Carrying her telescope, Guo's colleague Wang Libin makes between one and four circuits of the park, each around 2.5 kilometers. It is the job of Wang and two others to "guard" the milu and closely observe the health conditions of the wildlife in the park, especially the deer.

"We take care of them just like caring for our own children. We are often concerned about their diet and nutrition," Wang explains.

By counting and recording the animals every day, Wang maintains a clear picture about all the migratory birds and animals that are residing in the park at any given time.

According to Wang, a healthy wetland ecosystem needs biodiversity, and the milu serves as a flagship species for the area's ecosystem.

"It is unusual to have such a large section of wetland in a Beijing suburb, a city with a population of more than 20 million, dedicated to the protection of wildlife, especially the milu," Guo says.

According to Guo, the local district government in Daxing has gone to great efforts to enhance the environment in the reserve to make it a suitable habitat for the milu. Pollution in the surrounding areas, which was a serious problem threatening the milu in the early years, has been successfully tackled.

Guo, who started working at the Nanhaizi Milu Park in 1998, says he immediately fell in love with the milu and was touched by its unusual story.

Guo's daily routine includes managing the museum and passing on the knowledge he has built up about the milu to visitors. More than 400,000 people visit the park and the museum annually.

"My friends often call me a spokesman for the milu, and I'm happy to take on that role," explains Guo, 57.

"As someone who is involved in popularizing science, I feel so lucky to be able to learn about the milu and work to raise awareness about them."

According to Guo, the general public still has a limited knowledge of both the milu and Naihaizi.

In Guo's opinion, the fate of the milu is one that is closely related to the ups and downs of the nation.

Forced to live far away from home for a century due to the chaos on its native soil, the milu have now witnessed a revival thanks to huge protection efforts at a time marked by stability and fast growth, Guo says.