The number of tigers at the reserve for the big cats in Valmikinagar could be double since the last census conducted three years ago.

According to the annual tiger census conducted over the past six months, the number of adult tigers at Valmiki Tiger Reserve (VTR) could be between 18 and 20. The final report is yet to be submitted. Apart from the adult tigers, three cubs have also settled at the reserve spread over 901sqkm in Bagaha block of West Champaran.

According to the camera-trapping census used in 2010, eight tigers had been detected in the 440sqkm core area of the reserve. Officials at the reserve said the increase in the number of tigers was a result of a favourable habitat for the big cats. “Breeding could not have been so frequent and successful that the number of tigers would increase by over double during the past three years. Rather, there must have been a reverse migration trend among tigers between Chitwan National Park in Nepal and the VTR,” said a senior officer of the environment and forest department.

He added: “Earlier, tigers used to migrate from the VTR to the Chitwan. However, the increase in grassy land and herbivores at our reserve over the past three years must have attracted the tigers.”

The census work mandated by National Tiger Conservation Authority (NTCA) started on January 15. It used 120 cameras installed in pairs across the park.

“Though the tigers seem to have settled almost all across the reserve, their density is higher in Madanpura and Manguraha ranges,” said the forest department official.

Sources said the number of tigers in the Manguraha range increased significantly after the Supreme Court stopped stone mining there in 2004. Tigers apart, golden cats and leopards, were also spotted for the first time at the VTR during the census.

Apart from the VTR, the tiger census work was done simultaneously at other adjoining tiger reserves in Uttar Pradesh, Uttarakhand and Nepal, with the help of the India chapter of the World Wildlife Fund.

The international organisation is preparing a comprehensive databank of tigers in Terai Arc region comprising protected eco-systems across the India-Nepal border. The region has a number of wildlife reserves and sanctuaries — Nepal National Park, Parsa, Chitwan National Park and Bardia National Park in Nepal; VTR in Bihar; Sohagi Burwa Wildlife Sanctuary and Dudhwa National Park in Uttar Pradesh; and Corbett Tiger Reserve in Uttarakhand. WWF, India, is at present preparing the final report of the tiger census at the VTR. Jimmy Borah, the national coordinator for Tiger Programme of WWF, India, said: “The field work for the tiger census has been completed at all the reserves in India. It is likely to take another month to complete the work in Nepal. We intend to hand over the final report for the VTR to the state forest department by the first week of August.”

Forest department officials said they plan to release the report on August 9 on the occasion of Kranti Divas. “We are also going to send the findings of the tiger census work to the NTCA in their prescribed format along with the photographs,” said the forest department official.

The VTR is 289km north of Patna in the Terai region of the Himalayas extending to Royal Chitwan National Park and Parsa Wildlife Sanctuary of Nepal on its north and Uttar Pradesh at its west.