All India Tiger Estimation: Count may rise but accuracy of methodology under doubt
New Delhi India’s latest tiger count, to be released on Monday, which is also International Tiger Day, will likely show an increase in numbers of the big cat, National Tiger Conservation Authority (NTCA) and Wildlife Institute of India (WII) officials said, although some scientists and statisticians say questions around the accuracy of the methodology used -- the same as in the previous count in 2014 -- still persist.
The All India Tiger Estimation results for 2018 will be released on Monday by Prime Minister Narendra Modi, along with a report evaluating the effectiveness of tiger reserves.
There is an appreciable rise in tiger numbers with the same states as 2014 (Karnataka, Madhya Pradesh, Uttarakhand, and Tamil Nadu) taking top positions, according to officials at WII, which collaborates with the NTCA on tiger estimation. “The year there has been an increase in camera coverage of tigers. It is a good thing,” said one of these officials who asked not to be named.
The last tiger census in 2014 estimated that there are 2,226 tigers in India. Karnataka led with 406; Madhya Pradesh had 308; Uttarakhand, 340; and Tamil Nadu had 229.
T Balachandra, conservator of forests and field director, Project Tiger, Bandipur (Karnataka) said: “We are expecting our tiger numbers to be at least 450 this time. Bandipur has at least 135, Nagarhole has about 100. We have almost reached a spillover point. To avoid conflict, we have improved prey base and maintained grasslands.”
That’s almost a 11% increase in Karnataka.
India’s tiger count methodology has been questioned by some scientists who have issues with the so-called double sampling methodology which India uses to estimate tiger numbers. India abandoned the pug mark census method in 2004 after this failed to detect the complete extinction of tigers in Sariska tiger reserve. The new method being used involves ground surveys of all tiger bearing forests, estimating prey abundance, understanding habitat characteristics, mapping other tiger signs, and camera trap pictures of tigers.
Veteran wildlife biologist, K Ullas Karanth said as early as 2015 that the statistical model used may be giving misleading results. Between 2006 and 2010, tiger habitat in India shrank by 22% but tiger numbers rose by 16%, he pointed out. The 2014 data showed another 30% jump in the next four years. “Estimated leaps of over 100% in just four years, reported for some states, are also not plausible,” Karanth wrote in an article in The Guardian. He added that the Wildlife Conservation Society, Oxford University, and the Indian Statistical Institute tried to evaluate the government’s models with little success.
In the double sampling method, counts of tiger tracks are correlated with actual tigers photographed in small areas to provide region wide estimates.
Karanth along with other scientists from the Indian Statistical Institute, Wildlife Conservation Society, Tata Institute of Fundamental Research and University of Oslo have raised the concerns with the methodology in a paper yet to be published where they have questioned whether science has influenced conservation policy in India.
Anup Nayak, member secretary, NTCA dismissed these objections. “This time we have made some minor modifications. The grid size has come down but the principle is the same. Our numbers are absolutely accurate. They cannot be challenged.”
Arjun Gopalaswamy from the Indian Statistical Institute and lead author of the to-be-published 2019 study on flaws in India’s tiger estimation methods said : “As part of NTCA protocols, all tiger reserves were meant to be conducting camera trap surveys of tigers annually. These surveys should provide the answers we are looking for from the stand point of tigers—are tiger population sizes increasing or decreasing? What are their survival rates? How many tigers are being recruited into the population? But we are yet to see these results from individual reserves.”