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New protocol to minimize error in counting tigers

In a bid to minimize errors on estimation of tiger population, the National Tiger Conservation Authority has made coverage of entire tiger reserve a must for the next phase of big cat population estimation.

delhi Updated: Apr 15, 2012 14:46 IST
Chetan Chauhan

In a bid to minimize errors on estimation of tiger population, the National Tiger Conservation Authority has made coverage of entire tiger reserve a must for the next phase of big cat population estimation.




Number of Indian and foreign tiger scientists have raised doubts over the latest tiger estimation figure of 1,706 putting a question marks over the methodology adopted. In most tiger reserves only the core-critical area was surveyed for tiger estimation.



Taking the criticism into account, the NTCA has updated the methodology and prescribed coverage of entire tiger reserves either by camera traps to take pictures of the animals or through DNA testing of the fecal.



“If the survey area is very large, tiger population size can be obtained by sampling a minimum block of 400 square kilometers at a time,” says the new tiger estimation guidelines circulated to the state forest departments governments.



The guidelines also say that if deployment of camera traps in an entire reserve or parts of it is not feasible for any reason, fecal DNA samples may be collected over the entire tiger reserve for capture-recapture analysis, methodology to cross check DNA findings with camera trap pictures.



To minimize the errors arising of keeping the camera traps open for a longer duration, the authority has prescribed the duration for which the camera trap should be opened and closed.



“Keeping the camera open can lead to higher estimation of tigers,” said K Ullas Karanth, director Bangalore based Centre for Wildlife Studies, who had questioned the methodology of earlier tiger estimation.



A key to estimate the tiger population correctly is the prey population. A particular habitat can support a certain number of prey population. Higher or lower prey population indicates lesser number of tigers. And, experts in the past had raised eyebrows over NTCA estimation of the prey population.



The NTCA has stipulated new software called DISTANCE to estimate prey density. The forest departments have been asked to ensure that the date on prey population to be feed into the software should be done with the help of experts to prevent errors.



The state forest departments have been asked to take help of experts such as scientists from the Wildlife Institute of India to analyse the data collected. The experts should have knowledge of capture-recapture methodology and fecal analysis.



Karanth said the new NTCA protocols will enable state forest departments to formally collaborate with qualified scientists, and enable them to move up a ladder of technical progress. “They will also move from estimating minimum numbers of tigers to robust estimates of population density, change in numbers over time, survival and other crucial parameters,” he said.