Counting tigers by studying droppings

After years of searching for a foolproof method of counting tigers, officials in the Sundarbans have decided to analyse the animals’ droppings — or scat — to estimate the big cat’s population in the delta.

Traditional methods like pugmark collection and ‘camera trap’ techniques have not yielded satisfactory results because of the muddy terrain and thick mangrove growth.

“Estimating tiger population through DNA analysis of scat is nearly flawless,” said P K Vyas, director, Sundarban Biosphere Reserve. “Scat, two to three days fresh, contains cells of the animal that can help differentiate it from other animals with 99 per cent accuracy.” This method will be used in the next tiger census, likely in February.

In addition, camera trap techniques will be applied.

A government report on tiger census, published this year, puts the population at under 1,500, down from more than 3,600 in 2002. There was good news recently, though. More than 15 new tiger cubs were sighted at Dudhwa reserve, Uttar Pradesh.

The Sundarbans delta is spread over 4,200 sq km. Tigers are estimated to inhabit a 3,500-sq-km area. Scanning the forest for scat will be a challenge. At some places, visibility is restricted to barely a metre due to the thick vegetation.

“The DNA method is also expensive. And it entails great risk for census workers,” Vyas said. “We need to provide them with protective gear to avoid getting mauled by animals.”

Furthermore, the method may not give an exact count. Some droppings would be washed away, some may be in inaccessible areas, Vyas said. “But if repeated over the years, it’ll take us closer to the exact number.”

Inputs from Sukumar Debnath