When Dr. Goodall started her study of chimpanzees in 1960, very little was known about their behavior in the wild. Since then, studies analyzing almost every aspect of chimpanzees’ multifaceted behavior have sprung up across Africa. In the years since Dr. Goodall began, scientists have reaped a bounty of data from chimpanzee study sites, yielding new insights not only into chimpanzee culture, but into our own culture as well.
Chimpanzees culture is much like human culture: groups in different areas share different cultures. Tool-making is a good example of this variation. Chimpanzees in Gombe use long twigs and alter them for better termite fishing while chimpanzees of the Tai Forest in Cote d'Ivoire are more often seen nut-cracking with rocks and planed surfaces. Even chimpanzees living in separated areas in the same countries will exhibit different cultures and behaviors.
But what kind of behaviors do most sub-species and groups of chimpanzees share? General behaviors like group structuring, communication, and hunting practices are often common from chimpanzee group to chimpanzee group, and even these factors are never constant!
Chimpanzees communicate using a wide variety of calls, postures and gestures. The food calls -- a mixture of grunts, barks, and pant hoots -- alert other chimpanzees to the location of a food source. A special excited intensity of these calls indicates that there has been a successful kill after a hunt. Each individual has his or her own distinctive pant-hoot, so that the caller can be identified. A loud, long, savage-sounding ‘wraaaa’ call is made when a chimpanzee comes across something unusual or dangerous. When young chimpanzees play, they emit breathy laughter. Soft grunts uttered by foraging or resting chimpanzees maintains communication within the group.
Posture, gesture, and facial expression communicate many messages and emotions within a Chimpanzee community. When greeting a dominant individual after an absence or in response to an aggressive gesture, nervous subordinates may approach with submissive signals - crouching, presenting the rump, holding the hand out - accompanied by pant-grunts or squeaks. In response, the dominant individual is likely to make gestures of reassurance, such as touching, kissing, or embracing the subordinate.
Friendly physical contact is crucial in maintaining good relationships among chimpanzees. For this reason, social grooming is probably the most important social behavior, serving to sustain or improve friendships within the community and to calm nervous or tense individuals. The grin of fear seen in frightened chimpanzees may be similar to the nervous smile given by humans when tense or in stressful situations. When angry, chimpanzees may stand upright, swagger, wave their arms, throw branches or rocks - all with bristling hair and often while screaming or with lips bunched in ferocious scowls. Male chimpanzees proclaim their dominance with spectacular charging displays during which they slap their hands, stamp with their feet, drag branches as they run, or hurl rocks. In doing so, they make themselves look as big and dangerous as they possibly can, and indeed may eventually intimidate a higher-ranking individual without having to fight.
One of the first and most significant discoveries made by Jane Goodall was that chimpanzees hunt for and eat meat. During her first year she observed a male chimp (David Greybeard) an adult female, and a juvenile eating was a young bushpig. Before this, it had been assumed that chimpanzees ate only fruit and leaves!
On that first occasion it was not clear whether the chimpanzees had caught and killed the prey, or merely come upon a carcass. However a short time later Jane actually observed the hunting process when a group of chimpanzees attacked, killed, and ate a red colobus monkey. The hunters covered all available escape routes while one adolescent male crept up after the prey and captured it, whereupon the other males instantly rushed up and seized parts of the carcass.
Successful hunters typically share some portion of their kill with other group members in response to a variety of begging behaviors. Most of the captured animal is eaten, including the brain! Meat is a favored food item among chimpanzees, but makes up less than two percent of their overall diet.
Chimpanzees live in social groups called communities or unit groups. At Gombe, there have been between 40 and 60 individuals in the main study community (Kasakela) since 1960. Communities may be larger in other areas, or may be reduced to very small remnant groups. Chimpanzees' social structure can be categorized as "fusion-fission", meaning they travel around in groups of up to six individuals. The organisational structure of these groups is constantly changing as individuals wander off on their own for period of time, 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 estrus. Mothers and dependent young up to the age of seven 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 scattered groups by means of the distance call: the pant hoot.
Within the community, a male hierarchy establishes social standing, with one dominant male as the alpha. Females have their own, somewhat confused, hierarchy. All adult males dominate all females. Consequently most disputes within a community can be resolved by threats rather than actual attacks. However, the males within a community regularly patrol their boundaries, and if they encounter individuals of a neighboring 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 natal group.
When a female is in estrus and sexually attractive and receptive to the males, the skin around her rump swells considerably and is clear pink. Females show their first very small sexual swellings at age eight or nine, but are not sexually attractive to the older males until they reach age 10 or 11. There is usually a two-year period of adolescent sterility before the female finally conceives. Spacing between births, provided the previous infant lives, is about five years.
Some females in estrus are more attractive to the males than others. A popular female may be accompanied by many or even all of the adult males in her community. Alternatively the dominant male may become possessive of her and prevent the other males from attempted mating. Another interesting mating pattern is the consortship, during which a male persuades a female to accompany him to some peripheral part of the community range. If he is able to keep her there, away from other males until the time of ovulation, he has a good chance of siring her child. Even low-ranking males can become fathers if they have the skill to lead a female away at a time in her reproductive cycle when she is not interesting to the high-ranking males. At Gombe, chimpanzee males may be capable of reproduction at age 12 or 13, but are not socially mature until a few years later.
"I've spent many hours pondering how complex and sophisticated are the workings of a chimp's mind, but I still have far more questions than answers."
--Bill Wallauer, Gombe videographer
Many of us have questions about the consciousness, perspective and feelings of our closest relative, the chimpanzee. Below, JGI's videographer, Bill Wallauer -- who daily treks through the forest taking hours and hours of footage of Gombe chimps -- offers his thoughts about these questions in light of the magnificent waterfall displays chimpanzees perform, and also their reactions to other beings in nature. He eloquently shared his insights in response to a cultural anthropologist's query.
Dar es Salaam
14 Feb. 2002
Thank you for your letter. I too am fascinated with they way primates see their world. Questions of awe, reflection, appreciation, and level of understanding, are constantly on my mind as I watch the Gombe chimpanzees react (or not) to their physical environment.
I think that little has been published because it is impossible for primatologists to quantify what 'may' be going on in the minds of apes or monkeys. Most hesitate to publish anything that would be construed by others as anthropomorphic.
In my time at Gombe (about nine years since 1992) I have witnessed an average of two to three waterfall displays and rain dances per year. They have ranged from single individual solitary events to a single individual participant within a social group, to multiple participant events. The displays I have witnessed were performed by males of all age groups. Rarely have I seen adolescents or infants displaying in and around adult males, but it does occasionally happen. The displays are prolonged, lasting as long as five minutes, sometimes more. Aggression is occasionally an element of the display, but usually the event continues long after the subordinates have moved away. My feeling is that dominance plays a secondary role (if any) in most of this type of display. Rain dances are performed more often toward the beginning of the rainy season. I do not have a sense of seasonality in relation to waterfall displays.
I do not recall seeing a female perform an extended rain dance or waterfall display, but Dr. Goodall has and I am not at all surprised that they do.
I have discussed these displays at length with Dr. Goodall over the years. One of the most interesting and scrutinized events I have recorded on video was a waterfall display performed by the alpha at the time, Freud. Freud began his display with typical rhythmic and deliberate swaying and swinging on vines. For minutes he swung over and across the eight to 12-foot falls. At one point, Freud stood at the top of the falls dipping has hand into the stream and rolling rocks one at a time down the face of the waterfall. Finally, he displayed (slowly, on vines) down the falls and settled on a rock about 30 feet downstream. He relaxed, then turned to the falls and stared at it for many minutes. It was one of those times that I would give body parts to know what was going through a chimp's mind. Dr. Goodall and I have seen several events in which the participants seemed to ponder or consider the natural event to which they were reacting.
To your question of "the perceptual/cognitive problem of telling what's alive from what's not", I would answer that chimpanzees almost certainly know that waterfalls and rain are not alive in the same way baboons, pythons, pigs, and the other creatures of the forest are. However, the displays in reaction to these elements of nature suggest that chimpanzees find something meaningful which could possibly be described as reverence to aspects of their environment.
During rain dance displays, lightning and thunder often, perhaps usually, precedes and accompanies the downpour. If you have experienced a storm in which the hair stands up on the back of your neck and you can feel or smell the electricity in the air, you can almost be certain that the chimps would display if they were there. In other words, the behavior is predictable under some circumstances.
An excellent example of a respect and intense curiosity of chimpanzees to an animate object is in their reaction to snakes, particularly pythons. Pythons could pose a threat to young chimpanzees, but it is not likely that any snake would take on an adult. However, when a single individual or group of chimpanzees encounters a python (even a small one), the reaction is remarkable. One would expect the chimps to issue alarm calls to warn others and as an expression of their fear, but then to move well out of harms way as soon as possible. Predictably, the chimpanzees do issue a specific vocalization called a snake wraa, but when it is uttered, the group often draws near, to stare at the snake. Some climb above if possible for a better look. Typical facial expressions are those of fear and curiosity. Physical reassurance contact is often made (especially mutual embracing), and eye contact among individuals is frequent. After tens of minutes, members finally begin to disperse. Some individuals however, (Skosha and Apollo, for instance) show exaggerated and prolonged interest. Both call time and again even after the other individuals have moved well away. I have seen both stay and stare and call for as long as 30 minutes.
It is difficult to explain why chimpanzees react to pythons in this way. It appears to be much more than keeping a close eye on a possible threat, as many species do. It also seems a great waste of energy and time. If pythons are dangerous, it would make much more sense to alarm call and move away as quickly as possible.
The only case of possible projected 'animation' on an inanimate object is that of a young female chimpanzee carrying and cradling rocks and sticks in mimicry of nurturing behavior. I cannot be sure that this is exactly what I was seeing, but Gaia on several occasions has shown what appeared to be mothering behavior toward objects, much as human children care for dolls. There is a fine line between hugging and holding on, but I have seen Gaia groom both rocks and sticks as she held them in her lap. There is a similar observation of a young female baboon at Gombe who was observed mothering a rock.
What does this all mean? We can't come to any real conclusions, but I honestly do believe that chimps have the capacity to contemplate and consider (even revere) both the animate and inanimate. Where the line is drawn between what is alive and what is not I fear will always remain a mystery.
I've spent many hours pondering how complex and sophisticated are the workings of a chimp's mind, but I still have far more questions than answers.
--Bill Wallauer, Gombe videographer
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