In 2018, researchers from the Chinese Academy of Sciences' Kunming Institute of Zoology visited the area and launched a comprehensive survey of the leaf monkeys.

Huang and Wang were hired by a graduate student at the institute to help him track the monkeys during his survey. He also lived in their house during his field survey.

"Every month he would come and work with us for 18 days," Wang said.

The local volunteers learned from the researchers that monkeys were a species under first-level State protection. They also discovered the forest, comprising part of the State-owned Mangxing Forest Farm and part of the collective forest belonging to villagers living in Xuangang township in Mangshi, was home to China's largest known population of the species.

"We were told that about 320 leaf monkeys in five families were living in our forest," Huang said.

In 2016, the prefecture's forest and grassland bureau hired Huang as a patrolman to protect the collective forest. The target of his protection has since become the langurs.

It can be challenging work. From December to mid-June, he needs to patrol the forest almost every day, tracking the monkeys' movements and eliminating any forest fire hazards. An average patrol route is 6 kilometers, and a longer one of more than 10 km will put him on a mountain path for the whole day.

"June 15 marks the beginning of the rainy season," Huang said. "In the following months, I can relax a little bit and decrease the frequency of my patrols."

While the work offered an allowance of 1,800 yuan ($250) a month, that is not the reason for his persistence, especially as the local government's budget woes meant it failed to pay him for the past two years.

However, his work has brought guests — photography enthusiasts — to the family.

"People come for our help to find the monkeys," Huang said. "Because of my work, more than 80 percent of them prefer our service to the others."