Contrary to speculations that Sunderbans tigers are a species of their own, with distinct morphological characteristics, a recent study by the Wildlife Institute of India (WII) has found that the gene pattern of the Sunderbans tiger is identical to the big cat population of the central Indian landscape and have been isolated only 300-1000 years back from the latter.
The study, ‘Tigers of Sunderbans Tiger Reserve: Is This Population a Separate Evolutionary Significant Unit’, has been conducted by wildlife scientists Dr SP Goyal and researchers Sujeet Kumar Singh and Sudhanshu Mishra from WII.
The study claimed that historical events, change in the land-use patterns and human pressure may have isolated the Sunderbans tiger population from their counterparts in Central India. But their gene pattern is identical to the big cat population found in the States of Madhya Pradesh, Maharashtra, Chhattisgarh and parts of Andhra that largely comprise central Indian tiger landscape.
A precursor to this study was conducted in 2009 by US wildlife biologist Adam Barlo. It had observed that the Sunderbans tiger is morphologically distinct in terms of skull and body size. Hence, the population can be evaluated further to determine if it is an evolutionary significant unit.
But the latest study has put to rest all such possibilities for the present. It has used methods of DNA Haplotyping and fragment analysis. Haplotypes refer to unique characters present in a genetic composition of a particular tiger population.
According to Goyal, Sunderbans tiger showed identical “allelic” or gene pattern when compared to the tigers in Bandhavgarh, Kanha, Pench Tiger Reserves in Madhya Pradesh or those of Tadoba and Nagzira in Maharashtra. He further stressed, “Geologically, Sunderbans do not have a history as old as central or northern India, hence it is possible that the mangrove tigers have isolated from central India landscape.”
According to experts when an animal is isolated for a period of one million years it can be classified as a different species; while one that is genetically separeted for 20,000-50,000 years can be termed as a different sub-species.
They pointed to an earlier study by wildlife scientists, John Seidensticker, Sandeep Sharma and Hemendra Panwar. It claimed that while tigers populated central India about 10, 000 years ago, their population subdivision began only about 1000 years ago and accelerated only 200 years ago owing to habitat fragmentation. The morphological variation in Sunderbans tigers is thus only an ecological adaptation to survive in the unique mangroves habitat, they added.