Although there are no developed roads in the protected area, it still does not stop people from sneaking in. "A momentary lapse can allow people to slip in unnoticed," he adds.

The checkpoint is near Chongqing and during summer, many people arrive to escape the heat. There is an iron gate that cannot fully block the riverbanks. During the non-flood season, it is possible to walk along the shallow riverbeds deep into the core protected area.

The couple can't relax for a moment from dawn until midnight. There are some people who, when told this is a core protection area and entry is prohibited, will leave, but there are a few, who don't respect the rules. The ecosystem is frail here and is home to many endangered species. They must report any trespassing to the management station and make sure they escort those people out.

Some people also enter through mountain trails for fishing or hiking. This is why patrols cannot be interrupted for even a moment. Along the way, if they find such individuals, they must persuade them to turn back. This is not only to protect the plant and animal habitat but also to ensure the visitors' safety.

Loneliness is inevitable. The network connection at the checkpoint is very weak and the core of the protected area is isolated. During their daily three-hour patrols, they never know what kind of wildlife they will encounter that could put their lives at risk. However, intriguing occurrences help the couple confront the solitude.

"Observing the changes along our path makes time pass easily. You can find many subtle changes day by day," Zhao remarks. "For instance, if you find the bush collapsed in a section, it means wild boars were there looking for food. In winter, we feed the macaques regularly. Every time we clang the bowls, they flock to us. If we forget to give them food on time, they shake the branches angrily, like little kids."

To feed the macaques, Sheng prepares peanuts, corn and walnuts. She cracks the nuts carefully to make them easier to eat.

In 2003, Zhao's father, a former village cadre, assumed the role of station chief for an artificial ecological public welfare forest construction project within the reserve. Leveraging his local influence, he mobilized nearby villagers to partake in tree planting and protection efforts. Within a year, 15,000 mu of forest were planted, laying the groundwork for a substantial increase in forest coverage.

In 2005, Zhao succeeded his father in this position, dedicating himself to guarding the area and embracing the forest as his home, following in his father's footsteps.

Through their hard work generation by generation, the forest coverage of Dashahe Nature Reserve has significantly increased from 61.79 percent in 2002 to 84.67 percent in 2024. Currently, the reserve is home to 27 groups of Tonkin langur, totaling 166 individuals.

With improvements to the ecological environment, the population of wild macaques is also steadily increasing, with over 1,200 macaques now residing within the reserve. Behind these numbers is the hard work and unwavering dedication of the forest rangers.

Having known each other since their early teens while living in the same village, Zhao and Sheng built a family and raised two daughters. Their elder daughter works in Sichuan province while the younger daughter attends high school. During Spring Festival, their daughters visit the checkpoint for a family reunion, bringing food specialties and more to mark the occasion and celebrate the coming New Year.

"Maybe the station is not as good as the house in the village, but once our family is together, happiness fills every corner of the checkpoint," Sheng says.

Zhao Yandi contributed to this story.