Men on boats scanning the Sundarbans for signs of the apex predator on land earlier this month were also looking for traces of the top predator in the waters of the mangrove delta.
The sign and transect survey phase of the quadrennial pan-India tiger estimation in the Sundarbans coincided this year with the annual saltwater crocodile estimation exercise in the delta, allowing forest officials to combine resources for both exercises.
Between December 11 and 13, small teams on boats scanned the delta for direct sightings and indirect signs of both tigers and crocodiles.
Trap cameras have already been placed across the Sundarbans as part of the national tiger census. Between November 25 and 30, a total of 1,484 all-weather night-vision cameras (742 pairs) were installed at strategic locations across the mangrove delta. The cameras will remain in place for 45 days and will be retrieved in the second week of January, forest officials said.
“Trap cameras are an integral part of the tiger survey. However, for crocodiles, we mainly depend on direct sightings and indirect traces,” said Justin Jones, deputy field director of the Sundarban Tiger Reserve (STR).
“As resources were already being deployed for the tiger count, we decided to use them for crocodile estimation as well. There is a very small window for the crocodile survey because it depends on tidal flow determined by lunar cycles. Low tide is the ideal time for the survey,” Jones said.
According to the 2025 census, the estimated population of saltwater crocodiles in the Sundarbans is between 220 and 242. A forest department official said the exercise was intended to assess population trends rather than arrive at an exact figure.
The 2024 count had placed the crocodile population between 204 and 234. That survey was conducted after a gap of 12 years. The previous census, in 2012, had estimated the population at around 140, the official said.
Of the nearly 1,800km of creeks in the Sundarban Biosphere Reserve, the survey covered around 1,168km — more than 60% of the total creek length considered significant, defined as creeks with a high-tide width of up to 200m in forested areas.
The biosphere reserve includes the STR and the South 24-Parganas Forest Division. While 18 teams were deployed in the STR, eight teams covered forest areas under the South 24-Parganas division.
“Data collection will take a couple of months, and analysis will take some more time. The final report on the crocodile estimation should be ready by July 2026,” a forest official said.
The all-India tiger estimation is a much larger exercise. Its report, to be published by the National Tiger Conservation Authority, is not expected before the end of 2026, sources said.
Apart from direct and indirect sightings, the crocodile survey also recorded data on salinity levels, surface water and ambient temperatures preferred for basking, creek widths, bank slopes and vegetation.
The 2025 report showed that crocodiles preferred creeks with a high-tide width of 10 to 130m and a salinity range of 10 to 23 parts per thousand. The preferred ambient temperature for basking during winter was between 20 and 30° Celsius.
The survey counts adults and juveniles. Hatchlings are sighted but not included in the population estimates. There is little chance of an individual being counted twice because, like tigers, crocodiles are territorial, a forest official said.