In a bid to minimise error on estimation of tiger population, the National Tiger Conservation Authority (NTCA) has made coverage of entire tiger reserve a must for the next phase of big cat population estimation.
Number of Indian and foreign tiger scientists have raised doubts over the latest tiger estimation figure of 1,706 raising question marks over the methodology adopted. In most tiger reserves only the core-critical area was surveyed for tiger estimation.
Taking the criticism into account, the NTCA has updated the methodology and prescribed coverage of entire tiger reserves either by camera traps to take pictures of the cats or through DNA testing of the fecal.
"If the survey area is very large, tiger population size can be obtained by sampling a minimum block of 400 square kilometers at a time," the new tiger estimation guidelines circulated to the state forest departments governments said.
The guidelines also say that if deployment of camera traps in an entire reserve or parts of it is not feasible for any reason, fecal DNA samples may be collected over the entire tiger reserve for capture-recapture analysis, methodology to cross check DNA findings with camera trap pictures.
To minimise the errors arising of keeping the camera traps open for a longer duration, the authority has prescribed the duration for which the camera trap should be opened and closed.
"Keeping the camera open can led to higher estimation of tigers," said K Ullas Karanth, director of Bangalore-based Centre for Wildlife Studies, who had questioned the methodology of earlier tiger estimation.
A key to estimate the tiger population correctly is prey population. NTCA has stipulated new software called DISTANCE to estimate prey density.