For August Pfluger and his team, the only time they felt relaxed was during dinner. Pfluger, the Swiss co-leader of a Chinese-foreign expedition searching for the rare Yangtze River dolphin, which kicked off on November 6, usually handed out Budweiser beers to each member of the expedition team. But most of the time, the group worked like robots, standing on the decks of their ships for hours with their eyes glued to binoculars focused on the surface of the Yangtze, the longest river in China.

The expedition, which lasted one and a half month, was searching for evidence of the rare white Yangtze River dolphin, shy and nearly blind, which dates back some 20 million years. It was led by the Ministry of Agriculture and brought together world-class experts from institutes such as the Swiss Federal Institute of Aquatic Science and Technology, the National Oceanic and Atmospheric Administration (NOAA), the Hubbs-Seaworld Institute from San Diego and the Fisheries Research Agency in Japan.

For nearly six weeks Pfluger's team of 30 scientists scoured a 1,000-mile heavily trafficked stretch of the Yangtze, where the baiji once thrived. The expedition boats were equipped with high-tech binoculars and underwater microphones.

But the search was in vain: not a single baiji was sighted. A few baiji may still exist in their native Yangtze habitat in eastern China but not in sufficient numbers to breed and ward off extinction, said Pfluger.

"We have to accept the fact, that the baiji is functionally extinct. We lost the race," Pfluger said in a statement released by the expedition. "It is a tragedy, a loss not only for China, but for the entire world. We are all incredibly sad."

"It's a tremendously sad day when any species becomes extinct. It becomes more of a public tragedy to lose a large, charismatic species like the river dolphin," said Chris Williams, manager of river basin conservation for the World Wildlife Fund in Washington, D.C.

Randall Reeves, Chairman of the Swiss-based World Conservation Union's Cetacean Specialist Group, who took part in the Yangtze mission, said expedition participants were surprised at how quickly the dolphins had disappeared.

"Some of us didn't want to believe that this would really happen, especially so quickly," he said. "This particular species is the only living representative of a whole family of mammals. This is the end of a whole branch of evolution."

But Wang Ding, a Chinese hydrobiologist and co-leader of the expedition, declined to say that the animal was already gone from the earth. "Finding no trace of the baiji doesn't necessarily mean that the animal is extinct. We might have missed observing them during the night, and our expedition only searched on the main stream of the Yangtze but didn't cover its branches," he explained.

The rescue

The disappearance of the baiji, dubbed the "goddess of the Yangtze," symbolizes how unbridled economic growth is changing the country's environment irreparably, some environmentalists said.