A new study by a team of Indian and British scientists has found that there is a decrease in the genetic diversity among Indian tigers over the last 200 years.
The study has important implications in conservation studies and also provides genetic proof of the fact that the number of tiger has decreased. “In pre-Moghul era, there were possibly over 50,000 tigers in southern and central India alone,” said Dr Ullas Karanth, Director for Wildlife Conservation Society and Centre for Wildlife Studies (WCSCWS).
To ensure that the genetic pool remains diverse, one needs to ensure that tiger reserves have interconnected corridors.
Dr Uma Ramakrishnan, lead author of the paper and faculty at National Centre for Biological Sciences (NCBS), Tata Institute of Fundamental Research, Bangalore, said, “Genetic diversity does not play a role in decreasing tiger numbers. However, it can give indications if numbers have decreased recently, as we have studied in our papers in 2009 and 2013. When genetic variation is low, it indicates that population size/ numbers have decreased in the recent past. Indian tigers show genetic signatures of population declines. But these are historical declines, over the last 200 years.”
The scientists studied DNA samples of the tigers from the last 200 years till now. They found a very high number of historical mitochondrial (Mitochondria is an organ in the cell) DNA variants, 93 per cent of which are not detected in modern populations.
“The most concrete way in which genetic studies can assist conservation are population size estimation using genetic samples and genetic investigation of connectivity between populations. The latter helps us understand how easy it is to move between populations for tigers,” said Uma.
According to Karanth, “Key elements necessary for long-term tiger conservation such as strict patrolling, fair and voluntary resettlement of people in critical tiger habitats are being implemented well. Tiger numbers are recovering. A very good example is Bhadra tiger reserve in Karnataka. At other places, tigers are being lost.”
There are probably around 3,000 wild tigers globally, of which 2,000 are in India. Estimates based on the government tiger census suggest that numbers are increasing. The estimates based on studies by carnivore ecologists such as Karanth also suggest that in some tiger reserves, numbers are increasing. Overall, numbers probably have increased.
Uma said, “While it is important to think about numbers, from a genetic perspective, just having lots of tigers is not enough. It is also important that tiger populations remain connected to each other through movement of individuals.”
Uma also said, “The tiger retains only 7 per cent of its historical habitat. They are big and need large forests for living.”