NEW DELHI--India may be the last stronghold for the endangered Bengal tiger. But the way the government keeps tabs on the majestic animal is so flawed as to be nearly worthless for conservation purposes, say a group of scientists.
"Three decades of tiger monitoring has basically failed in India," declare the authors of a report in the current issue of Animal Conservation, published by the Zoological Society of London. The study, by nine U.S. and Indian scientists, goes public with long-running concerns among conservationists about India's use of pugmarks--tiger footprints--to count the big cats in the wild.
Pugmarks were thought to be unique, allowing trained eyes to track specific animals. But the authors say that even experts flunked a recent controlled test in which they were asked to distinguish the pugmarks of individual tigers. To better measure tiger trends, they recommend that India adopt statistically sound sampling methods such as transects and modern camera traps set in prime tiger habitat. But Indian officials defend their use of pugmarks, which are preserved in plaster of Paris casts or through tracings, and say they are taking steps to make the technique more accurate.
India is believed to be home to the largest number of royal Bengal tigers, which a century ago numbered about 100,000. Its latest estimate of 3642--out of a worldwide population of roughly 7500 tigers--is roughly 5% lower than 3 years ago. That decline has called into question the effectiveness of the government's $7 million Project Tiger, which carries out conservation activities in 27 designated reserves and elsewhere throughout the country. The new report says that pugmarks fall short as a counting tool because they are drawn from an "unknown fraction" of the 300,000 square kilometers of tiger habitat in India and are difficult to locate in some terrain, including hard or rocky soil as well as mangrove swamps.
Rajesh Gopal, director of Project Tiger, defends the use of pugmarks as "in tune with the local conditions" and says that the technique will be refined as part of a $1.1 million project now under way to map all tiger habitats. But Melvin Sunquist, an expert on tiger ecology at the University of Florida, Gainesville, says "there is too much room for identification error in the pugmark approach because of variation associated with substrate, travel rates, and stride length." For the method to work reliably, he says, park managers would need to be able to recognize each individual tiger in their area, an improbable standard.