抄録
Social interactions of the second ranking male chimpanzee, Nsaba, were analyzed at M group of the Mahale Mountains National Park, Tanzania, comparing with those of a middle ranking male, Aji, who was as old as Nsaba. Both Nsaba and Aji spent more time in proximity to and grooming with adult males than individuals of any other age/sex classes. As a whole, they engaged in grooming reciprocally with adult males, groomed adult females more than were groomed by, and groomed adolescent males less than were groomed by. However, Nsaba almost onesidedly groomed some adult males, while Aji engaged in grooming reciprocally with most adult males. They were frequently pant-grunted at by adolescent males and adult females. They uttered about 2 pant-hoots an hour, some of which were followed by aggressive displays.
Nsaba had a strained relationship with the alpha male Ntologi. Although he sometimes pant-grunted at and followed Ntologi, they did not groom one another. Furthermore, Ntologi performed aggressive displays at Nsaba, especially when he stayed together with Kalunde, the third ranking male. Nsaba sometimes traveled alone, avoiding Ntologi's aggression. Ntologi seemed to have tried to form coalition with Kalunde and opposing him against Nsaba. However, Kalunde frequently engaged in grooming with Nsaba when Ntologi did not stay nearby. Coalition strategies among males were discussed, focusing on the second ranking male.
