In 1990, aged just 22, Tang Yulin fulfilled his dream of becoming a third-generation forest ranger in the reserve. In the initial years of his work, the reserve lacked electricity, and the rugged mountain terrain made patrols physically demanding. Rising at 3:30 am every day, Tang Yulin would prepare his meals in darkness before heading up the mountains at 4 am to observe and document the activities and habits of the golden snub-nosed monkeys before they awoke.

Spending nearly 200 days and nights in the mountains each year, Tang Yulin and his colleagues often had to improvise shelters when unable to descend the same day. Through years of observation and learning, he became an expert on the reserve's flora and fauna, serving as a valuable resource for researchers working in the area.