Bonobo or Pygmy Chimpanzee

Species: Pan paniscus.

PHYSICAL DESCRIPTION: Male Ht. 3.5-4.2 ft., Wt. 75-100 lbs. Female Ht. 3.0-3.8 ft., Wt. 60-90 lbs. Coat: Black, turning gray with age. Tufts of hair over ears. Skin black on hands and feet, variable brown to black on face. Large brains (300-400 cc). Quadrupedal knuckle-walking. Longevity: about 40 years in wild.

GEOGRAPHIC LOCATION: Central Africa, between Zaire and Kasai rivers.

ECOLOGY: Semi-terrestrial folivores and frugivores. Humid forest. Home range: 10 - 20 km2 Day range: 1 - 3 km. Population density: variable, approx. 5.0 / km2

DIET: Terrestrial vegetation, fruit, flowers, soft pith, young leaves.

SOCIAL ORGANIZATION: Multiple-male polygynous groups (20-120 individuals, avg. 40), no solitary individuals. Both male and female transfer (?). Variable female dominance hierarchy, highly significant female ties. Grooming most frequent among females, with male-female grooming moderately frequent (note difference with common chimps). Male dominance hierarchy variable, less significant than among common chimps (see reference below). Territorial defense less obvious than in common chimp. Females forage in groups. Aggression among females is uncommon, but male-male conflicts are more frequent, usually involving multiple individuals. "Reconciliation" (e.g., touching, grooming) is common after within-group conflicts. Highly intelligent, self-aware, apparent purposeful deception of others, sophisticated social manipulation tactics. Complex communication system, with many non-verbal signals.

REPRODUCTION: Little birth seasonality. Males sexually mature at 16 yrs., females at 12 yrs. Gestation length: 8.0 months. Obvious estrus swellings for about 20/35 days. Frequent sex, copulation duration aprox. 15 sec., approx. 40% ventro-ventro. Pre-copulatory signals such as eye-gazing are common (unlike common chimp). Litter size: 1. Interbirth interval: 4 yrs. Infant birth wt.: 5 lbs. 40% infant mortality in first 3 yrs.

PARENTAL CARE: Infants carried by females for 1-2 yrs. Walk at about 9 months. Weaning at 3 ys., but offspring stay with mothers until thay are at least 6 years old. Long term relationships between mothers and offspring exist, even into adulthood.

TOPICS OF SPECIAL INTEREST: Linguistic and cognitive abilities, female "G - G rubbing," comparisons with common chimps and humans.

BIBLIOGRAPHIC SOURCES:

Nishida, Toshisada, & Hiraiwa-Hasegawa 1986. Chimpanzees and Bonobos. In: Primate Societies, ed. Barb Smuts et al. Chicago: University of Chicago Press.

de Waal, Frans 1990. Peacemaking among primates. Cambridge: Harvard.

Wrangham, R.W. et al. 1996. Chimpanzee Cultures. Cambridge: Harvard.

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