Ranger Jiang Zhongjun, 36, is a calm person who has experienced hundreds of dangerous situations in his 12 years of patrolling the Minshan Mountains in northern Sichuan but the aftershocks of the May 12 earthquake still stet him shudder.

Jiang Zhongjuan (center) and his fellow rangers on a panda survey at Longxi-Hongkou nature reserve in Sichuan Province.

"I remember one of the latest ones very well as a large falling stone almost killed me in Dujiangyan at 10 am on October 16," he says. "I felt the ground suddenly jerking up and down, making it hard to stand. The falling stone, as large as a cooking pot, fell toward my head at great speed while I was measuring the size of a landslide near a mountain at Longchi Park."

Jiang's quick reflexes got him out of harm's way just in time for him to see the huge rock land several centimeters from his feet. There were two further aftershocks later that day, causing Jiang and his colleagues to rush out of their shelter, an abandoned, collapsed house at a village on their monitoring route.

"Three aftershocks a day! I still felt the ground was moving several days later," says Jiang.

That day was the first day rangers had entered Longchi Park at the Longxi-Hongkou nature reserve in Sichuan since the earthquake jolted southwest China nearly six months earlier.

Jiang was part of a field trip collecting first-hand material on how the earthquake affected wildlife and the habitat of giant pandas in the Minshan and Qionglai mountains in Sichuan, the main habitat of giant pandas and one of the world's 25 key biodiversity areas.

Organized by the World Wide Fund for Nature (WWF) and local forestry departments, the two-week field trip was the first survey on the impact of the quake on giant panda habitats in Sichuan.

Aftershocks and mudflows caused by rain had kept people out of the mountains ever since the devastating quake, measuring 8.0 on the Richter scale, killed more than 80,000 people and destroyed tens of thousands of houses.

Despite the several aftershocks, Jiang had been longing for the field survey and experienced a moment of great, albeit brief, joy when he found evidence of giant pandas still living in the wild.

At the Longxi-Hongkou nature reserve, Jiang found fresh giant panda feces in the dense bamboo forest 2,000 m above sea level. He measured the size of the feces, recorded the detailed location and ground situation of the site and collected samples for further lab analysis.

"It was rare to find giant panda traces in the wild even before the earthquake because the animal tries hard to avoid human beings," he says.

The giant panda's three basic living requirements are water, bamboo and flat areas, with slopes of less than 30-40 degrees. The group's chances of finding giant panda traces were quite rare as the panda meeting places were greatly reduced by the disaster, Jiang says.

The pilot survey chose the Qianfoshan and Longxi-Hongkou nature reserves, two heavily damaged panda reserves in Sichuan, to get a general idea of the earthquake's damage on the local ecosystem.

More than 40 rangers and researchers took part, setting up 15 monitoring lines, each stretching 10 to 40 km. Their daily treks, often more than 30 km, made the days long and exhausting but all coped thanks to their years of field experience.

Zhu Yundong, 31, a ranger from Xiaozhaizigou nature reserve in Beichuan county, whose 5-year-old twin boys were killed in the earthquake, went on the trip to help collect evidence of wildlife in the giant panda habitat. Zhu, whose wife is still in hospital with heavy injuries caused by the earthquake, has developed a sharp nose to distinguish wild animal traces.

He discovered dozens of traces of wild animals like leopard cats, musk deer, tufted deer and pheasants.

To compare the wildlife situation before and after the disaster, the survey covered all the former monitoring and patrolling routes in the two nature reserves before the earthquake.

"Wild animal traces including giant pandas' have obviously decreased, compared with before the earthquake," he says.

It is unknown how many wild pandas were killed or injured in the earthquake as no panda corpses have been found in the wild so far, says Prof Ran Jianghong, from the Bioscience Institute of Sichuan University, who also attended the survey.

Wild pandas' innate survival instincts would have alerted them to flee quake-triggered landslides on high ground.

"The earthquake might not have caused direct population loss to the pandas but it would have damaged their habitats and blocked their migration routes, which may affect the animal's breeding in the future," Ran says.