The Sundarban mangrove forests, a UNESCO World Heritage Site spanning India and Bangladesh, are home to 182 tigers, a first joint population estimation exercise of the two nations has revealed.

While India has 76 tigers, the Bangladesh Sundarbans are home to 106 tigers. The estimation was carried out by National Tiger Conservation Authority and the Bangladesh Forest Department.

AT A GLANCE Tigers are thriving in Sundarbans , finds joint study. India has 76 tigers while Bangladesh has 106 More than human interference, it is climate change that poses potent threat to them.

​Sundarban is the only exclusive mangrove habitat where tiger exists giving it the status of Level I Tiger Conservation Unit. These tigers differ morphologically from the mainland tigers, and are also genetically one of the most divergent groups among Royal Bengal tigers.

Both agencies used the modern camera trapping methodology to count tigers in the marshy mangrove forests, which is a tough terrain to cover. Back in 2004, the last census of tigers in the forest had pegged their numbers at 790 with 440 in Bangladesh and 350 in India. The camera trapping method has replaced the pugmark technique as it is more accurate and provides visual evidence of the tigers with pictures of their unique stripes.

The agencies captured 105 individual tigers on their cameras and based on the photographs, their density, habitat and prey base, it was estimated that 182 tigers are present in the Sundarbans.

According to the study, an area of 2,912 square km was assessed by camera traps.

Camera trapping was carried out in eight blocks located in Sarankhola, Satkhira, Khulna, Basirhat, Ramganga East, West and Sajnekhali Ranges. Of these eight, three are in Bangladesh and five in India. Camera trap locations were chosen carefully.

AT A GLANCE Total number of camera trap locations: 528 Individual tigers captured on camera: 105

Considering factors such as tidal interruptions, human disturbance and width of river channels. "Wide water channels of more one km on most sides were selected to set up cameras as tigers avoid them. The cameras were also fixed near brackish water, in elevated places, river bends, regular channel crossing paths frequented by tigers based on local knowledge," the report said.

Data from radio-collared tiger suggests that tigers in general show avoidance in crossing channels wider than 600m and also they are most active from 5am to 10am.

Across the studied blocks in Bangladesh and India, the tiger density was 2.85 per sq.km.

Threats

During the study, it was observed that constant movement of vessels is an everyday threat. "The constant movement of boats can become potential barriers to dispersal of tigers between islands leading to fragmented and isolated tiger populations within Sundarban," the report said.

Pollution is a big threat to the large mangrove forest along with the commercial vessels and boats carrying passengers. The vessels plying in Sundarbans often carry cargo like oil, fly-ash, cement and fertilizer.

The report has highlighted than more than human interference, it is climate change and resultant rising sea levels that is a more potent and direct threat to the landscape. Between 1973 and 2010, 170 sqkm of coastal land was lost in the Sundarbans.

AT A GLANCE Sundarban Biosphere Reserve Indian Sundarban cover an area of 4267 sq.km of mangrove forest which is within the two districts 24 Paraganas South and North of the state of West Bengal. The Indian Sundarban has been declared as 'Sundarban Biosphere Reserve' under the UNESCO and Man and Biosphere Reserve.

A part of the biosphere reserve is the Sundarban tiger reserve spread across 2585 square kms which is further divided into Sundarban national park, Sajnekhali wildlife sanctuary and the Basirhat buffer zone.