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

Abstract

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 5-1 1 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. INTRODUCTIONHumane standards for long-term maintenance of captive chimpanzees (Pan troglodytes) require social housing [USDA, 1985;Prince et al., 1989; Raub, 19921. Multimale groups are a practical solution to the social housing of the captive chimpanzee population, a little over half of which is male [Seal and Flesness, 19861. In addition, if more naturalistic social groupings are desirable in zoos to promote appropriate visitor education, then multimale groups are preferable because the chimpanzee natural social organization is a multimale community [Goodall, 1986; Nishida, 19901. However, both wild and captive adult males have killed other adult males and infants in intercommunity conflicts and intragroup aggression [Goodall, 1977[Goodall, , 1986 de Waal 1986; Nishida, 19901. The University of Texas M.D. Anderson Cancer Center Science Park (UTSP) has maintained multimale groups in its chimpanzee colony for 14 years. Although no deaths of chimpanzees have occurred in the colony as the direct result of adult male aggression, potentially life-threatening wounding aggression has occurred, and aggression has been unacceptably high in some groups. Colony records we...

Space to choose: network analysis of social preferences in a captive chimpanzee community, and implications for management

“…The SNA techniques in this study could have real implications for future introductions. Chimpanzee introductions are difficult in zoos [Alford et al, 1995;Brent et al, 1997]. Using SNA, an individual could be artificially ''removed'' from its home group, and their subsequent effects on social structure could be predicted, before they physically move between zoos.…”

Factors affecting wounding aggression in a colony of captive chimpanzees (Pan troglodytes)

“…These records included the results from routine physical examinations as well as all injuries and health problems that required Alford et al [1995], only wounds that required veterinarian intervention were included in the database. Wounds were categorized as severe if they required medical treatment, which included the prescription of antibiotics and/or analgesics, or surgical treatment (i.e.…”

“…Attempting to further lower the levels of aggression while approximating wild social conditions is difficult. A number of studies have demonstrated factors that appear to increase aggression in captivity, including: (1) the age and sex of the individual [Alford et al, 1995;Baker et al, 2000], (2) the age and sex composition of the group [Alford et al, 1995], (3) the duration of stable group membership [Bloomsmith et al, 1992;Jensvold et al, 2005], (4) the presence of females with maximally tumescent sexual swellings [Bloomsmith et al, 1992], (5) the level of human activity within the colony [Lambeth et al, 1997;Jensvold et al, 2005], and (6) the presence of unfamiliar humans in the colony [Maki et al, 1987].…”

Effects of human activity on chimpanzee wounding

“…Therefore, each subject contributed a mean of 4.7 years of data to this study. This same wounding database was also used in preparing portions of a previous report [Alford et al, 1995], which can be referred to for more details concerning group formation strategies, subject histories, and wound therapy.…”

“…Captive chimpanzees probably engage in more aggression than their freeranging counterparts [van Hooff, 1974;Wilson and Wilson, 1968], and a large number of contexts have been identified which may elicit agonistic encounters. These include introductions of unfamiliar animals [Alford et al 1995;Wilson and Wilson, 1968], reunions between familiar animals [Alford et al, 1995;Bygott, 1979;Goodall, 1986;de Waal and Hoekstra, 1980], interventions on behalf of youngsters in conflicts [Goodall, 1986;de Waal and Hoekstra, 1980], redirected aggression resulting from "frustrating" situations [Goodall, 1986;de Waal and Hoekstra, 1980], arousal during feeding [Bloomsmith et al, 1994;Bygott, 1979;Goodall, 1986;Wrangham, 1974], and competition for access to sexually receptive females [Hasegawa et al, 1990;Rumbaugh et al, 1989;de Waal and Hoekstra, 1980].…”