Scientists and officials of the Sunderban Tiger Reserve are investigating whether the Sunderban tiger is a different sub-species compared to those found in the sub-continent, officials told The Hindu on Sunday.
The Sunderban tiger exhibits certain distinctive morphological adaptations that make it particularly suited to the mangrove habitat of the Sunderban islands. The average size of the adult tigers there is much smaller and it weighs about only 100 kilograms, compared to the heavier tigers elsewhere.
A six-year-old male tiger that strayed into the inhabited areas and captured by reserve officials over the weekend weighed only 98 kilograms. Measurements of its body parts confirmed that the animal has a smaller frame than the tigers on the mainland, said Subrat Mukherjee, Sunderban Tiger Reserve Field Director.
Besides DNA analysis of the cat, Mr. Mukherjee will also study the skeletons of tigers as part of the research.
“We will have to see whether these adaptations are only morphological or whether they are genetic adaptations that will qualify them to be listed as a separate sub-species. For this purpose, the mitochondrial and nuclear DNA of the tigers will have to be studied,” said Y. Jhalla, an expert at the Wildlife Institute of India.
Dr. Jhalla explained that considering the mutation rates that led to a genetic change, usually an animal that was isolated for a period of one million years was classified as a 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 the Sunderban tiger, it was part of a contiguous region with others and was perhaps separated about 500 to 1,000 years ago,” he said.
The leaner frame and lesser body-mass was an advantage for the Sunderban tiger in its habitat, he added.
A smaller animal needed lesser food. Since the main prey of the Sunderban tiger (spotted deer) was a lean animal 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, he said.
“Secondly, less body weight makes it easier for the animal to move around in the muddy terrain of the Sunderbans. If the tiger is heavier, its feet will sink further into the soil as it walks and it will have to expend more energy,” Dr. Jhalla said.