The social group of pygmy chimpanzees (Pan paniscus) of Wamba

This is a sociological study of the pygmy chimpanzees of Wamba which have been provisioned sufficiently since 1977. The society of the pygmy chimpanzee is basically similar to that of the common chimpanzee in the flexibility in forming parties and in the existence of a definite social unit, i.e.,unit group. It also resembles in that young females play an important role in exchanging members among unit groups, thus, as transmitters of genes from group to group, while males do in integrating groups, delimiting the social boundaries of unit groups through their inter-group antagonism. Pygmy chimpanzees differ from common chimpanzees in fission and fusion pattern of parties. The former generally forms parties larger in size and more homogeneous in composition than the latter. Any party of the former has both reproductive and nursing functions, while the parties of the latter are categorized into various types according to functions and compositions. This uniformity in pygmy chimpanzee parties seems to be well maintained by the females' high sexual ability to manifest semi-continual estrus.