Previous population estimates had also relied on panda dung, but those analyses had looked for different-size bite marks on partially digested bamboo stems.
"Even the ecologists working in the field all the time rarely see pandas, which is why they have used poop [in surveys] as well," he said.
"Pandas defecate up to 40 times a day."
Bruford says the DNA fingerprinting technique provides a more accurate picture than an analysis of the dung's content.
"You get a standard genetic profile, just as you would use to try to catch criminals," he said.
The DNA tests indicated that some 66 pandas now live in Wanglangmore than twice the figure estimated by a 1998 survey.
The researchers say that population growth cannot explain such a big difference in numbers and that the previous survey likely underestimated the size of the Wanglang population.
Writing in this week's issue of the journal Current Biology, the team says similar disparities may well exist for other key giant panda reserves. This means there could be many more pandas throughout China than previously estimated.
"There may be as many as 2,500 to 3,000 giant pandas in the wild," the team concluded.
As well as allowing researchers to identify individual pandas, the unique DNA profiles provided other information, such as an animal's gender and the size of its territory.
The study also showed that the Wanglang pandas have plenty of genetic diversity, despite concerns among conservationists that habitat loss has isolated some wild panda populations, leaving them vulnerable to inbreeding.
"We didn't find any evidence for that in our study," Bruford said.
He notes that wider DNA profiling of wild pandas should give a better indication of the extent to which panda conservation efforts in China are helping to boost numbers.
"If we really want to see whether or not the population is genuinely increasing throughout its range, then we clearly need to do this in other reserves," he said.
WWF, the international conservation organization that has the popular black-and-white mammal as its symbol, welcomed the new study.
Mark Wright, conservation science advisor at WWF U.K., described the team's findings as "potentially exciting and promising news." But, he says, wild panda numbers still remain at "perilously low" levels.
WWF highlights habitat loss as the major long-term threat to the survival of giant pandas in the wild.
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