There was much rejoicing when global tiger numbers rose from 3,200 in 2010 to 3,890 in 2014. However, was it a case of tiger numbers having gone up owing to improved conservation measures or was it the result of better surveys, such as deployment of more camera traps and changes in analytical methods? The question has been raised following a study published in the journal Conservation Letters , in its September 9 issue.
Scientists from Panthera, Nature Conservation Foundation (NCF-India), Colorado State University, and the Wildlife Conservation Trust studied the camera trapping methods used in India and Nepal in consecutive surveys. They found that in India, the biggest host nation, increase in tiger numbers corresponded with a 538% increase in camera traps deployed, resulting in a 144% increase in tigers photographed. Besides, the 2014 surveys were conducted in 32 additional locations, which in itself could have contributed to the rise in numbers.
In camera trapping, one of the methods used to estimate numbers every four years, wild tigers are photographed using remotely-activated cameras.
While their unique stripe patterns help identify individuals, information including the number of cameras used and locations surveyed is also crucial to arrive at estimates, for results from small areas are extrapolated to larger protected areas to arrive at countrywide estimates. Factoring in tiger behaviour and territoriality, robust estimates can be obtained only if camera-trapping is completed in a single location within 45-60 days. However, this was violated across 29 locations in the 2014 census.
The census used new sophisticated methodology which could hardly be compared with earlier estimates as different analytical methods, which were not calibrated for comparison, were used, says Abishek Harihar, scientist working with Panthera and NCF-India. “It is impossible to infer countrywide or global increase in tiger populations from this,” he says.
No independent scrutiny
Biologist Ullas Karanth, who raised similar questions in the past, says, “The study reinforces how sloppy the survey methods and results are, which some of us had statistically demonstrated earlier. It is a black box, with the MOEFCC not open to any independent scientific verification, despite the tax payer having spent over ₹40-50 crore in the last decade.”
However, the National Tiger Conservation Authority, which conducts the countrywide tiger estimation exercise, said this was nothing but a “disinformation campaign... aimed at casting doubt on the All India Tiger Estimation.” In an e-mail to The Hindu , Vibhav Mathur, Assistant Inspector General, NTCA, said the methods evolved by Project Tiger and the Wildlife Institute of India after a rigorous pilot initiative, involved composite double-sampling, assessment of tigers and co-predators, their prey and habitat. New areas surveyed were explicitly mentioned in the final result.
“The analysis/inference is done only from [photo] captures obtained within a specific period,” he said, buttressing his argument that there was no violation of the time-bound study that such analyses need.
