China's White Dolphin

An recent expedition searching for the rare Yangtze River dolphin (pictured right) ended without a single sighting and with the team's leader saying one of the world's oldest species was effectively extinct.

The white dolphin known as baiji, shy and nearly blind, dates back some 20 million years. Its disappearance is believed to be the first time in 50 years that a large aquatic mammal has been driven to extinction.

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. Around 400 baiji were believed to be living in the Yangtze in the 1980s. The last full-fledged search, in 1997, yielded 13 confirmed sightings, and a fisherman claimed to have seen a baiji in 2004. At least 20 to 25 baiji would now be needed to give the species a chance to survive.

The expedition also surveyed another dwindling species, the Yangtze finless porpoise (pictured right), finding less than 400 of them. The finless porpoises are declining at an alarming rate, and are also at risk of extinction.