How many tigers are there really?
Official estimates may have more to do with wishful thinking than rigorous science.
New analysis casts doubt on official claims that tiger numbers have doubled in India over the last decade.
Last July, the Indian government announced that the country had fulfilled its pledge, made at the 2010 Tiger Summit in St Petersburg, to double its tiger population within 10 years. The official figure is now 2,967.
Arjun Gopalaswamy, a statistical ecologist and advisor to the Wildlife Conservation Society, is the lead author of the new analysis. He says the work was prompted by doubts that such a steep population growth was possible given what is known about the ecology of large mammals.
It identifies flaws in the underlying methods, which introduce errors such as high rates of double-counting.
“We suggest there’s been a tendency to look for positive results,” says Gopalaswamy. “We call it a motivation bias.”
Certainly, the pressures to meet the target have been considerable. “India is this last hope – with Nepal and Bhutan
– of keeping a viable population of tigers alive, let alone doubling them,” says Julian Matthews, executive chairman of the charity TOFTigers. “Doubling tiger numbers is an easy sell, but it’s a damn-sight harder in practice.”
However, he’s “comfortable” that the numbers from tiger reserves are broadly accurate. “It’s everything in between that is less reliable.”
Gopalaswamy is not convinced even of that. Part of the problem is a lack of transparency, he says. “These reports are not written like scientific papers, where the methods are clearly laid out so you can follow exactly how they did it.”
India’s National Tiger Conservation Authority has now admitted to methodological flaws and pledged to “bring more accountability, transparency and scientific robustness” to the surveys.
“The best thing India could do now is allow a set of independent scientists to see the data and see what they make of it,” says Matthews. “That would clear the air.”
So how many tigers are there? Gopalaswamy says it’s not possible to come up with a number on the information available. Matthews, though, doubts it’s much different to the official figure. But, he adds, “More important than getting the numbers right is getting the ecology right and protecting it.” Stuart Blackman
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“There’s been a tendency to look for positive results. We call it motivation bias.”