The utilization of caves is a rather rare phenomenon in nonhuman primates, found almost exclusively in those members of the genus Trachypithecus
that share a preference for forest on limestone (karst) hills in Vietnam and southern China. Here we report a new case of usage of caves as overnight sleeping shelters by François' or black langurs ( Trachypithecus françoisi
) at Mayanghe National Nature Reserve in Yanhe County, Guizhou Province, China. We tentatively address three possible hypotheses that may account for the use of caves in François' langurs at Mayanghe: shelter against climatic conditions, acquisition of minerals and protection from predators.