The Vertical Commute
In the dense bamboo forests and high alpine meadows of China's Wolong Nature Reserve, the Sichuan takin (Budorcas taxicolor tibetana) undertakes a massive seasonal migration. This is not a horizontal journey across plains, climbing and descending thousands of meters on the steep mountain slopes they live on. For years, scientists assumed this migration was driven by temperature and snow cover, a pattern for mountain animals. Research using GPS collars on the takin has uncovered a different motivation for their travels. It appears their movements are synchronized not with the thermometer, but with the life cycle of bamboo.
The takin, a stocky bovid called a "goat-antelope," shares its habitat with the giant panda. Both species rely heavily on bamboo. Each spring, takin herds of up to 300 individuals move up the mountains, reaching elevations above 4,300 meters (14,000 feet). As winter approaches and food becomes less available, they descend into the forested valleys in smaller groups of 10 to 35. This elevational migration follows well-worn paths that the animals use year after year. The GPS tracking data revealed that this vertical commute aligns with the availability of fresh bamboo shoots and leaves at different altitudes, a more important resource than seeking warmer ground. They follow the green wave of new growth up the mountains in spring and retreat down as the high-altitude vegetation dies back.