The scientists at the Wildlife Institute of India (WII) have found significant differences between the tigers found in the Sunderbans delta and those found in the rest of the country. They feel that the smaller and lighter tigers of the deltaic region could have evolved into a sub-species of Royal Bengal Tiger,as the big cats have adapted to the ecological conditions of their habitat,which remains inundated by the tidal waves. The tigers found in the Sunderbans could be a different sub-species of Royal Bengal Tiger (Panthera tigris tigris),which is found all across the India, said Dr Yadvendradev Jhala,a scientist at the WII who is examining the reasons that could have led to the tigers developing deviant features. There could be genetic or adaptive reason behind this. For a different species,it takes about one million years to evolve but for a different sub-species can evolve in 20,000 to 50,000 years, said Jhala. On Saturday,a six-year-old male tiger got trapped at Sahibghata in the Sunderbans. But what took the forest officials by surprise was that the tiger weighed only 98 kg. The tigers body parts are smaller as compared to other adult tigers found in terrestrial areas, said Subrat Mukherjee,Field Director,Sunderban Tiger Reserve. According to the scientists at WII,an average big cat weighs about 250 kg,whereas tigers in Sunderbans weigh about 100 kg. The reduced weight helps these tigers to move swiftly and they do not sink in the mud,said Jhala,and added that a leaner,smaller body helps them to reduce their requirement for food,which is less in the area. Their prey base comprises spotted deer,wild boar and monitor lizards. They also eat crabs and other aquatic animals. Moreover,with the area having scarce fresh water sources,tigers in the delta are said to survive on saline water. Another unique feature of the tigers in Sunderbans is their significantly smaller girth of neck. While the girth of tigers necks found in rest of the country is 75 cms,in tigers of the delta it measures only 45 cms. This was the chief reason that the radio collars made to track the tigers did not fit the tigers of Sunderbans,and now the state forest officials are looking for a customised radio collar. Scientists,as well as forest officials,are carrying out various studies like osteological studies,DNA analysis of blood,hair and scat to ascertain that if the tigers differ from Panthera tigris tigris. In the past too,many extensive studies on the Sunderban tigers have been conducted to ascertain how they could swim long distances and negotiate marshy and spiky terrains. So far,three tigers in the delta have been fitted wit radio collars and their movements are being monitored. As some of them have strayed to neighbouring Bangladesh,officials have concluded that their territory spreads between 100 to 120 square kilometres a vast difference from the territory of the terrestrial tigers. The territory of female tiger is based on the prey available. In case of terrestrial tigers,it is 20 sq km whereas in case of Sunderban tigers it is about 100 to 120 sq kms as the prey is scarce, said Jhala.
