Wounding aggression during the formation and maintenance of captive,multimale chimpanzee groups

Although the multimale community is the natural social organization of chimpanzees, both wild and captive adult males have killed other adult males and infants in intercommunity conflicts and intragroup aggression. Despite the potential for serious aggression, the formation of captive, multimale social groups is desirable for the efficient, long-term, humane housing of chimpanzees in socially and physically enriched environments and for the education of zoo visitors. The University of Texas Science Park (UTSP) has maintained multimale groups of chimpanzees for 14 years. In the UTSP outdoor corral housing, multimale/multifemale social groups of unrelated adult and adolescent chimpanzees (42 F, 46 M) were formed by a series of 397 individual introductions. Wounding aggression was minimal during introductions of females to males or other females and upon male-male introductions of formerly single-caged adolescent and young adult males having had long-term prior visual familiarity. Serious wounding occurred during male-male introductions when there were major discrepancies in the age and social experience of the subjects or when adult, socially experienced males were reintroduced to former group mates following lengthy separations. Male wounding in the eight established long-term groups of 5–11 adults (2–7 males) averaged 1.4 episodes per male-year of residence; 14% of male wounding episodes required surgical therapy. Adult wounding was significantly associated with the presence of one or more group females with maximally tumescent genital swellings. No male-perpetrated infanticides occurred. Not all multimale groupings are successful, but the majority of formerly laboratory-housed chimpanzees may live and reproduce safely in multimale groups. Experience with all-male groups at UTSP suggests that bachelor groups are also practical for long-term housing. © 1995 Wiley-Liss, Inc.