Pygmy Chimpanzee (Bonobo)
The bonobo is lacking in a tail as are all extant apes. The pelage color is black and may turn more of a grayish color with age. The forearms are longer than the hindlimbs, and the bonobo has a short thumb. The average body mass for an adult male bonobo is around 39 kilograms, and for the female it is around 30 kilograms. There is sexual dimorphism in the canines where the males' are longer than the canines of the female. The skull of the bonobo is more gracile than Pan troglodytes and the limbs are more slender (Fleagle, 1988).
the bonobo is found in the country of Zaire. This species prefers to live in dry, primary forests in the crowns and the shrub levels of the forest.
The bonobo is primarily a frugivorous species, but it will also consume shoots, leaves, flowers, seeds, bark, pith, herbs, invertebrates, and small vertebrates. This species will use over 113 types of plants in a year. Of the vertebrates eaten are flying squirrels and the young of forest duikers. The bonobo will also consume termite clay for essential minerals (Nishida and Hiraiwa-Hasegawa, 1987). When fruit becomes scarce during the dry season the bonobo will consume more shoots, pith, herbs, and the stems of ground plants (Nishida and Hiraiwa-Hasegawa, 1987). This is a diurnal and a semi-terrestrial species, although it is more arboreal than . Groups of bonobos range from about 50 to 100 individuals, although they do break up during the day to form foraging parties. Each night this species makes a sleeping nest made from branches and leaves (Estes, 1991).
When the bonobo moves on the ground it moves in a special position called knuckle-walking (Fleagle, 1988). In the tree this species also moves in a quadrupedal manner (Fleagle, 1988). The bonobo also uses suspensory behavior in the trees to move around within a feeding source (Fleagle, 1988). On the ground the bonobo can also walk bipedally (Estes, 1991).
The bonobo has a fission-fusion society, and the subgroups are generally multimale, bisexual groups with matrifocal subunits (Nishida and Hiraiwa-Hasegawa, 1987). This species has a promiscuous mating system. These communities have ranges that overlap with other groups (Estes, 1991). Males of this species will protect members of the group as well as hunt (Estes, 1991). Males are philopatric while females are the ones who will disperse (Estes, 1991). Most of the grooming bouts and instances of food sharing occur between males and females, which is different from Pan troglodytes where it occurs between males (Nishida and Hiraiwa-Hasegawa, 1987). Also the female-female relationship is much stronger in this species than it is for Pan troglodytes (Nishida and Hiraiwa-Hasegawa, 1987).
submissive greeting: This call sounds like "ku-ku-ku-ku" and is given by subordinates when they approach more dominant individiuals (Nishida and Hiraiwa- Hasegawa, 1987).
open mouth grin: This is where the mouth is open, the corners of the mouth are drawn back, and the teeth are showing (Estes, 1991). This display is shown when an individual is threatened by a more dominant individual that it fears (Estes, 1991).
open mouth threat: This is where the mouth is open, the teeth are covered by the lips, and the eyes are staring forward at the receiver (Estes, 1991). This display is done to threaten a subordinate (Estes, 1991).
tense-mouth face: This is where the lips are compressed tightly and the eyes are staring at the receiver (Estes, 1991). This display occurs before or during the chasing of a subordinate and before or during copulation (Estes, 1991).
pout face: This is where the eyes are opened and the lips are pushed forward making an "O" shape (Estes, 1991). This display occur in circumstances of frustration or anxiety such as after an attack, rejection of grooming, when an infant is lost, and after detecting a strange object (Estes, 1991).
play face: This is where the eyes are open and the mouth is open but the teeth are not showing (Estes, 1991). This display occurs during play with other conspecifics (Estes, 1991).
social presenting: This is where the individual is in a quadrupedal stance with the rump facing the receiver (Estes, 1991). This is performed by females to males and by subordinate males to more dominant males (Estes, 1991). Open mouth grin may occur by the individual as they look over their shoulder at the receiver (Estes, 1991). This is a submissive stance and occurs after an attack by the attackee (Estes, 1991).
wrist-bending: This is where an individual presents the back of the hand to another's lips (Estes, 1991). This is done by adults and juveniles to infants, a reassuring gesture (Estes, 1991).
reaching and touching: This is where an individual will touch with the hand the head, back, or rump of another (Estes, 1991). This acts as a submissive or appeasement gesture or a reassurance gesture as a response to social presenting (Estes, 1991).
patting: This functions as a reassurance gesture to a distressed subordinate and is done by a more dominant individual (Estes, 1991); the individual softly touches the receiver on a part of the body.
embracing: This is where an individual wraps one or two arms around another from the front, back, or side (Estes, 1991). This is often done by a mother to her frightened infant (Estes, 1991).
submissive mounting: This is where a subordinate will mount a superior after being charged or attacked, and he grasps the individual around the waist, pelvic thrusts, and sometimes grabs the scrotum with the foot (Estes, 1991).
reassurance mounting: This is where a dominant individual mounts a subordinate and is a response to social presenting (Estes, 1991).
social grooming: This is where one individual will remove parasites and/or dead skin from another. This functions in maintaining social bonds and is usually done between females (Estes, 1991). In the bonobo this also occurs between family members (Estes, 1991).
The bonobo gives birth to a single offspring. During estrus the perineum of the female will swell up (Estes, 1991). The bonobo is the only primate besides man who engages in mating for other purposes than procreation. Mating is not only dorso-ventral, as it is in Pan troglodytes, but it is also ventro- ventral, or face-to-face (Nishida and Hiraiwa-Hasegawa, 1987). Amongst females genital-genital rubbing, or G-G rubbing, is common and serve to communicate reassurance (Nishida and Hiraiwa-Hasegawa, 1987). Females will lay on top of each other face-to-face and move their pelvises so that the clitoris of each rubs together. Also juvenile males will rub each others genitals and place their mouths on each others genitals. Young bonobos often join in with the adults when they are having intercourse. Both males and females solicit copulations (Nishida and Hiraiwa-Hasegawa, 1987). Generally most matings occur in the morning, with the second time period for occurance happening in the evening (Nishida and Hiraiwa-Hasegawa, 1987).
Burton, F. 1995. The Multimedia Guide to the Non-human Primates. Prentice- Hall Canada Inc.
Estes, R. D. 1991. The Behavior Guide to African Mammals. University of California Press.
Fleagle, J. G. 1988. Primate Adaptation and Evolution. Academic Press.
Nishida, T. and Hiraiwa-Hasegawa, M. 1987. Chimpanzees and Bonobos: Cooperative Relationships among Males. In Primate Societies. eds. B.B. Smuts, D.L. Cheney, R.M. Seyfart, R.W. Wrangham, and T.T. Struhsaker. University of Chicago Press.
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