BENGALURU: A day after official figures showed a 30 per cent increase in India’s tiger population since 2010, tiger experts have questioned the ‘double-sampling’ approach used for the survey by National Tiger Conservation Authority (NTCA).
According to the experts, the double-sampling approach, used since 2006 in tiger surveys, is “not the best currently available methodology for this task”.
In this method, two sets of data — camera traps and pug marks and scats — are combined to get an estimate of the number of tigers in a particular area.
Outlining his overall assessment of the NTCA report ‘Status of Tigers in India, 2014,’ Dr K Ullas Karanth, Director for Science-Asia, Wildlife Conservation Society (WCS), said, “We do not believe this regression /calibration-based double sampling method can yield sufficiently refined results to accurately measure changes in tiger numbers at landscape or country-wide scales as is being attempted.”
He said they have demonstrated and published alternative superior methods based on occupancy modelling approaches, which have evolved strongly after the year 2000.
“We believe that these alternatives are more cost-effective and should be implemented instead of the currently-used double-sampling approach,” he said.
Dr Karanth, however, commended states like Karnataka, Madhya Pradesh, Maharashtra, Uttarakhand and Assam, saying they have used central funds effectively, and put in substantial effort to improve patrolling and protection, promote voluntary village relocations and expand tiger reserves or add new ones.
Local NGOs, including WCS, have contributed to prevent harmful impacts on tiger habitats. As a consequence, the status of tigers has generally improved as concluded by the preliminary report. However, the degree and extent of this population recovery requires closer examination, he said.
Dr Karanth said over 90 per cent of all tigers in the country come from 30 to 40 major source populations, and their rigorous annual monitoring using newer protocols can yield more accurate tiger numbers. “We welcome the fact that NTCA is moving in this direction,” he said.