National Geographic with news that Asia's critically endangered Irrawaddy river dolphin may closer to extinction than scientists previously thought.

According to Touch Seang Tana, chair of Cambodia's Commission for Mekong Dolphin Conservation, there are now about 160 dolphins in the upper Mekong River, up from only 90 when the Cambodian government banned the practice of net fishing last year.

But researchers who study the rare dolphin have expressed deep skepticism that such a dramatic turnaround could have occurred.

They said it would be biologically impossible for the dolphins to rebound so quickly, because their gestation period is 11 months and the animals generally only have one offspring every two years.