Female Contributions to the Peaceful Nature of Bonobo Society
(Pan troglodytes) and bonobos (Pan paniscus) are closely
related, females of the two species show surprisingly large differences in many behavioral
aspects. While female chimpanzees tend to range alone or in small parties during
non-estrous periods, female bonobos aggregate even more often than do males.
Female chimpanzees do not have frequent social interactions with other females,
whereas female bonobos maintain close social associations with one another.
Although the ranging patterns of chimpanzee parties are generally led by males,
female bonobos often take the initiative in ranging behavior. While female chimpanzees
usually do not exhibit estrus during postpartum amenorrhea or pregnancy,
female bonobos exhibit a prolonged pseudo-estrus during such non-conceptive periods.
Studies of these two species have also shown great differences in agonistic
behaviors performed by males. Male chimpanzees frequently fight with other males to
compete for estrous females, but male bonobos seldom do so. While there are many
records of infanticide by male chimpanzees, there is no confirmed record of such an
event among bonobos. Several cases of within-group killing among adult male chimpanzees
have been reported, but there is no such record for bonobos. While intergroup
conflicts among chimpanzees sometimes involve killing members of the other
group, intergroup conflicts among bonobos are considerably more moderate. In some
cases, bonobos from two different groups may even range together for several days
while engaging in various peaceful interactions. I will address two important questions
that arise from these comparisons, exploring why females of such closely related species
show such clear differences in behavior and whether or not the behavioral characteristics
of female bonobos contribute to the peaceful nature of bonobo society.
Evolutionary Anthropology 20:131–142 (2011)OCT/3/2011
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