Comparative Study of Sundarban Tiger and Other Bengal Tigers of India

“The Tiger is a large-hearted gentleman with boundless courage and when he is exterminated – as exterminated he will be unless public opinion rallies to his support- India will be the poorer by having lost the finest of her fauna.” – Jim Corbett.

Introduction

The Tiger (Panthera tigris) is an endangered big cat that has been associated with Indian culture and history since centuries. It is undeniably one of the most majestic animals alive. There is no wild animal in the world that evokes feelings of great respect, fear, extreme curiosity or simply that of Nature’s magic in the same breath. The Tiger – whose demographic status is uncertain across its entire distributional range, is present in 13 Asian countries with 70% of the population being present in the Indian subcontinent. Because of their large body size and carnivorous diet, tigers naturally occur at low population densities. Further, wild Tiger populations are now being affected by adverse factors such as prey depletion due to overhunting, tiger poaching and habitat shrinkage and fragmentation.

There are a number of subspecies of Tigers that have been identified and they are as follows:-

• Current living populations:-

1. Indian or Royal Bengal Tiger. (Panthera tigris tigris)
2. Indochinese Tiger. (Panthera tigris corbetti)
3. Siberian (Amur) Tiger.(Panthera tigris altaica)
4. South China Tiger.(Panthera tigris amoyensis)
5. Sumatran Tiger.(Panthera tigris sumatrae)

• Recently Extinct subspecies:-

1. Caspian Tiger (Panthera tigris virgata)
2. Javan Tiger (Panthera tigris sondaica)
3. Balinese Tiger (Panthera tigris balica)

The Royal Bengal Tiger (Panthera tigris tigris) is found in fragmented pockets all across the country. There have been speculations however, that the Tigers of Sundarban are a distinct subspecies and not closely related to the rest of the Tigers found in India.

Sundarbans

A deltaic swatch of low-lying mud and silt, the Sundarbans is a tropical estuarine swamp forest that harbours as many as 65 mangrove plant species, making it the most biodiverse mangrove forest in the world. Nutrients pour into this “food factory” from all sides as flood waters from both the Ganges and the Brahmaputra mix and merge with the southern ocean tides to carve ever- shifting creeks and channels- the veins and arteries of the Sundarbans. Nature respects no international boundary; nor do its wards. Tigers swim easily between Bangladesh and India using the rivers as passageways in their eternal search for food.

“[In Sundarbans] Nature does not obey the rules: fish climb trees, the animals drink salt water; the roots of the trees grow up towards the sky instead of down to earth- And here, the Tiger do not obey  the same rules by which the Tigers elsewhere govern their lives.” – Sy. Montgomery.

The tide is the heartbeat of the swamps, the rhythm of the Sundarbans. Tides govern the life of virtually every living creature that seeks sustenance from this aquatic paradise, from beetles and crabs, to Tigers in whose name all is protected.  The locals of Sundarbans worship the Tiger as God in these saltwater swamps and hence the Tiger is both feared and revered in equal measure.

Comparative analysis of Sunderban Tigers

The Sundarban Tiger exhibits certain distinctive morphological adaptations that make it particularly suited to the mangrove habitat of Sundarban islands. The average size of the adult Tiger is much smaller compared to heavier tigers elsewhere. Measurements of body parts of the tiger confirmed that the animal has a smaller frame than the tigers of the mainland.

According to Y. Jhalla, a  Wildlife Institute of India scientist, “Considering the mutation rates that led to a genetic change, usually an animal that was isolated for a period of 1million years was classified as different species and one that was genetically isolated for between 20,000 and 50,000 years was a different sub-species. In the case of Sundarban Tiger, it was a part of a contiguous region with others and was perhaps separated about 500 to 1000 years ago.”

Sunderban Tigers are Smaller and Man-Eaters- Myth or Reality?

The leaner frame and less body mass [Sundarban Tigers (females) weigh 75-80kg whereas the mainland Tigers weighs 100-160 kg (females)] was an advantage for the Sundarban tiger in its habitat. A smaller animal needed lesser food. Since the main prey of the Sundarban Tiger was a lean animal (Spotted Deer) that weighed only about 50 kg compared to much heavier Sambar or Gaur that were eaten by other Tigers, the animal could make do with lesser food.

Secondly, less body weight makes it easier for the animal to move around in the muddy terrain of the Sundarbans. If the Tiger is heavier, its feet will sink further into the soil as it walks and it will have to expend more energy.  A  study carried out by the Sundarbans Tiger Project, a joint initiative between the Bangladesh Forest Department, Wildlife Trust of Bangladesh (WTB), Zoological Society of London and the University of Minnesota.
and funded by the United States Fish and Wildlife Service Tiger and Rhino Fund had established the smaller size of the Sunderbans tiger.

However recent observations of various tigers over the last few years have cast doubt over this theory. Tigers which have been found  and photographed are as big (if not bigger) as those found in the mainland of India. Where did these tigers come from?  So definitely detailed study and research is required before any conclusion is drawn around this . Currently as we speak, tiger census is being carried out across the country and we sincerely believe if these images are carefully studied (given the large number of such images) , we can come to some conclusion regarding the size of the Sunderbans tigers.

Man -Eaters – A myth

Another popular theory goes that the tigers in Sunderbans are man-eaters.German Biologist, Hubert Hendrichs, suggested that their ferocity might be linked to the saline water they drink.  In 1971, he carried out a three-month study on the Bangladeshi side of Sundarbans. He compared the relative salinity of the water with the locations of known tiger attacks. His data correlated the most frequent attack sites with areas having the saltiest water. Virtually no fresh water is available in Sundarbans except dug rainwater ponds. The tides of the Bay of Bengal flush through all the rivers; in certain areas the water is 1.5 per cent salt. Drinking water so salty may cause liver and kidney damage, Hendrichs suggested, making the tigers irritable. Before he could test this hypothesis, his study was interrupted by Bangladesh’s war of independence, and he has never returned.  So this theory remains inconclusive
Another theory goes like saying that Sundarbans tigers have learnt to eat human flesh because it was brought to them, like an offering, from the holy river Ganges. Before its tributaries were dammed by the Farakka Barrage, this river nourished Sundarbans, and with its waters came the corpses of the dead who had been incompletely cremated at Calcutta’s burning ghats. The tigers could have acquired their taste for our flesh from scavenging.
S Dillon Ripley, the former secretary of the Smithsonian Institution, theorised that Sundarbans tigers may have learnt from fishermen to associate people with food. An ancient fishing method in Sundarbans is to string your net across a narrow creek and wait for the fish to become caught in it as the tide recedes. Perhaps, Ripley suggested, the tigers learnt to raid the fishermen’s nets, and so learned to seek out the fishermen and their boats. Perhaps the fishy smell also attracts the tigers.

So what do ground level statistics suggest ? Had tigers being man-eaters and actively sought out human-beings then number of human deaths would have been in thousands over the years. An estimate provided by the forest department claims that 410 people were attacked by tigers between 1985 and 2010, leaving just 95 survivors. Yes there are deaths that go unreported but even if we consider an equal number (to those that get reported ) or more , then also it is not established that Sunderban tigers are man-eaters!!

On the contrary the deaths caused by tigers are primarily due to the classical case of human-tiger conflict that is prevalent across the country.  Humans enter forests seeking honey (though officially they are allowed for two months only) , they are engaged in fishing (as explained above) and also seek out crabs near the banks . Again we have situations where people without valid permits and documents enter the forests and also they do not restrict themselves to the permitted zones!!  Sunderbans has the distinction of most number of attacks on humans by tigers but that is more due to the continuous conflict situations arising out of livelihood compulsions that force people to venture into the forests. Yes tigers enter villages and one can see big nets being used along the banks of forest islands that are directly opposite or close to human settlement but it cannot be inferred that Sunderban tigers are habitual man-eaters.

Picture : A Sunderban Tigress (Niladri Kundu)

DNA Haplotyping

Wildlife Institute of India, Dehradun conducted a DNA Haplotyping and Fragment Analysis study to determine the genetic pattern of Tigers. Haplotypes are a set of closely linked genetic markers present on one chromosome which tend to be inherited together.  When the DNA haplotypes of the Sundarban tigers were compared with that of tigers of Madhya Pradesh & Maharashtra (Pench, Kanha, Tadoba, Nagzira), the pattern was found to be identical. Interestingly, the study points out that Central Indian Tigers and Sundarban Tigers have the same ancestors, the latter have been found to be different genetically from North Indian Tigers (Corbett NP). There was highest population differentiation between the Royal Bengal Tigers and the Tigers from North of India which proves that the Sundarban Tigers are genetically more close to the Central India big cat population.

Way Forward:

The Scientists say that the Bengal Tigers are actually an isolated population of the Central Indian Tigers. The separation occurred between 300 and 1000 years ago due to historical events, human pressure and land-use patterns. The study definitely opens new doors of exploration for scientists to ascertain the evolutionary history of all separate populations of Tigers in India. There is a need to further analyse the history to understand when the separation of the Sundarban Tiger Population occurred. It also shows how humans have been responsible in a major way separating these Tiger populations.

“Let the Tiger become a rallying point, a compass to lead us away from our impending ecological doom.”

-Diptarka Ghosh

About the Author

Diptarka is a postgraduate in Zoology, from the University Of Calcutta. He is an avid wildlife and nature lover and is interested in working for wildlife conservation in the near future.

Editing by Niladri Kundu