiger population, two years ahead of the stipulated time of 2022.

But the country’s well-known tiger conservation experts said the methodology adopted by the government in tiger census had many flaws.

“Spending a lot of money and placing cameras without capture-recapture protocols is of no use. The longer you keep the cameras, the more will be the tiger count,” said noted tiger expert K. Ullas Karanth, the director of Centre for Wildlife Studies, Bengaluru. “Are the losses of tigers being estimated using any scientific methods,” he asked.


‘Open-mindedness is lacking’

There are too many flaws and experts have criticised these multiple times. Photos obtained without proper field and statistical protocols are not useful, Karanth added.

Besides camera traps, the census uses a methodology called ‘index of tiger abundance’, which is derived from the number of tiger signs. The survey methodology assumes that there is a strong relationship between these signs and the real number of tigers. But experts contend that it is not the case.

“Peer-reviewed science has discredited this methodology and these results are unreliable. Alternative approaches have been provided several times, and published, including in a comprehensive Springer Monograph, titled ‘Methods for Monitoring Tiger and Prey populations’ in 2017, with 31 authors, edited by Jim Nichols and myself. What is lacking is an open mind to explore,” said Karanth.

These figures were released a few months ago and are being rehashed, he added.

Problem of overdispersion 

“In our country, which has enough habitat to support at least 10,000 tigers, government is now ‘celebrating’ the increase of tiger numbers from 2,000 in 1970 to 3000, after 50 years of expensive efforts. Worse still, it now believes only we can only have 3,500 tigers. If this is all we can do what is there to celebrate? Why are we spending so much money with such fanfare?” Karanth wrote in his blog.

We certainly will have space for more tigers, if the animals and their preys are protected over a wider area. Hunting by local people is the main reason for the decline of preys, he said.

“This tiger report indicates that the problem of overdispersion not only persists from earlier reports, but it is further accentuated now,” said Arjun M. Gopalaswamy, wildlife and statistical ecologist, Wildlife Conservation Society, USA.

In simple terms, overdispersion means high variability. For example, India has reported a doubling of the number of tigers (from 1,411 in 2006 to 2,967 in 2018). Overdispersion in this context is that there is a higher uncertainty over these numbers than those claimed in the report.

“Known ecological, methodological oddities remain and a few new ones have emerged. A thorough reanalysis is necessary, prior to policymaking,” said Gopalaswamy.

A time-tested model

Differing from independent experts, K. Sankar, director, Salim Ali Centre for Ornithology and Natural History (SACON), Coimbatore, and who was earlier a faculty member in Wildlife Institute of India (WII), which carries tiger census, said the methodology used in the census was time-tested.

“We tested this methodology in Kanha tiger reserve many years ago. After that, this is used across the country for the census. The methodology is also used by other countries such as Nepal and Bhutan. Science keeps evolving. If independent experts have a better methodology or if they give any ideas to improve the current method, they are always welcomed,” he said.

The data is collected by forest guards. If we ask only scientists and researchers do the census, it is impossible to cover all the areas. Though the census is carried out once in four years, field staff collect the data throughout the year and it has become part and parcel of regular monitoring, he said.

“We have good equipment like cameras and software. If there are any doubts in the data, the researchers will get in touch with the field staff and clear it. Sometimes, the staff mark the latitude and longitude wrongly. The data will be cleaned in WII. So the manual error gets largely decreased,” said Sankar.

‘Why resettle people?’

The report also suggests that the people, who are residing in many tiger reserves, be resettled.

“The increase in the tiger numbers shows that the people in the tiger reserves have learnt to coexist with the tigers. There is no connection between the tiger numbers and the people living in these reserves. When the tiger numbers are going up, why are people seen as problems? Why should be they resettled,” asked Nitin D. Rai, researcher, Ashoka Trust for Research in Ecology and the Environment.

The National Tiger Conservation Authority (NTCA) published two kinds of reports. One, the status of tiger numbers and the economic value of tiger reserves. The second shows how these tiger reserves are earning profits through tourism and calls for more investment from corporates.

“But unfortunately, the local communities in these reserves are not valued. They are not allowed to collect small forest produces or to take up agriculture, etc. When they are left out, the economic valuation of the reserves becomes meaningless” said Rai.