An exercise is underway in the Sundarbans to estimate the population of the delta’s apex predators.

Not the tiger, which sits at the top of the food chain on land, but the estuarine crocodile (Crocodylus porosus) – the world’s largest living reptile – which dominates the salt waters.

This exercise is taking place after 12 years. A forest official said around 140 crocodiles were last estimated in 2012.

Over four days last month, small teams on boats scanned nearly 900 km of river banks and creeks for physical sightings.

“We had 22 teams, of which 14 were deployed for the Sundarban Tiger Reserve and eight for the South 24-Parganas forest division. Each team had forest department personnel as well as representatives from local wildlife NGOs,” said Nilanjan Malik, director of the Sundarban Biosphere Reserve.

STR’s Sajnekhali and Basirhat ranges and South 24-Parganas division’s Matla range were covered on January 17 and 20.

National Park East and National Park West and Raidighi and Ramganga ranges of South 24-Parganas division of STR were covered on 20 and 21 January.

The survey was halted due to cloudy weather on 18 and 19 January.

“Each boat covered a distance of 40 km in two days. Data compiled based on physical vision and health of the habitat is now being prepared. The preliminary report is expected on February 6 and the final report at the earliest,” Mallick said.

Unlike the tiger census, where images captured by cameras are fed into software that uses statistical tools to estimate the population, crocodile population estimates are based on physical sightings and sign surveys and habitat assessments. But, it is done.

Winter is an ideal time to survey crocodiles as this is when they are most often seen sunbathing along the banks of rivers and creeks.

“The tidal calendar is the key to any such exercise. Days when the tide is at its lowest are ideal for physical surveys,” said B.C. he said. Chaudhary, a former scientist at the Wildlife Institute of India and a member of the Crocodile Specialist Group at the International Union for Conservation of Nature (IUCN), provided technical expertise for the population estimation.

Chaudhary organized a training camp for the team members.

The entire area scanned (about 900 km) has been divided into “large, small and medium” habitats, he said.

“Based on physical sightings, we will come to a basic index of the number of crocodiles per kilometer in each habitat. That data will be expanded to the larger Sundarban habitat (which covers 4,000 square km of Indian territory). The actual sighting in 900 km should be around 60 per cent of the total population, Choudhary said.

“This is an assessment of the population trend, not a campaign to get accurate numbers,” he said.

He said the probability of a crocodile being counted twice is low because, like tigers, crocodiles are very territorial.

The estuarine crocodile is found in eastern India, Southeast Asia and northern Australia. There are instances of males growing up to 20 feet tall and weighing over 1,000 kilograms.

“In the Sundarbans, the average length of an estuarine crocodile is about 12 feet. Local people and our people have seen a male growing up to 15 feet in the past,” said a forest official.

“In addition to their size, their high tolerance to salinity distinguishes saltwater crocodiles from their cousins such as alligators, crocodiles and caimans. Storms and high tides push them out to sea. They can survive the increase in salinity. But their ideal habitat is brackish water,” he said.

Bengal Chief Wildlife Warden Debal Roy said: “Like the tiger, the crocodile is also a Schedule I animal. The tiger is the apex predator in the terrestrial ecosystem. The estuarine crocodile is the apex predator in the aquatic ecosystem. Assessing crocodile populations is a study of the entire aquatic ecosystem.

Saltwater crocodiles have the highest bite force among living animals. Their bite is about four times stronger than that of a tiger or lion and, according to an international study in 2012, could rival that of the mighty Tyrannosaurus rex.

In 2011, a tiger was killed by a crocodile in the Dobanki camp of the Sundarban Tiger Reserve.

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