HEFEI -- Eighteen captive-bred Chinese alligators, five males and 13 females, were released into the wild on Sunday in east China's Anhui Province, to boost the population of this endangered species.

It is the largest group of Chinese alligators ever returned to their natural habitat by Anhui Yangtze Alligator National Nature Reserve, bringing the total number of released alligators to 96.

"These alligators have had blood and DNA tests to make sure that they are fit and strong, and to avoid inbreeding," said Wu Rong, head of the administrative bureau of the reserve.

Wu added that all the alligators had been fitted with electronic ID chips, and six also had radio transmitters to help researchers track them in the future.

As the world's largest Chinese alligator breeding base, the reserve began its captive-release program in 2003.

Statistics show that those that have been released have adapted well and have been reproducing since 2008. As of last year, they had laid 158 eggs and successfully incubated 80 in their natural habitat.

Endemic to China, Chinese alligators, also known as Yangtze alligators, live along the middle and lower reaches of the Yangtze River.

Threatened by human activities and habitat shrinkage, there are only about 150 living in the wild that were born in their natural habitat.

The alligators was included on the country's protection list in 1972.