India is currently thought to hold 50% of wild tigers. These tiger populations, however, are distributed over vast, fragmented forest blocks that cover 100,000–200,000 km2. Of this habitat only 25% is in protected Tiger Reserves. Consequently, monitoring tiger populations has been a challenge. After the failure of the traditional pug-mark census practice based on total track counts was recognized by the Government in 2005, India's National Tiger Conservation Authority (NTCA) made efforts to develop newer methodologies to monitor tiger populations more reliably.
A global biogeographical analysis led by Wildlife Conservation Society (WCS) scientists (Walston et al., 2010, PLoS Biol, 8(9), e1000485) showed that about 70% of wild tigers, including cubs and transients, are now concentrated in only 6% of the remaining 1.1 million km2 habitat, thus highlighting the need for intensive annual monitoring of these source populations. The NTCA has been working with WCS scientist Ullas Karanth to refine monitoring methods for key tiger source populations, based on research and experience gained from his long-term efforts in the state of Karnataka. In the Malenad–Mysore landscape in Karnataka, working in collaboration with the State Forest Department, Karanth and his team have been monitoring five tiger source populations in 4,000 km2 for over a decade, using advanced photographic capture–recapture methods to generate reliable estimates of tiger population size and density, and survival, recruitment and dispersal rates (Karanth et al., 2011, Science, 332–791). These data show that tiger densities are high (10–15 tigers per 100 km2) in well-established reserves such as Nagarahole and Bandipur, and are increasing (3–6 tigers per 100 km2) in two other reserves in response to recent conservation measures.
Refined tiger monitoring protocols under Phase IV of the national tiger estimation announced recently by NTCA (http://projecttiger.nic.in/whtsnew/Protocol_Phase_IV_Monitoring_r.pdf) specify rigorous new monitoring standards, such as a minimum sampling area >400 km2, a trapping intensity of 1,000 traps per 100 km2 and a closure period of 45–60 days. These are also linked to a national database of tiger camera-trap photographs being set up in collaboration with scientific institutions. It is expected that these refinements to the monitoring protocols will lead eventually to rigorous tracking of tiger numbers in all key source populations in India, thus enabling authorities to manage wild tiger populations more effectively.
