Survival struggle

Among Yang's bitter memories of his field research is an expedition to the Gaoligong Mountains, which neighbor the Tibet autonomous region, in 2000.

"At the beginning of the eightday expedition, one of my colleagues described the route we were to take as one for hunters," Yang recalled. "The man, however, downgraded it twice as we proceeded. He soon nicknamed it as a path fit only for monkeys, but later sneered it was a mouse trail when we wrapped up the tough journey. He said he would never set foot on it again."

One of the team members sustained a mild injury after they set off, but their guides refused to take him back for treatment. "They (the guides) said those who left their team would die in such an area," Yang said.

Sleeping conditions were perilous. One night they pitched their tents on a slope so steep they were constantly rolling around in their tents.

"One of my colleagues said he wished he could nail himself to the ground so he could feel fixed to something," Yang said.

They took enough food for 14 days, but ran out on the seventh as they ate more than usual due to exhaustion from crossing the harsh terrain.

Along the way they walked on cliff edges, labored up and down mountain slopes with dangerous loose rocks, and traversed slippery rivers and wetlands.

Near exhaustion, they came across a hunter on the eighth day who sold them maize flour so they could complete their expedition and return home.

For Yang, the true indication of how tough the trek had been were the leather hiking boots he bought before the expedition.

The shoe shop owner had given him an assurance about the high quality of the boots, and promised Yang he could exchange them if so much as a scratch appeared on them in the first six months.

"When I went back to him with the shoes he was astonished and asked if I'd hacked them with a saw," Yang said laughing.

Over the eight-day trek he lost 1 kilogram every day, a more serious indication of just how physically demanding the trip had been.

Today, field expeditions have become much easier thanks to better access to roads and highways and use of high-tech instruments such as infrared camera traps.

As a long-term legacy of his journeys, Yang suffers from stomach illnesses and rheumatism, health problems which he manages with medication and proper care.