They have fascinated wildlife enthusiasts and scientists for centuries. Now, scientists say they may have pegged down a genetic mutation that gives Odisha's 'black tigers' their distinctive look. A team led by ecologist Dr Uma Ramakrishnan and her student Vinay Sagar from the National Centre for Biological Sciences (NCBS), Bangalore, discovered that the coat colouration and patterning that make the big cats appear dark were due to a single mutation in the Transmembrane Aminopeptidase Q (Taqpep) gene. Dr Ramkrishnan said the study is the first to investigate the "genetic underpinnings" responsible for the phenotype by combining genetic analyses of other tiger populations from India and data from computer simulations.
The researchers concluded that Similipal black tigers may owe their origins to a very small founding population of tigers and were inbred.
Published in the journal Proceedings of the National Academy of Sciences, the study noted that tigers in the Similipal Tiger Reserve are an isolated population in eastern India. The restricted gene flow between them and other tiger populations is significant for tiger conservation due to their increased vulnerability to extinction over even short periods of time.
"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," Sagar, a PhD student in Dr Ramakrishan's lab and lead author of the paper, told news agency 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.
Reports of black tiger sightings and their capture in central and northeast India by locals and British hunters date back to the late 1700s.
"There are several camera trap pictures. In fact, camera trapping was carried out in 2021 in Similipal," Dr Ramakrishnan told PTI.
As of 2018, India had an estimated 2,967 tigers and photos captured from Similipal the same year showed three 'pseudomelanistic' tigers. The only other black tigers outside of Similipal in India were born in captivity at the Nandankanan Zoological Park in Bhubaneswar, Ranchi Zoo, and Chennai's Arignar Anna Zoological Park.