Most of the pandas' favorite arrow bamboo in a 350,000 square-kilometer (217,000 square-mile) region of Sichuan province is going through a once-in-60-year cycle of flowering and dying before regenerating, said Yang Xuyu, deputy head of the province's Wild Animal Preservation Station.
The pandas are moving to other areas of Sichuan, which has about 40 reserves of various sizes.
"No wild panda has been found dead of starvation," said Yang. But more than 80 percent of bamboo in the affected region, called Ruoergai, is now unfit for the animals to eat, he said. Pandas will not touch the plant once it flowers.
About 1,200 pandas - 80 percent of the surviving wild population in China - live in several mountainous areas of Sichuan.
Hundreds of pandas died of starvation in Sichuan in the 1980s when arrow bamboo in some reserves flowered and then died.
Pandas derive most of their nutrition from arrow bamboo and can starve once the plant enters its dying-off stage. The bamboo produces seeds before dying, and takes 10 to 20 years to grow back.
Yang told a conference on panda survival in Chengdu, Sichuan, on Sunday that a shrinking habitat due to farming and industrial development makes it increasingly hard for the animals in the wild to find food during the bamboo life cycle, according to the Xinhua News Agency.
China's forestry bureau is carrying out a panda rescue drive and working with the World Wildlife Fund to try to restore panda migration paths, Xinhua said.
Also Monday, Xinhua reported that a record 12 pairs of panda twins were born in captivity this year, thanks to a maturation of artificial breeding techniques that China first began exploring in the 1960s, according to Zhang Zhihe, head of China's Giant Panda Breeding Technology Commission.
A total of 31 pandas were born this year. Last year, 33 were born, including 11 pairs of twins, Xinhua said.