Sunday, June 20

Buffer-zone count makes Sunderbans tiger roar

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The Indian Sunderbans’ healthy increase in tiger count is mainly because of an unprecedented — almost unbelievable — more-than-fourfold jump in big cat number outside the tiger reserve area.

A detailed analysis of the tiger status report, 2018 — a quadrennial exercise — has revealed that the Indian Sunderbans logged a 16% growth in big cat population.

The range-wise break-up of data, gathered from camera traps placed across the mangroves in 2018, has shown that the South 24 Parganas forest division — the buffer area — is home to 22 tigers, 17 more than the number recorded during the same exercise in 2014. Compared with the 2014 exercise, it represents a 340% jump. During the same period, the jump in the reserve area was more modest, at 20%. Cameras placed in the tiger reserve area clicked 66 tigers, 11 more than the number in 2014.

According to the latest exercise, the Indian Sunderbans is now home to 88 tigers, with lower and upper limits of 86 and 90, respectively (the real population can be anywhere within the limits, with 88 the midpoint).

Foresters and scientists said the exercise this time was more accurate and the placement of cameras every 2sq km, instead of the usual 4sq km, has detected more tigers, some even from new areas.

Incomplete study in buffer area in 2014?

A senior forester said since about 600 cameras — 297 trap stations with two cameras at each station — scanned the mangroves during the latest exercise, the rate of captures also increased. During the exercise in 2014, the foresters could install only 200 pairs of cameras.

A source, however, provided a possible explanation for the huge rise. He said the exercise in 2014 had taken into account only five tigers — all from the Ramganga range — for the entire South 24 Parganas division. The exercise in another key zone of the buffer area — Raidighi — could not be undertaken at all. “This time, simultaneous exercise across the mangroves has thrown up a reliable estimate,” said a senior official.

Ravi Kant Sinha, the state’s chief wildlife warden, told TOI that 92 unique individual tigers were actually photo-captured across the entire Indian Sunderbans, spread over more than 4,000sq km in the latest exercise. “But four tigers were not included when the final data was compiled. While three of them were already photographed in the Bangladesh Sunderbans, inclusion of another tiger clicked in the Sajnekhali zone remained doubtful, as it was difficult to make out from the camera-trap image whether it was a cub or sub-adult,” he said, adding that each of the 88 tigers will get unique IDs.

According to him, the figure of 22 from forests outside the tiger reserve area once again shows that the population has remained stable throughout the mangroves.

The estimated tiger number in Sajnekhali and Basirhat ranges has also recorded a rise with 15 and 13, respectively. These two zones had recorded the presence of 13 and 10 big cats, respectively, when the cameras were placed in the forest five years ago.

Besides, two other key zones of the tiger reserve, National Park East and West, which are out of bounds for tourists, have together thrown up a figure of 38 tigers this time, six more than the 2014 figure.

On being asked about the significance of the population estimation of 88 being very close to the upper limit of 90, a scientist of Wildlife Institute of India, which is associated with the exercise, said: “This means that the estimation was quite precise. The tiger population in the Sunderbans remains quite stable, and it could increase if their prey base recovers. I believe cyclone Aila had a major impact on prey base, particularly wild pigs. If these recover, then tigers can increase.”

How will the unique tiger IDs work? An official said that codes in English lettering are assigned to big cats based on the landscape, not the state. “For example, the ID of a Sunderbans tiger will always start with the code SU. The unique IDs are being assigned to tigers only if their complete profile exists. A tiger, whose complete right- and left-side image is available with the foresters, will be eligible for a unique ID,” a forester said, adding that the move will help identify a tiger in case of natural death, poaching and migration from one habitat to another.


Source: Times of India

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