CHONGQING, April 14 (Xinhua) -- Two Francois' leaf monkey cubs, one of which is in the process of changing its fur color, were spotted and caught on camera in a nature reserve in southwest China's Chongqing Municipality, the reserve said.

Li Bin, a local television reporter, captured the endangered monkeys earlier this month at the national nature reserve of the Jinfo Mountain.

In the video provided to Xinhua, one of the cubs with the orange crown was trying to get out of her mother's arms and learn how to climb.

The other little monkey, which has turned into entirely black, was jumping up and down on the treetops.

Shen Ling, a senior engineer of the nature reserve administration, said Francois' leaf monkey cubs will go through a fur color change period from orange to black while growing.

"Through the footage, we can see the tail and part of the body of the langur have turned black, while the top of the head is still orange, indicating that the color change is a process from bottom to top," Shen said.

Francois' leaf monkeys are usually born at the end of the winter, and March and April are a critical period for their growth.

"This footage also tells us that during this period, we should strengthen the monitoring and protection of them," she said.

Also known as Francois' langurs, the species is one of China's most endangered wild animals and an endangered species on the International Union for Conservation of Nature red list. They are found in China's Guangxi, Guizhou and Chongqing as well as the northern mountain areas of Vietnam.

The adult Francois' langurs have a black body, measuring 60 to 80 cm long, and weigh 6 to 8 kg. There are about 2,000 Francois' leaf monkeys worldwide, of which 1,500 live in China.

The latest survey in 2015 showed the number of Francois langur was 151 in the reserve, which increased significantly compared with 70 in the 1990s and 140 in 2004.