Within the last month and a half, the corpses of 12 endangered finless porpoises, including a pregnant one, have been found around Dongting Lake, Hunan province.

It has triggered worries from experts about the rare species possibly becoming extinct.

Scientists said finless porpoises, which have lived in the Yangtze River and adjacent lakes for more than 20 million years, will become extinct within 15 years. The porpoises are also called "river pigs".

"Apparently the prolonged drought and low water level due to climate change and increasing offshore human activities are reducing the living space for finless porpoises, accelerating its extinction," Wang Kexiong, an expert of the Institute of Hydrobiology under the Chinese Academy of Sciences, told China Daily.

It is the first time he has heard of so many dead porpoises found within such a short period.

Xu Yaping, a journalist from Hunan's Yueyang city who is campaigning to ensure the survival of the species, said when most of the corpses were dissected no food was found in their digestion systems.

Xie Yongjun, an associate professor of animal husbandry at Yueyang Vocational and Technical College, told China Daily the porpoises may have died due to starvation, poisoning or infectious disease.

There were no obvious injuries in the three corpses he dissected, Xie added.

The Yueyang bureau of aquatic products and animal husbandry is also testing the water in Dongting Lake. A report is expected within the week.

Local fishermen are questioning whether water pollution may be the cause of death.

Li Renhong, a fisherman in Dongting Lake, told City Express, a newspaper affiliated to Hangzhou Daily, that water pollution has been severe in recent years, and it was not rare to see dead fish and other aquatic animals.

Dong Lijun, a professor of the Institute of Hydrobiology, said that because porpoises live in families, one member dying could endanger the others.

Although scientists and environment protection organizations have suggested that the Ministry of Agriculture upgrade the conservation level of the finless porpoise, it remains a Grade 2.

Scientists estimate the number of Yangtze finless porpoises has decreased to 1,000 - less than giant pandas.

That is down from about 2,700 in 1991, according to the Institute of Hydrobiology.

Contact the writer at wangqian@chinadaily.com.cn