A case of inter-unit-group encounter in chimpanzees of the mahale mountains

In the Mahale Mountains, Tanzania, a case of encounter between chimpanzees of different unit-groups was observed in June 1979, where two young adult males and two adult females of the M-group came across four adult females and a juvenile male of the K-group. While the participants did not explicitly show any agonistic behavior but greeted and groomed each other, they repeatedly defecated during the interactions. This clearly indicated that they were put under unusual strain, which could be considered to be brought on because they were cognizant of that the opponents were not the members of their own unit-group. It can be said, therefore, that in chimpanzees, even females identify themselves with a particular unit-group, and that a chimpanzee unit-group should be regarded as a bisexual unit.