The Chinese Alligator National Nature Reserve in Xuancheng, Anhui province, started its winter hibernation work on Sunday.

The reserve, home to more than 10,000 artificially bred alligators, finished the construction of artificial caves in the alligators' regular living pools this year, in a project costing 16.15 million yuan ($2.27 million), which began in 2021.

The caves not only allow for temperature and humidity control but also enable real-time monitoring of the alligators' condition, providing them with a more comfortable hibernation solution.

The reserve said some alligators have already crawled into the artificial caves to hibernate.

About 2,000 alligators will spend winter in the artificial caves and 2,000 others are expected to be transferred to wintering houses this week. The rest dig their own holes for wintering.

Zhang Song, deputy director of the reserve's administration, said: "Wild Chinese alligators dig their own holes for hibernation. However, in the Chinese Alligator National Nature Reserve, there are currently over 10,000 artificially bred alligators who do not have enough space in the pools to dig their own holes. Therefore, every winter, the reserve carries out the migration work by manually moving them indoors for hibernation."

The Chinese alligator is a rare species found only in China that was classified as a first-class key protected wild animal by the State in 1972.It is classified as critically endangered on the International Union for Conservation of Nature Red List, making it one of the most endangered of the world's 24 crocodilian species.

A cold-blooded amphibious reptile, the Chinese alligator gradually enters hibernation around December and starts waking up in April.

In the late 1970s, there were less than 500 wild Chinese alligators in the world, all living in southeastern Anhui and neighboring parts of Zhejiang province.

After 40 years of protection and development, the wild Chinese alligator population is now estimated to be around 1,200.

Five years of large-scale wild release operations by the reserve have seen 1,500 alligators released into the wild since 2019, playing an important role in increasing the population and optimizing the gender balance in the wild.

The work of transferring alligators to the wintering houses is carried out in different areas and batches, based on temperature conditions. Alligators go into hibernation at 8 C to 12 C, and the temperature in the wintering houses is kept at 10 C.

"After the staff haul the alligators out of the pool, they will clean off the dirt and disinfect them before placing them in the artificial wintering pool," Zhang said. "This ensures that the alligators in the hibernation houses do not infect each other. During the hibernation period, the alligators stop eating and only drink a small amount of water."

The staff regularly clean the wintering houses, spray water to increase humidity, carry out regular disinfection, inspect the hibernation situation, and carefully care for the alligators to ensure they get through winter safely.

Zhang said the establishment of the on-site wintering caves meant fewer alligators would need to be transferred to wintering houses this year. It would also enable targeted monitoring and behavioral observation, improve their wintering environment, and make winter catch-and-release work safer.