New tech to estimate tiger numbers

A new method called camera trapping was deployed initially in southern India by Karanth's team to estimate tiger numbers by photographing them in the wild. Using some remote cameras, tigers were made to take 'selfies' and it assumed that the stripe patterns of each animal is as distinctive as human fingerprints, then after collating a large number of pictures tiger numbers could be arrived at.

This was an expensive but certainly more robust than chasing tiger footprints. Using some sophisticated statistical tools called capture and re-capture techniques and pattern recognition software, more reliable tiger numbers were arrived at.

This technique showed that tiger numbers were dipping drastically and alarm bells rang out that the tiger may go extinct by the turn of the millennium. But, thanks to some very active policing by tiger experts like Rajesh Gopal, the head of the National Tiger Conservation Authority, it helped bring back the tiger from the brink of extinction.

This method of using camera traps was then adopted by the WII and deployed in all tiger habitats and the latest estimate of 2,226 adult tigers in India is basically an outcome of using camera traps.

Yet in some areas, especially where cameras are liable to be vandalised, or in areas where Naxal violence dominated it was impossible to use camera traps, this was now well into the 21st century and DNA techniques had been mastered.

Experts started using DNA techniques to estimate the tiger numbers, for this either tiger hair is collected or the droppings of tigers are collected and then subjected to some nifty biochemical analysis. While the droppings or the poop of tigers contain a lot of remains of the animals it may have consumed but the 'scats', as the droppings are called by scientists, also have tell-tale signatures of the tiger.

Scientists bring back bag loads of smelly tiger shit and then subject it to modern biotechnological procedures to literally arrive at the individual tiger numbers. This was likely to become the gold standard since it is hard to go wrong with DNA finger prints. This technique of using tiger droppings has been mastered at two top of the line laboratories in Hyderabad and Bengaluru.

Now the group from WII has questioned the veracity of the techniques used for DNA-based estimation in a cheekily titled paper 'Schrodinger's scat' a spin on the famous 'Schrodinger's cat' a 1935 thought experiment by well-known physicist Erwin Schrodinger which presented a theoretical scenario of a cat being simultaneously dead and alive.

Jhala reports in this recent paper that the researchers were wrongly identifying leopards as tigers. A fatal error that can lead to the bloating of tiger numbers since leopards are far more common. In a statement, Jhala says, ‘What are the implications of these findings? The authors point out that these erroneous (DNA) primers have been used in many prestigious publications. Due to the possibility of leopard scats being misidentified as tiger, this could lead to inflated tiger population estimates.

For instance, the historical population of tigers south of the Narmada has been estimated at around 50,000, in one study using these primers. Given that these studies were conducted with the erroneous primers, this number may need to be revisited.’