Around 50 years ago, tribal people in Simlipal, which is located in northern Orissa, began seeing black tigers. No one believed them at first. Now, years later, genetic research done at a Bangalore lab has tracked down the reason for the evolution of this rare creature.
Such tigers are not wholly black. Instead, their stripes are so broad that they seem to join, making the orange coat almost disappear. Research done at the National Centre for Biological Sciences (NCBS), Bangalore shows that 37% (that’s more than one-third) of the tigers in what is now Simlipal Tiger Reserve have these wide, merged (joined together) stripes. This is called ‘pseudo-melanism’ (pseudo = false; melanistic = dark/black coloured).
What’s common to all these tigers?
They are the result of mutation of a single gene that is called Taqpep in short. What does this mean? Genes are found inside the nucleus, the beating heart of every living cell. Cells, as you know, are what all living creatures are made of, so genes are found in each cell. They are made up of DNA and assembled together in strands. Many genes contain instructions for the body to produce proteins, and it is their action that is responsible for the colour of your eyes, skin and hair, body height and other features. Genes are also inherited – this means that you get some of them from your dad and the rest from mom, and it is through them that features are carried forward from one generation to another.
For the tigers of Simlipal, this is the reason that there are some ‘black’ tigers in every generation. Different variations in same gene Taqpep are known to cause similar changes in coat colour in several other species of cats including cheetahs and feral cats.
The researchers at NCBS also found out that the gene doesn’t exist outside of Simlipal, and this fact tells us another tale of India’s tigers.
Long ago, tigers could walk from one end of India to the other if they so wished (none did as far as we know!). That was because all forests were interconnected. Now tigers live in islands of forests that are not connected. Simlipal for instance is 500 kilometres away from the next closest tiger population. So, that is why the ‘black tiger’ gene has stayed within Simlipal. Such isolation is not a good thing. The reason that so many tigers there have this special gene is because they form pairs and have babies within the same small group. But what if a gene mutation were to cause a disease? Then a lot of tigers wont be able to escape it.
The mystery of the ‘black tiger’ may have been solved, but it has left us with questions about bigger problems that face India’s tigers.