Focus on tiger prey base in Sunderbans

KOLKATA: The prey base in Sunderbans has always been under scanner. But a study by Wildlife Institute of India (WII) may actually blow the lid off the issue. If an estimation by the WII is to be believed, about 15 spotted deer per square kilometre (sq km) are surviving in Sunderbans currently. "We have initiated a study on tiger density and prey base in Sunderbans and will come out with the final report in a couple of months. But according to initial investigations, we fear there are not more than 15 deer per sq km," says Y V Jhala of WII.

A recent study by Wildlife Protection Society of India (WPSI) says a full-grown wild tiger needs to eat 50 cheetals a year to survive. "A herd of 500 cheetals is required to provide a sustainable outcome of 50 cheetals per tiger. In other words, 500 cheetals can provide a single tiger 50 cheetals a year for food," says Belinda Wright, executive director, WPSI.

Sunderbans Tiger Reserve (STR) is spread over almost 2,580 sq km, of which nearly 35% is water. Taking into account the rest of forest land, not more than 25,000 deer are reportedly there in Sunderbans.

According to Wright, a prey base of 25,000 cheetals is only enough for 50 tigers. Is the present number of big cats in Sunderbans around 50? The question remains unanswered. And where are the cheetals vanishing and why? The mystery only intensifies.

According to Jhala, herbivores cannot take salinity after a point and that is the main reason behind the shrinking prey base.

Director of Sunderbans Biosphere Reserve, Pradeep Vyas, said: "Once we receive an official intimation, we will definitely look into the matter. No study has yet been done on Sunderbans' prey base and we are waiting for the WII report." According to him, not only deer, tigers depend on wild boars and monitor lizards too for food.

Going by Biswajit Roy Chowdhury of Nature Environment and Wildlife Society, salinity is not only a problem for the deer but it's dangerous for tigers as well. "Salinity has increased by almost 15 times in last 10 years, which is dangerous for both deer and tigers," he says.

Quoting a study by scientists Dr Ullas Karanth and George Schaller, Bangladesh-based tiger expert Monirul H Khan says: "There is always a natural balance between the prey and number of tigers. And 500 deer can provide sufficient food base to only one tiger, keeping in mind the fact that the breeding rate of deer is always balanced by the killing rate of tigers."

Bangladesh forest department recently said there are 70,000 to 80,000 cheetals in their part of Sunderbans, which according to Khan is not capable of providing sufficient food base to 419 tigers there.

The numbers game in Sunderbans still remains a million dollar question. Is the 2004 census figure, that says the mangrove forest has 274 tigers, believable? The figure, which has been contested fiercely, offers a case study. In the 2008 tiger census, the number of Sunderbans tigers could not be included as authentic figures were missing. Though WII is also set to come out with a preliminary report on tiger census in other parts of the country by November-end, Sunderbans will not be included in this. On being asked why, Jhala offered no comment.

Tushar Kanjilal, well-known social worker who spent long years in Sundarbans, has his take. "Prey base is definitely shrinking, but no concrete study has ever been done. But more and more tigers are moving towards the north from south, resulting in frequent incidents of straying," he says.

Former Project Tiger director, P K Sen, says: "We have been repeatedly saying that there is a shortage of prey base in Sunderbans. When WII comes out with the final report, I believe the actual number of cheetals per sq km will be even lesser than 15."

Wright says that poaching of deer should also be taken into account.


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