At 83, George Schaller, has the drive and enthusiasm of a man half his age.

Recognized by many as the world's leading field biologist, Schaller has dedicated five decades to wildlife conservation. He once woke up from a nap to find himself surrounded by a pride of lions in Tanzania; has been stalked by a wolf on the Tibetan Plateau; and was left the dubious "present" of a pile of droppings on his camp bed from a kind Giant Panda -- all in the line of duty.

Schaller is currently on a three-week research mission, with a team of Chinese scientists in northeast China's Qinghai Province, to track and study the shy snow leopard. The largest population of wild snow leopard is found on the Qinghai-Tibet Plateau.@ He is no stranger to this cold, bleak terrain, having been instrumental to much of the region's conservation work over the past 30 years. Unlike perhaps any other octogenarian, rather than balking at the prospect of camping in the snowy mountains, battered by icy winds and gasping for breath in the thin air, Schaller prizes it. In what other setting could he encounter such rare and elusive animals in their natural domain?

"Everything in nature is related," he said.

The snow leopard is the flagship species at Sanjiangyuan (the Three Rivers Nature Reserve), where the headwaters of the Yellow River, the Yangtze and the Mekong flow, eventually providing water for millions of people.

Animal conservation is a trickle-down business. If big animals are protected, then so, too, are thousands of other species, and by association, the water resources will also be protected, Schaller explained to Xinhua.

"You need to show respect, compassion, even love toward all living beings, to make sure they continue to exist."

Since 1959, Schaller has studied wildlife in more than 20 countries. China tops the list. For the past 30 years, he has visited China every year, spending more time here than in his home in Missouri.

In 1980, he became the first Western scientist to visit Sichuan Province after he was invited by World Wildlife Fund (WWF) to study the giant pandas there.

This five year project led to "The Last Panda," a book in which Schaller rejected the practice of keeping pandas in captivity to boost the population.

"It was a little bit difficult." Schaller said when explaining his first wildlife study in China just after the Cultural Revolution. Foreigners were treated with great suspicion at the time, but what concerned him were not prying eyes but ordinary people's ignorance of nature.

"On the Tibetan Plateau, when I talked to locals about animal conservation, and they looked at me blankly. They had no clue what I was talking about!"

However, China has come on in leaps and bounds since the 1980s, and began to release captive-bred pandas into the wild in 2006.

"China has done a pretty good job," Schaller admitted.

He used the momentum from the panda program to draw attention to the plight of another endangered animal, the Tibetan antelope. In 1992, after two year's of study, Schaller lifted the lid on the illegal hunting and smuggling of Tibetan antelope hide to India to be made into Shahtoosh, a shawl woven from the "king's wool," the fine down of the antelope.

On his suggestion, a nature reserve was established along the border between China and India.

Schaller was born in 1933 in Berlin and moved to the United States at very young age. In 1959, as a Ph.D. student, he traveled to Central Africa to live with and study the mountain gorilla. One day, a gorilla climbed down from a tree and sat next to him. It may be the first time a mountain gorilla sat with a human in recorded history.

"Both of us were very nervous", Schaller recalled.

In 1963, he published "The Mountain Gorilla: Ecology and Behavior," which cleared up many misunderstandings of gorillas.

His work brought him international acclaim, and a host of accolades, including the World Wildlife Fund's Gold Medal for "contributions to the understanding and conservation of endangered species".

"Animals are shy. Many have probably never seen people," Schaller explained, adding that danger rarely comes from animals but from people.

In 2005, Schaller went to Iran to study Marco Polo sheep. He tried to persuade a local warlord to protect the animals. The chief was shocked that a gray-haired American had traveled thousands of miles just for some sheep.

Knowing it would be useless to discuss conservation with a warlord, Schaller tried to persuade him to charge a tax on hunting, which would not only protect the sheep, but also help earn money for the clan. Money talks and the warlord took Schaller's advice.

"Protecting animals is not just a job for naturalists, or governments. It is a job for everyone. Everyone must be involved to protect our future."

Schaller's wife and two sons share his interests and he has a committed following of Chinese students and scientists.

"He is very amiable", said He Bing, who worked with Schaller on the snow leopard study. "He is diligent, easy-going and pulls his weight.

"Once out on the plateau, we were all very tired and we asked for a break. Only Dr. Schaller complained; 'We have been in the car for very long time. When shall we climb mountains?'"

Asked when he will stop his work, he replied, "Why stop? I am still young."