Tiger census: Expert group questions methodology adopted

A day after tiger census declared a 30 per cent jump in big cat population, a wildlife expert group questioned the procedure India adopted for the estimation, saying the method used cannot yield "sufficiently refined results" to accurately measure changes in tiger numbers.
Wildlife Conservation Society (WCS) India, one of the NGO partners involved in the 2014 national tiger estimation effort in Karnataka, Wayanad-Kerala and Goa, said that the procedure is not the "best currently available methodology" for this task.
"We are of the view that the regression or calibration based double-sampling approach which was originally developed in 1938 and applied every four years since 2006 to Indian tiger surveys for estimating tiger numbers and distribution at landscape, regional and state levels, is not the best currently available methodology for this task.

"We do not believe this method can yield sufficiently refined results to accurately measure changes in tiger numbers at landscape or country-wide scales as is being attempted," said K Ullas Karanth, Director of Science, Asia WCS, and Director of Centre for Wildlife Studies (CWS), today.
The statement comes a day after the Environment Ministry released the latest census report saying the tiger population in the country has risen to 2,226 in 2014, a 30 per cent increase since the last count in 2010. The government has used the "refined methodology of double-sampling using camera traps" for the big cat population estimation.

In the double-sampling methodology, two sets of data are combined to estimate tiger numbers -- first by photographing tigers through cameras and then counting of paw-marks and scat (droppings).

Karanth said that alternative "superior" methods based on occupancy modeling approaches have already been demonstrated and published 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.
He said that any such distribution or occupancy surveys across country-wide scale conducted once in four years are only useful for answering "where are the tigers, rather than for estimating their numbers".