There are many number of reasons for forest patrol teams in Hunchun, Jilin province, to enjoy their work. But what excites them most is finding animal feces — especially from big cats.

An Jianwu's team of 10 rangers is responsible for wildlife conservation in the Yangpao conservation zone, part of the Northeast China Tiger and Leopard National Park in Jilin and Heilongjiang provinces under the supervision of the Hunchun Forestry Bureau.

Walking an average of 10 kilometers a day, the team's main duties are to set up and maintain infrared cameras, find and record the tracks of wild animals — especially endangered species — and remove the traps placed by poachers.

But it's the feces that make their day. They're a sort of communication code between man and nature.

"Feces are special signals sent by wild animals to rangers," said the 38-year-old An, deputy director of Yangpao Conservation Station. "They may contain the genetics, age, gender, physical condition and other information."

He is especially interested in Siberian tigers and Amur leopards, which "have high scientific research value".

The rangers in Yangpao oversee more than 23,000 hectares of forest. To avoid disturbing the animals, they usually set out at 8 am and return at about 3 pm.

"In the northeast, it is really cold in winter and snow can sometimes reach to our knees," An said. "However, it can make it easier to see the tracks of wild animals, including their feces and footprints."

After retirement from the military in 2005, An returned to his hometown and became a ranger.

"At the beginning, it was difficult for me to distinguish the different feces of animals," he said. "Every year, the bureau held training courses for us, and we have learned a lot from the forestry experts."

Years of field work have brought abundant practical experience. "Taking Siberian tigers as an example, their feces always contain the hair of their prey," he said.

The Northeast China Tiger and Leopard National Park, which spans an area of over 1.4 million hectares in Jilin and Heilongjiang provinces, is the most important habitat and breeding area for wild Siberian tigers and Amur leopards in China.

The latest data from the park shows that there are more than 50 of the tigers and about 60 of the leopards, including more than 17 cubs, in the park.

The survival rate of Siberian tiger cubs has increased from 33 percent before the establishment of the park in 2016 to the current 50 percent.