The images are especially heartening in NSTR, which has been a conflict-ridden landscape owing to left-wing extremism for well over a decade.

Camera trap images of three tiger cubs and an adult female at the site of a cattle kill in the Nagarjunasagar-Srisailam Tiger Reserve (NSTR) in Andhra Pradesh have come as a boost to conservationists who hope to see recovery of the big cat population in an extensive area.

The photos, taken by cameras that are triggered off by sensors during the movement of tigers and other animals, show in sequence the scenes that biologists look for as evidence of breeding tigers - a mother and three cubs at a kill.

Preliminary analysis of the images taken at night on July 6 and 7 indicate that the cubs are four or five months old. The site is about a kilometre from the office of the Field Director of the NSTR.

The “India Tiger Estimate 2010” of the Ministry of Environment and Forests records an overall decrease in the tiger population in reserves of Andhra Pradesh among protected areas of Central India and the Eastern Ghats. Madhya Pradesh is another State with a recorded decline, while others in the region are either stable or have recorded an increase.

Among the key conservation points that the India Tiger Estimate report highlights is the need to secure corridors between source sites, to improve the prospects for tiger persistence outside reserves and sanctuaries.

The 3,568 sq km Nagarjunasagar-Srisailam Tiger Reserve, located in the Nallamalai Hills of the Eastern Ghats, is the largest among the 40 tiger reserves in the country. It is adjacent the large Gundla-Brahmeswara Wildlife Sanctuary. It is also home to the historic Srisailam Shiva temple.

A note sent by the Nagarjunasagar-Srisailam Tiger Reserve points out that though the area came under Project Tiger in 1982-83, the NSTR has been a conflict-ridden landscape owing to left-wing extremism for well over a decade. The MoEF found it a challenge to protect it. With left-wing extremist activities in the area waning in recent times, concerted efforts by the Centre and the State resulted in the gradual revival of the ecosystem. The local management team led by Field Director Ajay Naik came up with an innovative strategy, to deploy the local Chenchu tribes for protection duties. As many as 250 young Chenchus have been engaged by the Forest Department to protect forests and wildlife.

Union Minister for Environment and Forests Jairam Ramesh said, "To me the involvement of Chenchus in tiger protection is very significant and is a model we want to replicate elsewhere. The habitat is tough but the field director and his staff are doing an outstanding job."

The outcome has been an improvement in the spatial occupancy of tigers in the reserve. The recent estimation by the NTCA and the Wildlife Institute of India in 2010 indicated a population of 60 tigers (lower limit 53, upper limit 66). The management is using as many as 30 pairs of camera traps to monitor tiger presence, besides collection of other evidence in the field during day-to-day patrolling. The reported presence of around 20 tiger cubs in the reserve is an indication of habitat recovery.

Research scientists have pointed to the benefits of carrying out camera trapping in all reserves on a continuous basis, as this would provide a more accurate picture of the national tiger population. Camera trap images also help identify individual tigers, since the stripe markings are unique for the big cat.