Count of Tiger prey base in Sunderbans

Count of Tiger prey base in Sunderbans
Aug 14, 2013, 04.47 AM IST

KOLKATA: After finding the presence of at least 103 tigers in the Sunderbans, a figure more than the official estimates, the foresters now want to back the number with a Prey base of tigers in the Sunderbans, mostly spotted deer and wild boars.

To put to rest all controversy over this, the forest department has undertaken an extensive herbivore estimation in the mangroves from Tuesday.

"We are following guidelines laid down by the National Tiger Conservation Authority (NTCA) to estimate the number of herbivores in the mangroves. Since Sunderbans is a unique landscape, we are banking on river or boat transect method for physical enumeration of the herbivores," said Soumitra Dasgupta, field director, Sunderbans Tiger Reserve (STR).

According to him, it will be a three-phase exercise and continue till October. "This month, the exercise will end on Wednesday. Thirty forest department teams, each comprising three members, will criss-cross the rivers and creeks in the mangroves for visual detection of the prey species," Dasgupta added.

The foresters will also take the GPS location, where the herbivores will be sighted, to determine the area-specific density. Dasgupta said by the end of November they would be able to give a rough estimation of herbivores in the forests.

There were efforts earlier to estimate the number of herbivores in the mangroves. But no concrete methodology could be established based on which a reliable estimation could be given.

In 2011, scientists of Wildlife Institute of India (WII) had carried out boat transects covering an area of only 187 kilometres in the mangroves to determine the prey density. "Each boat transect was repeated for a minimum three times and a maximum six times. Prey density along the creeks surveyed in Sajnekhali and west of STR turned out to be comparatively low with only 13.3 deer per square kilometres," said their report.

But this exercise, Dasgupta said, will cover all the rivers and creeks in the Sunderbans. "During the next two phases in September and October, we will rope in NGOs whose expertise will help give a reliable estimation."

A study by scientists Ullas Karanth and George Schaller revealed that there is a natural balance between the number of prey species and tigers. "A full-grown tiger needs to eat 50 deer a year to survive. Since breeding rate of deer is always balanced by the killing rate of tigers, a block of 500 deer can provide sufficient food base, 50 deer a year, to one tiger," the study had said.

And going by this, Sunderbans needs to have a minimum 50,000 deer to sustain a population of at least 103 tigers.

The forest department is also planning to set up prey breeding centres in the mangroves. Some experts had earlier opined that there should always be a prey base analysis first before setting up such breeding centres.