The research was conducted on Western gorillas in the Gabonese Republic, bonobos in the Democratic Republic of Congo, and chimpanzees in Republic of Uganda, under the human-dominant landscape, mainly for their habitat uses and food selections. These African great apes are regarded as representatives of the primeval tropical forests. However, in reality, they depend largely on the fruits and leaves of pioneer plants or terrestrial herbs which are characteristic of secondary forests. The functional traits of the leaves of the tree species were examined, and we found that tree species in the secondary forest have the higher protein and the lower tannin content than those in the primary forest. These functional traits of the leaves are the desirable properties as a food of wild primates.
