Mystery Behind Odisha's Rare, Endemic 'Black Tigers' Unraveled: All You Need To Know

More than half a century ago, when the tribals of Similipal in Mayurbhanj district of Odisha reported sightings of ¡°black tigers¡± ¡ª their stripes almost fused together in patches threatening to obliterate parts of their burnished orange coats ¡ª nobody believed them at first.

But an estimated 37% of Panthera tigris in the Similipal Tiger Reserve (in eastern India) are pseudomelanistic (another variant of pigmentation), characterised by wide, merged stripes.

Stripes broaden to make the cat look completely black

Putting an end to the enduring mystery behind the ¡®black tigers¡¯ of Similipal in Odisha, researchers have finally identified a single mutation in a gene that causes their distinctive stripes to broaden and spread into their tawny pelt, occasionally appearing entirely dark.

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A team led by ecologist Dr Uma Ramakrishnan and her student Vinay Sagar from the National Centre for Biological Sciences (NCBS), Bangalore, have discovered that the coat colouration and patterning that make the wild cats appear dark boil down to a single mutation in the Transmembrane Aminopeptidase Q (Taqpep) gene.

"Ours is the first and only study to investigate the genetic basis for this phenotype (look). While the phenotype has been talked about and written about earlier, this is the first time its genetic underpinnings were scientifically investigated," Dr Ramkrishnan, professor at National Centre for Biological Sciences, told PTI.

Findings of the research

The researchers combined genetic analyses of other tiger populations from India and data from computer simulations to show that the Similipal black tigers may have arisen from a very small founding population of tigers and are inbred, providing an answer to the question that had perplexed so many.

The study, published in the journal Proceedings of the National Academy of Sciences on Monday, noted that tigers in the Similipal Tiger Reserve are an isolated population in eastern India, and gene flow between them and other tiger populations is very restricted.

The researchers noted that this has important implications for tiger conservation as such isolated and inbred populations are prone to extinction over even short periods of time.

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"They (the black tigers) have not been found in any other places in the wild to the best of our knowledge. Nowhere else in the world," Mr Sagar, a PhD student in Dr Ramakrishan's lab and lead author of the paper, told PTI.

"We used whole genome sequencing from a pedigree (family tree) that includes pseudomelanistic (false coloured) and normally striped individuals to find the mutation responsible for the phenotype," he explained.

What makes such tigers different

The abnormally dark or black coat in such tigers is termed pseudomelanistic or false coloured. The most recent sightings of this rare mutant tiger in Similipal, long considered mythical, was reported in 2017 and 2018. "There are several camera trap pictures. In fact, camera trapping was carried out in 2021 in Similipal," Dr Ramakrishnan told PTI.

The researchers at NCBS teamed up with tiger experts nationally and in other countries and found out that pseudomelanistic coat came down to the genes. They found the black tigers are mutants and are Bengal tigers with a single base mutation.

Benjamin Carey FTS

Different mutations in this gene are known to cause similar changes in coat colour in several other species of cats, including cheetahs. The drastic change in patterning and colouring of the black tiger's coat is caused by just one change in the genetic material DNA Alphabet from C (Cytosine) to T (Thymine) in position 1360 of the Taqpep gene sequence, the researchers said.