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Primate Research Institute, Kyoto University
Variation in Intergroup Relationships Among Species and Among and Within Local Populations of African Apes
Although many animals typically defend key resources from conspecifics during encounters, tolerant encounters also occur frequently in some primate species. For example, African apes and humans (Homininae) show large variation in terms of agonistic and affiliative intergroup relationships, and local human communities are formed via a network of affiliative relationships among groups. To understand this variation and its evolution, we need to examine the variation between species, between populations, and within populations. In the genus Pan, both eastern and western chimpanzees commonly express aggressive intergroup relationships, whereas intergroup relationships in bonobos are generally affiliative. In the genus Gorilla, although the proportions of groups with multiple males differ, all subspecies show large overlap of home ranges and both aggressive and affiliative intergroup interactions.
Differences in intergroup relationships among local populations of the same (sub)species are limited in both Pan and Gorilla. In contrast, intergroup relationships vary within the same local populations in bonobos, with female dispersal among groups seemingly contributing to the affiliative relationships. Such tendencies in bonobos seem to resemble those in local human communities, where intergroup relationships differ for different combinations of groups and female dispersal among groups plays an important role in affiliative relationships. Intergroup relationships within the same local populations also vary from affiliative to aggressive in all subspecies of gorillas, and kin relations between leading males play important roles in affiliative relationships. Studies of variation in intergroup relationships, the contributions of males and females to such variation, and the genetic structure of local populations might increase our understanding of the evolutionary process underpinning local communities in Homininae.c
International Journal of Primatology:
2020/04/06 Primate Research Institute