The study says that counting tiger "pugmarks" or track prints, a technique developed in 1966 but never published in a scientific journal, is still used by India's government as the exclusive method to count tigers. Yet the method is scientifically flawed for several reasons.
The authors of the study charge that by setting itself the impossible goal of counting all individuals of a secretive species across thousands of square miles of rugged landscape, the "pugmark" census is doomed to failure. This in turn has led to field managers reporting increases in tiger numbers even in cases where mounting evidence showed protection had deteriorated.
"Trying to estimate tiger numbers across India using the pugmark census is an impossible task," said the paper's lead author Dr. Ullas Karanth, a WCS conservation zoologist who has studied tigers for the past 20 years. "Money and effort spent on counting pugmarks can be better used on simpler, statistically sound monitoring methods that can really help save tigers."
According to the study, in 1999 alone, the Indian government spent some $10 million on tiger-related conservation measures, while another $1.75 million came in non-governmental donors. However, the authors say that it is virtually impossible to measure the effectiveness of this investment using traditional monitoring methods.
Karanth and his co-authors say that "statistically robust" alternatives should be adopted to monitor tigers in India, where most of the world's tigers still live. These include sample surveys to map the presence or absence of tigers throughout their range. For important reserves that contain tigers, park personnel should use "encounter-rate" surveys, which monitor tigers by counting samples of not only tiger tracks, but also other signs. Such simple indices can track tiger numbers adequately for management purposes.
Lastly, in a few critically important reserves where there is need to know actual tiger numbers, the use of advanced techniques such as remote "camera-traps," and measuring prey densities is essential, the paper argues.
The Wildlife Conservation Society is working to save tigers throughout their range, with field conservation projects in not only India, but also the Russian Far East, China, Thailand, Myanmar, Indonesia and Malaysia. Earlier this month, at its flagship Bronx Zoo headquarters, WCS opened "Tiger Mountain," a spectacular three-acre, interactive tiger exhibit that links zoo visitors with some of these field conservation efforts.
CONTACT: Stephen Sautner (718-220-3682; ssautner@wcs.org)
John Delaney (718-220-3275; jdelaney@wcs.org)
Journal
Animal Conservation