Through the mist of Southwest China's Gaoligong Mountains, our camera follows a solitary figure into the forest. This is the home of the Skywalker hoolock gibbon, one of the world's rarest primates, with fewer than 200 remaining in the wild in China.

For 17 years, ranger Yang Youshan has walked these trails. The camera captures his monthly five-day treks tracking an aging gibbon couple, documenting the numbered food trees and sleeping sites that map their territory. It's a quiet ritual of attentiveness between man and gibbon.

In 2005, a colleague captured the first clear photograph of this species here. Twelve years later, Chinese scientists named it the Skywalker hoolock gibbon, marking the first gibbon species named by Chinese scientists in a century.

This video tells a story of understated devotion: one man, one mountain, two gibbons, 17 years.