Flawed estimation method behind rise in India's tiger count?
In a finding that could dishearten thousands of wildlife lovers, a team of scientists has warned that the big cat populations in India may not be on the rise after all, owing to inaccurate estimation method.
New Delhi: In a finding that could dishearten thousands of wildlife lovers, a team of scientists has warned that the big cat populations in India may not be on the rise after all, owing to inaccurate estimation method.
The India's national tiger survey, which was carried out in in January suggested a 30% rise in tiger populations in just four years (with numbers rising from 1,706 in 2010 to 2,226 in 2014).
Now, a team of scientists from the University of Oxford, Indian Statistical Institute, and Wildlife Conservation Society have for the first time revealed the shortcomings in 'index-calibration' method used to determine the wildlife populations suggesting that it can produce inaccurate results.
The team believed that the statistics could be wrong due to flawed counting method as the India's tiger estimations was done using index-calibration.
The 'index-calibration' technique involves using camera trapping and other methods to measure animal numbers in a relatively small region, and then relating this measure to a more easily obtained, inexpensive indicator such as animal track counts by means of calibration. The calibrated-index is then used to extrapolate actual animal numbers over larger regions.
“This study exposes fundamental statistical weaknesses in the sampling, calibration and extrapolations that are at the core of methodology used by the Government to estimate India's numbers, thus undermining their reliability,” Dr Ullas Karanth, a co-author from the Wildlife Conservation Society, was quoted as saying.
To investigate index-calibration the team created a mathematical model describing the approach and then tested its efficiency when different values, representing variations in data, were inputted.
Under most conditions the model was shown to lose its efficiency and power to predict. The team then tested this mathematical model on a real world example: attempting to derive tiger numbers from fieldwork data. The index-calibration model was shown to be unreliable again, with any high degree of success shown to be down to chance.
To investigate index-calibration, the team created a mathematical model describing the approach and then tested its efficiency when different values were put in.
They found the model lost its efficiency and power to predict most of the time. The mathematical method was proved to be inaccurate even when tested on real world examples.
The findings, published in the journal Methods in Ecology and Evolution, aim to help ecologists and conservationists to address the global challenge of counting rare and elusive animals.