An exercise to estimate the number of tigers in the Sunderbans started on Thursday.

Installing trap cameras across the mangrove delta marked the beginning of the census.

In total, 1,444 cameras will be placed in 722 grids. Each 2sqkm grid will have a pair of cameras placed in opposite directions.

The Sunderbans are spread across 10,000sqkm, a little above 4,000sqkm in India.

The Indian Sunderbans is split between the Sundarban Tiger Reserve (STR) and the South 24-Parganas forestdivision.

“The cameras will be placed between November 21 and 26 and retrieved between January 6 and 12,” said Nisha Gowami, the divisional forest officer of South 24-Parganas forest division.

Forest officials said the images captured by the cameras would then be analysed to estimate a number. Ocular estimation and other tools will be collated with the images.

The estimation excludes cubs. Only tigers more than a year old are included in the count.

The annual exercise is conducted by the forest departments of the states that have tigers in the wild.

The national tiger census, a quadrennial exercise, is conducted by the National Tiger Conservation Authority, which functions under the Union government.

The national estimate is a much bigger and more detailed exercise that studies multiple factors, like prey base and human interference — beyond just the tiger number.

The 2018 national count had pegged the number of tigers in India and the Sunderbans at 3,682 and 101,respectively.

This is the first time the cameras will be placed simultaneously in the STR and the South 24-Parganas forest division. Usually, the cameras are placed in a phased manner.

Some 320 cameras are being placed South 24-Parganas and around 1,100 in STR, officials said.

The STR is made of the Sunderbans National Park (East and West), which is the core area, and the Sajnekhali Wildlife Sanctuary and the Basirhat Range, which form the buffer zones. The South 24-Parganas comprise three ranges, Matla, Ramganga and Raidighi.

“We are covering more than 95 per cent of the forest area. The forests of STR have tigers almost everywhere. But in South 24-Parganas, the exercise can throw up some new tiger habitat,” a forest official said.