LANZHOU - More than 50 Chinese zoologists are tracking giant pandas in a wild habitat of Gansu province, hoping to collect DNA samples from the endangered species.

Baishuijiang Nature Reserve, a 220,000-hectare area covered with dense mountain forests in south Gansu, is known as one of the largest habitats for wild pandas.

The third national census of the giant pandas, carried out by forestry authorities from 2000 to 2002, indicated the reserve is home to 117 wild pandas.

In May, Gansu started a field survey on those pandas, hoping to find out more about their living conditions in two and a half years and eventually build a databank containing files on the wild pandas' genetic diversity.

Liu Yong and Wang Jianhong were among a 19-member team who headed into the virgin forests from a panda research base in Qiujiaba last week.

The base, founded in the 1980s, helped rescue eight pandas found dying from hunger or injured in the wild. The pandas were later sent to neighboring Sichuan province.

They trekked more than 10 hours a day in the wild, carrying GPS and other field facilities. The vast expanse of forests is not covered by mobile telecommunications and impossible for vehicles to drive through.

On Monday, Liu and Wang trekked 7 km to check on nine potential panda habitats, taking notes of plants and panda dung along the way.

"We must keep note of how far we've travelled, and make sure we can locate the sites precisely," Liu said. "It's very easy to get lost in the forests."

The two did not spot any pandas, but were delighted to find some fresh panda dung. "They were within three days old and we can extract DNA samples," said Liu.

The samples will hopefully help the scientists figure out the wild pandas' sex ratio and eventually to build a databank of the bears' genetic diversity at the end of the survey.

Baishuijiang Nature Reserve sits on the Gansu-Sichuan border and is only a few hundred kilometers from Wenchuan, the epicenter of a devastating Sichuan earthquake of 2008.

"We'll also study the quake's damages to the pandas' habitat and its impact on the panda population," Wang said.