Pan is a highly intelligent, socially organized, and culturally/technologically diverse ape that has habituated themselves to the equatorial African rain forests, woodlands, and grasslands. Both Pan troglodytes (common chimpanzee) and Pan paniscus (pygmy chimpanzee or bonobo) exhibit specific anatomical and socio-cultural adaptations that warrant separate species designation. The common chimpanzee is larger, demonstrates much higher levels of male – male competition, lives in larger male dominated social communities, and consumes higher quantities of meat than the bonobo. Bonobo’s have longer limbs in relation to their body size than the common chimpanzee, live in a female dominated society with relatively a low level of male aggression, and demonstrate extremely high levels of sociosexual behavior. Both species are fairly sexually dimorphic. Males are approximately 15% larger than females in Pan troglodytes and 10% larger in Pan paniscus (Fuentes).
Chimpanzees live in fission-fusion social communities of 15 – 120 animals. Their communities are characterized by male philopatry, female dispersal, and consist of revolving multi-male/multi-female subgroups. In both species, males form coalitions in an attempt to coerce females, patrol and defend the community territorial boundaries, and hunt antelope, birds, and monkeys (Burnie and Wilson). As are most apes, chimpanzees are mainly frugivorious but they also consume seeds, nuts, flowers, eggs, and when meat is desired, red colobus monkeys are the preferred choice. The average life expectancy for chimpanzees is 37 – 45 years in both captivity and the wild. After an 8 month gestation period, the infant will be reared by its mother for 3 – 4 years and sleep in its mothers nest for 5 – 7 years. At 12, females reach sexual maturity and leave their natal community for their neighboring counterparts who reach maturity at 15 years old.
Of every animal on the planet, chimpanzees are our closest living relatives. Chimpanzees share more DNA with humans, over 98%, than with their African Pongid cousin, the gorilla (Stanford, et al.). Chimpanzees demonstrate some behaviors that were, until recently, deemed “human.” These highly k-selected apes show tremendous amounts of inclusive fitness within each community. Social grooming, play, and care for the elderly and young are essential for the maintenance of the population. Chimpanzees communicate through a series of distinct vocalizations and facial expressions. This genus creates and implements tools (termite sticks, nut and shell crackers) which vary according to the ecological setting of the community and thus are culturally transmitted. The most telling of these behaviors is the frequent sociosexual activities observed in P. paniscus and the intense warfare of P. troglodytes. It is argued that 7 – 11 million years ago the last common ancestor shared by chimpanzees and humans existed. Many researchers are convinced that chimpanzees are the model study for early hominid behavior.
Each species of Pan is recognized as endangered. Their numbers in the wild are estimated to be between 150,000 – 200,000 for P. troglodytes and at 25,000 for P. paniscus (Stanford, et al.). Deforestation and hunting by humans is the main threat to their survival.
• Height: 2.5 – 3.5 feet
• Weight: 66 – 130 pounds
• Status: Endangered
P. troglodytes inhabit 21 countries throughout equatorial Africa. They form patriarchal societies featuring immense male – male competition in which both sexes compete for hierarchal dominance. Upon reaching sexual maturity, males will attempt to form or join an existing coalition of males. These coalitions have one ultimate goal…communal dominance and within that, production of the alpha male. The alpha male has prime access to all sexually receptive females and food, with the members of his coalition falling into place accordingly, a key factor in keeping his position. He relies heavily on the support from his coalition of males and from the influential females in the group. His dominance is demonstrated and maintained through intense terrorization (the alpha’s hair will almost always “stand on end” in an effort to increase size) and aggression, mutual grooming, and social bonding. Females attain dominance in much the same manner, but with less violence. Research on age influences in chimpanzee communities conducted by Kate Baker indicates that, “Older chimpanzees show much less aggressive behavior than adult chimpanzees. As males age their dominance has a tendency to increase, whereas with females it is the opposite. Younger chimpanzees made themselves much accessible to play objects and have higher instances of locomotive behaviors.”
Examinations of the ecological impact on hunting strategies help to provide evidence of a cultural transmission of knowledge. According to Strier, “Comparative studies of red colobus monkey hunting strategies in two communities of chimpanzees (Bshary and Noe, 1977) from Gombe National Park and Tai National Park reveal stark contrasts. At Gombe the forest has a low uneven canopy making it difficult for the monkeys to hide. The Tai forest canopy is high and even. Also unlike Tai, the Gombe red colobus are aided by the neighboring Diana monkeys and their warning calls. At Gombe, the chimpanzees are smaller and the red colobus monkeys are larger and more aggressive (with numbers will fight off chimpanzees) than their Tai counterparts. Tai chimpanzees are forced, by the canopy of the forest, to work together in an effort to drive the hiding monkeys. Gombe chimpanzees hunt in an individualistic and opportunistic fashion, relying on the forest canopy and the element of surprise. Both hunting (teamwork vs. surprise) and defensive (flight vs. fight) strategies are shaped by their respective ecologies.”
The chimpanzee male is an extremely territorial and testosterone driven animal. Food and females are their most prized possessions and they are willing to kill for them. According to Mitani, et al., “Patrols are conducted in a tight file and are very silent and tense. Males search for any sign related to feeding, dung, and nests. If any outsider(s) are encountered and the patrolling party is superior in numbers violence will ensue. Warfare has been observed as an attempt to gain access to additional females and food.” This involves the complete annihilation of a neighboring community, the kidnapping and assimilation of “spared” females for use as sexual resources, and the cannibalized rationing of juveniles and infants. The sharing of meat after the hunt or as the spoils of war helps to reinforce the dominance of the alpha male, his coalition, and group solidarity.
• Height: 2.5 – 3.5 feet
• Weight: Approximately 86 pounds
• Status: Endangered
P. paniscus is found in only one country: the Democratic Republic of Congo. They inhabit the nucleus of the Congo Basin, the second largest rain forest on earth. Bonobo society is characterized by female dominance and sociosexual behaviors. Females of this species freely use non-reproductive sexual intercourse in an effort to eliminate conflict/reduce tension and reinforce alliances. The vast majority of male – male and male – female disputes are settled with sexual encounters. Almost all female – female disputes are settled with intense g-g rubbing (Fuentes).