India used a commonly used method to count tigers and other rare wildlife put the accuracy of such surveys in doubt, said a team of scientists from the University of Oxford, Indian Statistical Institute, and Wildlife Conservation Society.
Criticising shortcomings in the ‘index-calibration’ method that yields inaccurate findings, the team said the flawed census should be corrected. It may be noted that India claimed a surprising 30% increase in its tiger population in 4 years after a January 2015 survey.
The team urges conservation practitioners to guard against these sources of error, which could mislead even the best conservation efforts, and suggests a constructive way forward using alternative methods of counting rare animals that avoid the pitfalls of the index-calibration approach.
A report of the research is published this week in the journal Methods in Ecology and Evolution.
Arjun Gopalaswamy, lead author, said: “Index-calibration relies on the assumption that detection rates of animal evidence are high and unvarying. In reality this is nearly impossible to achieve.”
Dr Ullas Karanth, a co-author from the Wildlife Conservation Society, and a member of India’s National Tiger Conservation Authority, said: ‘We are not at all disputing that tigers numbers have increased in many locations in India in last 8 years, but the method employed to measure this increase is not sufficiently robust or accurate to measure changes at regional and country wide levels.’
The study recommends that estimates from future surveys will be most reliable if designed, a priori, keeping in mind the power of modern, robust, modelling approaches.