Answer from: Dr. Ullas Karanth, Director for Science-Asia, Wildlife Conservation Society (WCS):
The overall tiger numbers being reported by the Government, based on the Wildlife Institute of India’s surveys once in four years, are generated from a weak methodology and hence not very robust. The complicated, ‘double-sampling’ based regression model they use is a somewhat flawed and obsolete approach. Further, the quality of their estimates of tiger densities from individual sites that feed into this model vary. There are better ways of doing this, but they have spent Rs. 20 crores on two surveys so far and unfortunately seem poised to repeat the same again. This is a problem with the Ministry of Environment and Forests (MoEF) establishing a government monopoly on tiger monitoring and funding, with no periodic review and updating of methods in this fast growing field of quantitative ecology.
A global survey by WCS shows that 70% of surviving tigers are now concentrated within 6% of remaining habitat. My guess is that 80-90% of the wild tigers in India are concentrated within a few major protected areas (not just the ones designated as “Project Tiger Reserves”). The remaining forests have virtually no breeding tiger populations, primarily because their prey base has been hunted out. In the Malanad landscape from Goa to the southern tip of Karnataka, 90-95% of tigers are in protected areas. NTCA has recommended a set of robust protocols for monitoring tigers and prey, known as “Phase-IV section 3“, on their web site, although no State is implementing it rigorously. If this robust monitoring protocol is implemented sincerely in all protected areas, we will have sound knowledge of all viable tiger populations in the country, which is what we really need, rather than these country-wide numbers reported ritualistically once in four years.