He took the job at the Zoige Wetland National Nature Reserve in 2008. Reserve officials had tried to recruit many local residents as rangers, but the work was too hard, with long patrols at more than 3,400 metres and freezing winds all winter. One by one, the others left. Ruoke stayed.
His colleagues call him the "midwife". During breeding season he guards the nests. One pair of cranes he first met at dawn near his patrol station. Two years later they nested at Flower Lake, and he went back to the nest again and again to keep predators away from the chicks. The next spring the pair returned to his station and brought their young with them.
His family joined the work too. His wife, Namoje, gave up her job in a nearby town to support it. Their son, Renqing Duoji, has since taken over from his father as a ranger. At 37 he found three crane pairs on a single patrol, and he said everything he knew about the birds came from watching his father.
This ground has a history. The reserve covers the old Songpan Grassland, the marshland that Red Army soldiers struggled across during the Long March. In 1935 the Right Column spent about seven days crossing it in the rainy season. China News Service published Ruoke's story to mark the march's 90th anniversary.
Today the marsh is being refilled on purpose. Small dams across the reserve slow the water and keep it in the peat. At Flower Lake the water has risen by 52 centimetres, and the lake has spread to three times its former size. The black-necked crane, the only crane that lives and breeds on high plateaus, has more than doubled in number here. Other rare birds have started to arrive as well: oriental white storks, and crested ibises, a species once reduced to seven known wild birds.
Sorang Duoji, the reserve's research director, measures success simply. Whether the wildlife is present is what tells you the state of the environment.
By that measure, every spring brings good news. The cranes come back through the mist, and a Tibetan ranger is waiting for them. Now it is sometimes the son.