Inside a Chimpanzee Community

Chimpanzees and humans are both very social species. We both surround ourselves with family members and close companions, even individuals we donít get along with. Although we are similar, the structure of the social interaction of humans and chimpanzees can vary quite significantly.

 

Chimpanzees have a complex social structure called a fission-fusion society. An example of a fission-fusion society you can think of a group of college students residing at a campus. During the day, groups of students have different classes, and may hang out together, scattered on the campus grounds. At night, all of the college residents come back to the dorms to sleep. This is like chimpanzees in that, chimpanzees live in a large community with different subgroups that break apart during the day but come together in a central location at night to sleep. They will disperse themselves in these smaller groups to find food throughout their forest territory. These subgroups will then congregate in their large community and sleep near each other, up in the trees, at night. The subgroups will switch constantly, with different chimps spending time together day to day.  As humans, we do this too. On different days, we may spend time with different groups of friends or family members.

 

A chimpanzee community consists of adult males and females with adolescents offspring. The size of the subgroups can change depending on the chimpanzeesí activity.  For example, a hunting party will have a large number of chimpanzees because it is easier to catch prey with more hunters. Foraging parties also have a large number of individuals when food is plentiful. While traveling from one food source to another, chimpanzees may be in small groups or alone because individuals  travel at different speeds. Even in our lives, the number of individuals we spend time with varies with our day to day activities.

 

Male chimpanzees often spend their entire life in the community they were born in, whereas female chimpanzees may travel to different communities. Males tend to be more social than females and prefer each otherís company but females tend to be less social and spend most of their time with their young. Females tend to find food alone instead of in groups because of food competition. Females need to spend their time taking care of their young and cannot waste energy fighting over food. Male chimpanzees are able to fight over food because they do not take care of the young.

 

Chimpanzee society is dominated by male strength. The adult males of a community will fight for the top ranking position called an alpha male. Usually the alpha male is the strongest chimpanzee in the community but this is not always the case. 

 

Some male chimpanzees are not strong enough to overtake the position as alpha male by physically fighting, so they overtake the position with their smarts. A male chimpanzee can gain support from the other chimpanzees in the community. If enough chimpanzees favor one male over the alpha male, then the community can help the favored male take the position as alpha male. When a male is in the alpha position, he often displays his strength. When his hair sticks straight up we call this  piloerection he does this to make himself look bigger and he runs around making loud shrieking vocalizations. He may break branches off  trees and throw rocks to intimidate the other chimpanzees and help him keep the power he has within the group. Could you imagine throwing a temper tantrum every time you wanted to get everyone to respect you? It would get pretty tiring after a while. Chimpanzees lower in rank than the alpha male will offer their hand while grunting to the alpha male as a sign of submission. The position of alpha male is never permanent and often changes from male to male.

 

Female chimpanzees also have a dominance hierarchy in the group in order to gain first access to food and other resources. Their status is not as extreme as the males. A dominant femaleís offspring will inherit the status  of her mother. Have you ever met someone who was born into a wealthy or highly respected family? Well, that gain of status can be paralleled to this phenomenon in chimpanzees.

 

The male has to be accepted by the females before he can gain his status. Females can be very choosy and if the females do not like approve of the alpha male they will not let him mate with them. Females provide all the care for their offspring and they do not want a male as their leader unless he is the one they feel can best provide for the group. Females can choose to support another male they see being a better leader for the group. So itís important for males to have good relationships with the females of the troupe.

 

Chimpanzees are very territorial. Different communities live in different parts of the rainforest. When a chimpanzee community is on the boundary of their territory conflicts can arise between chimpanzee communities. Mother chimpanzees with babies have to be cautious on the territory edges because often babies will be killed by other chimpanzees from neighboring communities. Aggression usually doesnít occur within the community unless it has to do with fighting for the alpha male position or fighting over females.

 

A female chimpanzee becomes more social when she is ready to mate. Usually when a female is ready to mate when there is food readily available. This benefits the female because the female needs more food to support her baby chimp. The female has 10-12 days available to mate and become pregnant. During these days male chimpanzees may fight over the female. Usually, the alpha male gets the opportunity to mate with the female. A male chimpanzee will shake a branch to invites the female to mate with him. When a female is ready to mate, a male may guard her so no other male can mate with her. After the female is pregnant, the male has nothing to do with the baby or mother. We humans, unlike chimpanzees are monogamous and usually both the male and female will contribute to raising the child.

 

 

Message from CAC'ers

 

When we were in Tanzania, we got the great opportunity to see a fission-fusion society at work.  We spent three days in Mahale and three days at Gombe.  In both places we saw certain recognizable individuals each of the three days we were there.  It was really cool to take note that different individuals were hanging out with each other from day to day.  We even got to see males doing their dominance displays! We sure thought it was intimidating!

 

CAC is a program of the Institute for the Study of Human-Animal Relations at Canisius College in Buffalo, NY.