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Chimpanzees

About Chimpanzees

Chimp Behaviour

Social Organization

 

Chimpanzees are highly social beings, just like humans. Social interactions are essential in a chimpanzee’s development, learning and overall wellbeing.

 

Learn more about the social organization of chimpanzees:

 


Groups and Communities

Chimpanzees live in social groups called communities or unit groups. At Gombe, the number of individuals in the main study community, Kasakela, has ranged between 40 and 60 since 1960. Communities may be smaller or larger in other areas.

Chimpanzees' social structure can be categorized as "fusion-fission." This means they travel around in small subgroups of up to 10 chimps, the membership of which is always changing as individuals wander off on their own or join other groups. At times many of a community's members come together in large excited gatherings, usually when fruit is available in one part of the range, or when a sexually popular female comes into oestrus (period of female sexual receptivity).

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Family Bonds

 

Individuals may switch groups on occasion, but close, supportive, affectionate bonds also develop between family members and other individuals within a community, that can last a lifetime. Chimpanzee family bonds are very strong, especially mother-daughter bonds. Mothers and dependent young up to age seven or so are always together. Some individuals travel together more often than others—such as siblings and pairs of male friends. Contact is maintained between members of the scattered groups by means of the distance call: the pant hoot.

Females disperse from the natal group once they are mature and spend most of their time alone, with dependent offspring. Males usually remain in natal groups, cooperate in defense of the community range, and spend long periods of time in proximity to other males. Males will sometimes form coalitions with each other to support each other during conflicts with other groups.

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Dominance Hierarchies & Mating

Within a chimp community, a male hierarchy, ordered more or less in linear fashion, establishes social standing, with one male at the top or "alpha" position. All adult males dominate all females, although females have their own hierarchy, albeit much less straightforward.

Age is a deciding factor in male dominance hierarchies - the alpha-male is usually between the age of 20 and 26. Other factors that determine dominance and social status are physical fitness, aggressiveness, skill at fighting, ability to form coalitions, intelligence, and other personality traits. Status is either maintained or changed through communication and social interactions, such as physical competition and grooming.

The males of a community regularly patrol their boundaries, and if they encounter individuals of a neighbouring community they may attack with extreme brutality. The only individuals who can move freely between communities are adolescent females who have not yet given birth. They may transfer to a new community permanently or, having become pregnant, move back to their own birth group.

There are several mating patterns seen in chimps. Some females in oestrus (period of sexual receptivity) are more attractive than others. A popular female may be accompanied by many or all the adult males of her community, with adolescents and juveniles tagging along. Or, the dominant male of the group may show possessive behaviour toward her, trying to prevent other males from mating with her. A third mating pattern is a consortship, during which a male persuades a female to accompany him to a peripheral part of the community range. If he can keep her there until the time of ovulation, he has a good chance of siring her child. Even low-ranking males can become fathers in this way, if they have the skill to lead a female away during her fertile period of her reproductive cycle.

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Warfare and Violence

Since there is a hierarchy system in chimp societies, most disputes within a community can be solved by threats rather than actual attacks. They use gestures and postures to indicate threat, such as: tipping the head, making hitting gestures, flapping hands in the air, swaying branches, throwing objects, and charging towards another. These gestures are often combined with vocalizations.

Chimpanzees are however, capable of physical violence. In 1974, Dr. Jane observed a 4 year territory war between two groups of chimps that ended with one group killing all of the other chimps in the other group. This was the first recorded account of non-human primate warfare.

Infanticide also occurs within chimp communities. Male chimps sometimes kill infant chimpanzees, for a variety of proposed reasons, but it is most commonly thought to promote the female who he is mating with, to wean his offspring sooner and to ensure that the offspring is his.

 

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