The black crested gibbon (Nomascus concolor) is an animal protected as a Class A endangered species at national level in China. In fact, there are only slightly over 1,000 black crested gibbons in the entire world, and over 500 of them live on Wuliang Mountain in Pu'er, where the animals begin to cry as early as the time when the first rays of sunlight hit the valley.

Considering the species' small population and the location of its habitats in dense forests, people rarely see black crested gibbons at close range even in their habitats, and in most cases they can only listen to them cry in the distance. A group of scholars and experts come to the monitoring station here for a stretch of one or two dozen days and cannot hear them cry if they are unlucky.