Bonobo, Pan paniscus 2009 (minor update April 2013)

Fact Summary Taxonomy and Nomenclature Distribution and Habitat Physical Characteristics Behavior and Ecology Diet and Feeding Reproduction and Ecology Managed Care Pathology and Diseases Population and Conservation Status Bibliography

Photo courtesy of the Primate Gallery

Describer (Date): Ernst Schwarz (1929) (Pan satyrus paniscus). Revue Zool. Africaine, 16:425, April 1 1929.
Given species name (Pan paniscus) by Harold Coolidge (1933). Am. J. Phys. Anthropol. 18:1-57, Sept. 1933.

Kingdom: Animalia
    Class: Mammalia
        Order: Primates
             Superfamily: Hominoidea
                    Family: Hominidae
                          Subfamily: Ponginae (Includes: orangutans)
                               Genus: Pongo
                          Subfamily: Homininae  (Includes: gorillas, bonobos and chimpanzees, and humans)                       
                                Genus: Gorilla
                                Genus: Pan 
                                     Species: Pan paniscus - bonobos
                                     Species: Pan troglodytes - chimpanzees
                                         Subspecies:
                                 Genus: Homo   (Includes modern humans and several extinct species)
                    Family: Hylobatidae (Includes gibbons and siamangs)

• Above taxonomy is according to Groves (1989) who recommended that the four great ape genera be combined into one family, Hominidae, with orangutans in a separate subfamily from the other three. Wilson & Reeder (2005) would eliminate the separate subfamilies and group all four together as hominids. Other taxonomists would place the orangutans in their own separate family, Pongoidae.
• Bonobos (Pan paniscus) and chimpanzees (Pan troglodytes) are distinct species, according to both morphological and genetic data collected in many recent studies (Won & Hey 2005).
  • Bonobos initially described incorrectly as subspecies of the chimpanzee, Pan satyrus (Schwarz 1929); reclassified as separate species, Pan paniscus, four years later (Coolidge 1933)
• Bonobos and chimpanzees are sister species, and each is equally closely related to humans. Together they are humans' closest relatives. (Maclaurin & Sterelny 2008, Kaessmann et al 1999)
  • Recent DNA sequencing data show that the human genome is 98.7% identical with the bonobo genome (Prüfer et al. 2012) and 98.8% identical with the chimpanzee genome (CSAC 2005).
  • The genetic similarity between bonobos, chimpanzees, and humans is so high that at least one taxonomist has suggested placing them all in the same genus (Homo) (Wildman et al 2003).

• Common Names:
  • Bonobo (may be a mispronunciation of Bolobo, a town near the Zaire River region of early specimen collection)
  • Pygmy chimpanzee (based on Coolidge's 1933 species description citing Pan paniscus as being somewhat smaller than P. troglodytes and retaining juvenile traits in adulthood; bonobos, however are not smaller than all chimpanzees), dwarf chimpanzee, gracile chimpanzee
• Local Names: "Eja", "Engombe" (Limongo names); "Mokumbusu" (Lingala name)

• Several genetic studies each examining different aspects of DNA concluded that primate-like mammals diverged from other mammals some 90 million years ago, during the Cretaceous Period.
  • Fossils, however, suggest a somewhat younger date for emergence of primate-like mammals at about 65-57 million years ago (Paleocene) in Europe and North America.
• Two main primate suborders appeared before 50 million years ago:
  • Strepshirhines (lemur-like)
  • Haplorhines (tarsier-like)
  • Both the lemur-like and the tarsier-like primates were represented by several species in the Eocene fossil record of southern California.
• 40 million years ago New World monkeys diverged from Old World Monkeys.
• By 28-25 million years ago (Oligocene), earliest anthropoids divided into a lineage from which Old World monkeys and hominids (apes and humans) evolved.
• The last common ancestor of today's apes and humans lived about 18 million years ago.
• Divergence between Homo (humans) and Pan (chimps and bonobos) occurred 5-8 million years ago. (Boesch 2002) (Wildman et al 2003)
• Bonobos and chimpanzees diverged relatively recently, about 690,000-900,000 years ago according to Kaessmann et al (1999) or Won & Hey (2005) or somewhat earlier at 1.8 million years ago based on estimates by Yu et al (2003) or even earlier according to mitochondrial DNA (Gagneux et al 1999)
  • One explanation for the cause of chimpanzee/bonobo genetic separation may have been the formation of the Congo River around 1.5 million years ago which divided the population and today still prevents natural contact between the two species.

• Hybrids between common chimps and bonobos in captivity have occurred.

Found only in the central portion of Democratic Republic of the Congo (Congo Basin), south of the Congo river. The common chimpanzee has much larger range. Small populations within the Congo Basin are separated by rivers. Potential range is estimated at approximately 500,000 km sq. (193,051 mi sq) Range is discontinuous. Species absent or rare in many areas. Southern part of Congo Basin not well surveyed. Found in lowland rain forest - both primary and secondary "regrowth" forests, but also in mosaic forest with savannas where they may even feed on grasses; recent studies show them entering swamp forests where they wade in waist-deep streams. Share many ecological traits with common chimpanzees. Both are terrestrial and arboreal. Can utilize many plant resources. Few field studies prior to 1970s. Studies in 1980s confirmed populations near towns of Befale, Djolu, Bokungu and Ikela and a 3,000 sq. km. area between the Yekokora and Lomako Rivers. Based on evidence of nest building individuals, population densities of around 0.4/sq km (0.15/ sq mi) are estimated for Salonga National Park which may be similar to overall densities for all their range; some study area have higher estimates. As late as 17th century this species may have ranged into northwestern Angola and as far south as the Quanza River.

Bonobo (Pan paniscus) Distribution (Butynski 2001). Click map to see larger image. Click here for IUCN map.

• Weight: Male 39 kg (86 lbs) / Female 31 kg (68 lb)
• Whole Body Length: 700 - 830 mm (2.3 - 2.7 ft)
  
  
• Black face, ears, palms and soles of feet; individuals in captivity may have lighter pigmentation.
• Black body hair is long and fine.
  • Many adults retain the white rump tuft common to infants.
  • Hair on top of head appears to be parted down the middle.
  • Side-whiskers are long and thick.
  • Baldness does occur, although "perhaps later in life" than in other chimpanzees. (Groves 1989)
• Compared to common chimp:
  • Brow ridges and facial bone structure are less pronounced.
  • Head is more rounded, with smaller ridges above eyes, less developed muzzle, less jaw protrusion..
  • More slender build, narrower chest, bone and muscle of lower limbs is heavier.
  • Ears smaller and almost completely covered by cheek whiskers.
    • Chimps' ears stand out more from the head
  • Molars smaller.
  • Less sexual dimorphism. (Cramer and Zihlmann 1978).
  • Lips are lighter, often reddish colored. (de Waal 2001)
  • Nostrils are "thick-walled" and more gorilla-like. (de Waal 2001).
• In overall size, bonobos are not smaller than chimpanzees (most anatomical measurements overlap) but there are differences in proportion:
  • Bonobos have shorter upper limbs and longer lower limbs (Zihlmann 1996).
  • Compared to chimpanzees, bonobos have body characteristics that are better for bipedal or upright posture: (Myers Thompson 2002)
    • More centrally positioned opening in skull for spinal cord (foramen magnum)
    • Longer feet
    • Longer thigh bones
    • More body weight (heavier muscles) in lower legs of bonobos. (Zihlmann 1984)
  • Bonobos are quite similar in overall body size, cranial capacity, and lower limb length to an ancestral hominid, nicknamed Lucy, who lived some 3 million years ago in Africa. (Zihlmann 1984)
• Of all the great apes, bonobos are the most human-like in their leg length. (de Waal 2001)
• Bonobos share with humans a similar pattern of distribution of brain neuron cells called VENS (also called spindle cells or Von Economo Neurons). (Hakeem et al 2009)
  • VENs help regulate complex social interactions requiring knowledge of other individuals' mental state.
  • Neither gorillas or chimpanzees have a VEN brain cell organized in clusters like those of humans and bonobos.
  • The only other animals with some form of VEN cells are whales, dolphins, and elephants, all animals with large brains and highly evolved social awareness, including empathy.
• Pygmy chimpanzees show few individual differences in their blood groups (unlike P. troglodytes and humans).
  • Common chimps are either group A or O, and the A antigen of their red cells differs from those in human red cells.
  • Blood group studies show many differences between bonobos and common chimpanzees, enough that some researchers have suggested they should be in a separate genus. (Socha 1984)
• Humans and chimpanzees share at least 98.5% of their DNA.
  • Great apes have 24 pairs of chromosomes
  • Humans have 23 pairs (18 of the 23 pairs are virtually identical)

• Researchers at Wamba (Kano 1992; Kano et al 1996) observed a basic rhythm in daily activities:
  • Rise in early morning (0500-0600 hr). Feeding is an immediate priority.
  • After a rest period the troop leisurely travels on the ground to the next food trees, feeding on terrestrial plants as they go.
  • Gradual decline in activity around mid-day.
  • Afternoon is spent in more feeding and travel.
  • Arboreal night nests are made at or near the last feeding site.
  • Settle for the night at 1830-1930 PM.

• Largely diurnal.
• In one day:
  • 43% of day spent resting
  • 18% arboreal feeding
  • 20% terrestrial activities (travel and feeding)
  • 13% traveling
• Travel 1.5-15 km/day to forage.
• Nest construction is similar to that of common chimp.
  • Usually built in fruit-bearing trees;
  • Saplings less than 8 in diameter are favored.
  • Average nest height is 7-15 m (23 - 49 ft).
• Adult bonobos sometimes share a nest (night or day);
  • A unique behavior among African apes.

• Both bonobo and chimpanzee societies have fission-fusion social organization (de Waal 1995)
  • Both species travel through their habitats in groups of a few individuals; group composition changes constantly
  • Three kinds of social groups are formed:
    • Between mothers and their offspring; these are the most stable. (Kuroda 1989)
    • Between females
    • Between males and females
• More data is available for social behavior of wild chimpanzees than for wild bonobos.
  • Comparisons between the two species often based on insufficient data or should be interpreted with care.
  • Many studies were based on common chimpanzee populations in Tanzania that might not be typical of all chimpanzees.
• Much data on bonobo social interactions are based on Yerkes National Primate Research Center and San Diego Zoo, two captive colonies.
  • Both colonies characterized as peaceful, egalitarian, and female dominated.
  • Stevens et al (2008) caution that all captive bonobos may not share the same behaviors as these two colonies.
• Bonobo (Pan paniscus) and chimpanzee (Pan troglodytes) groups in many studies are shown to have distinct differences in social organization. (Hohmann & Fruth 2002)
  • Chimpanzee society characteristics: (Goodall 1986, Watts 1998):
    • Male dominated based on alliances with other males, often supported by considerable aggression .
    • Traveling parties tend to be small and male dominated.
    • Females tend to not travel with males in order to avoid aggression.
  • Bonobo society characteristics: (Kano 1992, 1996) (de Waal 1995, 1997):
    • Form larger parties biased towards females
    • Males show dominance relations among themselves with less aggression than shown by chimpanzees
    • Aggression by males towards females less than seen in chimpanzees.
  • Bonobo female bonds observed in captivity may be a side effect of life in captivity. (Stevens et al 2008)
• Other studies suggest "differences between chimpanzee and bonobos could be related more to the ecological conditions" than to true species differences; the two species may, in fact, have similar behavioral diversity. (Hohmann & Fruth 2002) (Boesch & Boesch-Achermann 2000)
  • Chimpanzees in dense forest habitats of Tai Forest in Côte d' Ivoire, Africa show similar party sizes and association patterns to bonobos who also occupy forest habitats.
• Both chimpanzee and bonobo societies have social interactions that are extremely variable, with the factors affecting the differences still not clear. (White & Chapman 1994)

• A study by Stevens et al (2008) found bonding patterns in four captive bonobo groups and wild populations to be similar:
  • Males established hierarchical dominance relationships among themselves
    • Males are rarely near one another and do not often groom each other.
    • Males compete for rank, which is influenced greatly by rank of mother.
    • Highest ranking males did not necessarily have the most copulations
      • Male rank did not determine mating success, probably because female mate choice also plays a role.
      • Because females' time of ovulation is hidden and multiple matings are the rule, there may be little reproductive benefit to males of being high-ranking.
  • Females establish dominance relationships among themselves, but they are less expressed or obvious than the males'.
    • Females do not groom each other more than males groom each other but they are more often near each other
    • Females support each other more often than they support males
      • Compared to chimpanzees, bonobo females in captivity are more socially integrated and bond more frequently. (Parish 1993, 1996)
    • Females exchange various types of social behaviors such as genito-genital rubbing, peering, and food sharing
      • Exchanges reduce tension and promote the formation of social bonds.
    • Females usually gather in the center of a mixed party.
      • Oldest and highest-ranking adult females with grown sons are core of group.
      • Other males tend to be lower-ranking and stay at periphery.
  • Most females can dominate males even though they are physically smaller.
    • Females are either co-dominant or moderately dominant over males.
    • Males are rarely submissive to young females, but always behave submissively to a group the female aggregate.
      • Captive female bonobos at Planckendael animal park in Belgium (in a naturalistic setting) banded together to chase away harassing males; allied females could "outcompete" individual males who were larger or stronger.
      • A similar pattern of female dominated society observed by Furuichi at Wamba in the Congo Basin where males surrendered feeding positions when females appeared.
      • In captive bonobo populations as well as the wild, females may form alliances in order to attack males. (Stevens et al 2008)
        • Attacks can be quite fierce, resulting in injuries but not death
        • Male chimpanzee attacks, by contrast, on neighbors in wild populations may result in death.
      • Even an alpha male would not strike back if attacked by an adult female. (Kuroda 1989)
  • Unrelated males and females form bonds as strong as some female-female bonds.
• Females leave their birth unit-groups as older juveniles or young adolescents and settle in another unit-group after visiting several. (Kano 1992)
  • Newly immigrated young females elicit social interactions with older females to improve their social positions.
  • After giving birth, female social status in her new group becomes more stable.
• Males stay with their mother's group and may continue to be with her even when old.
• Grooming between adult males and females is more common than observed in chimpanzees
  • Number of males vs females and overall number of individuals of the groups in which the bonobos live may determine, in part, their grooming partners.
• Bonobo society emphasizes female bonds but have a potential for male bonding (de Waal 2001)
  • Chimpanzees by contrast, emphasize male bonding with a potential for female bonding.
• Bonobos show no formal signs of submission like the pant-grunting and bobbing of chimpanzees. (Stevens et al 2008)
• Behaviors which may be called "reconciliation" seems to function to preserve long-term relationships. (de Waal 2001)
  • Sitting next to one another in contact and grooming help to reconcile or console individuals after conflict.
  • Both male and female bonobos, in contrast to chimpanzees, often use sexual behavior either to ease tension in aggressive situations or in the aftermath of aggression.
  • The fact that there is a need for reconciliation suggests that it would be wrong to think of bonobos as entirely peaceful; the level of violence is merely lower in general than seen in chimpanzees.

• Interactions between communities haven't been often observed but appear to consist of "vocal contests" and avoidance of confrontation.
• Wamba has highest density of bonobos (1.7 per sq km). Average common chimp density is 2.6-6 per sq km.
• Bonobos do not typically react with aggression when meeting individuals from neighboring territories. (de Waal 1995, 2001)
  • Lethal aggression (infanticide, cannibalism, warfare) hasn't been observed to date. (de Waal 2001)
  • This is a significant contrast with common chimpanzees who often engage in aggression when meeting neighboring individuals.
• At Lomako, female bonobos range territories equal or greater in size to the range of the males. (White & Waller 2008)
  • By contrast chimpanzee females range over an average of only 70% of male ranges.
  • Bonobo males do not form raiding parties that seek to reduce or eliminate neighboring males, gain additional mates, and expand their territories as do male chimpanzees
  • Current behavior studies seek to understand why bonobos don't conduct lethal raids; there may be more advantage to bonobo males in simply predicting females' travels across their large ranges.

• Hand (and even foot) gestures play "a significant role in bonobo communication"
• Some gestures are tactile in nature (involve gentle touching and patting)
  • More common among bonobos than chimpanzees.
• Hand gestures used by apes are even more flexible than monkeys' facial expressions and vocalizations.
• Gestural communication along with vocalizations, may be the route by which "symbolic meaning was acquired in our hominid ancestors".
  • A hand gesture by an ape depends on its context (what's happening at the time)
    • A begging gesture, for example, can mean either a desire for support during a fight or a desire to share food from another individual (Corballis 2002, Pollick and de Waal 2004).
• Use of gestures combined with facial/vocal signals makes getting a response more likely than when only gestures are used.

• Elaborate sociosexual behaviors are an important aspect of social relationships for juveniles and adults of both sexes
  • Sexual behavior is flexible and quite variable; occurs between sexes and in same-sex pairings.
    • Male-male mounting and rump contact is common
      • Presumably used to defuse tense situations.
    • Similar behavior among females consists of genital rubbing.
      • Genito-genital rubbing is commonly seen in interactions over food but may happen at other times too.
      • May strengthen group integrity and maintain bonds.
  • de Waal has developed detailed social ethogram (1988).
  • Sexual behavior has important social functions as well as reproductive functions, as it does in human society. (Kano 1989)
• Peering behavior (prolonged close proximity gazing by one bonobo towards another) common
  • May function to prompt positive interactions between the two individuals
  • Not common between adult males. (Idani 1995).
• A long period of sexual attractiveness may play a role in female-female as well as male-female sociosexual contacts. (Paoli et al 2006).

• Bonobos are better able to "regulate their vocal output" when compared with chimpanzees.
  • Such regulation may make getting a desired response more likely.
  • Bonobos produce "vocal chatter" to get attention in the absence of excitement.
  • Low-intensity vocalizations by bonobos signal the presence of food.
  • Chimpanzees produce vocalizations mainly in highly charged situations such as aggression or when expecting food.
• 14 reported vocalizations (de Waal 1989).
• Upon arriving at a preferred food source, large parties of bonobos will emit simultaneous food calls.
  • Calls inform members of party of food source
  • May inform other groups of party size
• Have a distinct high-pitched "metallic" alarm call which both males and females emit.
• May hiss in tense situations.
• Chimp-like pant-grunt sounds rare; instead, faint "ku,ku,ku"

• Most long-distance travel is done on the ground, using "knuckle-walk" (a quadrupedal motion with the fore-limbs utilizing the dorsal surface of the knuckles for support/weight-bearing).
• When carrying food or other objects, tripedal (one hand down on ground) and bipedal gaits are used.
• Although the bonobos can walk bipedally, this behavior is not as specialized as it is in humans.
  • When walking upright the back is held straighter, more human-like, than that of chimpanzees. (de Waal 20021)
• Far more arboreal than the common chimp:
  • Engage in arm swinging (alternating hand-to-hand progression beneath branches),
  • "Quadrupedal scrambling" on top of branches and boughs
  • Leaping and diving as a means of transferring from tree to tree
  • Vertical climbing: more versatile than gorilla climbing
  • Have been known to travel over 1 km through the trees from 1 food source to another.
  • When alarmed arboreal travel may be used to escape.
  • Vertical jumping used in trees and on the ground.
• May wade in shallow streams and pools while feeding and traveling
  • Gather algae and aquatic vegetation in waist-deep water
  • Chimpanzees avoid going into the water; may invent a tool for safely sweeping for algae from the shore (Matsuzawa 2000)

Tool use (Ingmason 1996) (Hohmann & Fruth 2003)

• Only rarely seen in the wild
• Behaviors observed in wild include:
  • Constructing a rain hat out of branches
  • Shaping a twig for a toothpick
  • Using mosses to sponge water to drink

Play (de Waal 1989) (Enomoto 1990) (Kano 1992) (Palagi & Paoli 2008)

• Bonobos are extremely playful.
  • Some 17 categories of play behavior noted by Palagi & Paoli (2008) in a study of bonobos at Apenheul Primate Park in the Netherlands.
    • Airplane, Grab Gentle, Play Push, Play Bite, Play Recovering a Thing, Play Slap, Tickle, Pirouetting, Acrobatic Play, Play Run, Play Stamping, Rough and Tumble, Play Brusque Rush, Play Retrieve, Play Invitation, Play Face, Full Play Face)
    • Play sessions typically begin with a signal that: "this is play"; playful facial displays often began a bonobo play encounter.
• Play was predominantly rough-and-tumble between juveniles observed at Wamba in the Congo Basin.
• Play between adults and between adults and juveniles was also observed at Wamba.
  • Play may have a role in courtship and is often a part of sexual encounters.
  • Adult bonobos seem to have no age preferences when it comes to choosing a play partner; chimpanzee adults, however, usually play with juveniles.
• Adult females exhibit much social play, which is unusual for primates, and more like that of the spotted hyaena. (Palagi & Paoli 2008)
  • Adult females play mainly with each other.
  • Both the spotted hyaenas and bonobos have female dominance and a fission-fusion social structure.
• Adult play may have a role in reducing tensions between individuals or in social assessment. (Palagi & Paoli 2008)
  • Captive bonobos played more during times before feeding, perhaps because they anticipate tension.
• Bonobos in captivity observed a level of social reciprocal play (such as object catching) comparable to human children.
  • If a game is deliberately stopped the bonobos attempted to cajole the partner into resuming the game.
  • Common chimpanzees don't try to re-start the game and soon lose interest.

• Omnivorous: eat plants and animals.
• When plentiful, fruit (pulp and seed) constitutes over 50% of diet.
• Important fruit sources at Lomoko: Dialium, Upaca guineensis, Ficus, Antiaris toxicaria, Pancovia laurentii, Polyalthia suaveolens, Anonidium manii.
  • Other important plant foods: pith, leaves, leaf petioles, seeds and flowers.(Crudia laurentii, Strombosiopsis tetrandra, Dioga zenkeri, Scorodophloeus zenkeri).
  • Honey, eggs, soil, mushrooms and insect larvae are also eaten.
  • Animal foods only a small part of diet: beetles, bees, butterflies, snakes, shrews, earthworms, millipedes, occasionally small mammals (young duiker).
• Favorite, preferred fruits at Wamba: Anonidium, Canarium, Dacryodes, Cissus, Treculia.
• Several researchers note a correlation between a habitat with abundant fruits and the party size of the bonobos.
  
• Discovery of preferred fruits prompts bonobos to "fall into a state of excitement" where they eat voraciously, chase, beg, greet, appease, make feeding grunts, whoop loudly and copulate often. (Kano & Mulavwa 1984)
• Meat-eating by bonobos in wild:
  • Observed eating infant duikers (Badrian N, Malenky R. 1984. In: Susman RL, editor. The pygmy chimpanzees: evolutionary biology and behavior. New York: Plenum Press).
  • Observed eating flying squirrels (Ihobe H. 1992).
• Bonobos find most of their food in the trees at a height of 25 to 40 m (82 to 131 ft) (Kano 1992)
• Bonobo foraging strategies as seen at Lukuru were more variable than previously reported due to fact that they occupy these drier and more open habitats in addition to wet forests habitats studied previously. (Myers Thompson 2002)
  • Field studies now look for parallels (and differences) between chimpanzee foraging strategies and those of bonobos when the two species ecological settings are similar.
  • Average size of foraging parties for bonobos at Lukuru: 6.4 individuals; at Lomako, about 5 individuals.
  • At Lukuru large groups of 18-25 bonobos gather regularly at permanent pools for feeding on aquatic vegetation
• Total feeding time (arboreal and terrestrial does not exceed 30% (Wamba). Common chimp spends 46-60% (Gombe)
• Not often seen drinking from standing water - may satisfy fluid needs primarily with fruit juices.
• Food sharing common. Frequently associated with genito-genital contact in various age-sex class combinations.
• Bonobos at Wamba did not like bananas or papayas, which were offered to them in food trials.

• Female bonobos, like chimpanzees, have pink genital swellings that appear attractive to males.
  • In chimpanzees and bonobos these swellings coincide with times of heightened fertility.
  • In bonobos, times of maximum genital swellings last about 13.4 days (Paoli et al 2006)
    • In chimpanzees, the maximum swelling period is 2 or 3 days less. (Furuichi & Hashimoto 2002)
  • Bonobos are sexually receptive for a large portion of their reproductive cycle, even when not near the time for ovulation.
    • This trait has sometimes been called concealed ovulation because the male has no clear signal for the optimum time for mating.
  • Bonobos also engage in sex in non-swelling phases of their cycle in about 1 out of 3 copulations.
  • Chimpanzee females tend to be sexually active only during their maximum swelling phase.
  • Visible swelling cycles do not correlate exactly with the menstrual and ovulation cycles, but these visible signs are the ones often documented in field studies as indicators of sexual phase. (Vervaecke et al 1999) (Reichert et al 2002)
    • Time between menstrual cycles averaged around 33.8 days for six studied captive bonobos.
    • Menstrual cycles in most published studies show considerable variation for bonobos.
  • Bonobo females may be found with in mixed-sex parties, regardless of the condition of their genital swelling. (Furuichi & Hashimoto 2002, 2003)
    • Chimpanzee females may seek to limit their time in groups with males due to the increased difficulty in obtaining food since males are strongly dominant;
    • Bonobos may typically have more abundant food resources in their wild habitats and they are also not subordinate to males, so there is little cost to them in being in groups that include males.

• Mutual gazing occurs prior to and during copulation.
• Copulation may occur either face-to-face or with the male behind the female, as in dogs.
  • Face-to face copulation occurs in about 1/3 of matings; this behavior is almost unknown in chimpanzees.
  • Females may copulate several hundred times for one conception as do chimpanzees. (Hashimoto & Furuichi 2006).
• Females produce first offspring at about 13 or 14 years. (de Waal 1997)

• 231-244 days (about 8 months);
• One animal studied at San Diego Zoo had a gestation period of 255 days. (Kuroda 1989)

• 4-6 years (Kano 1992, de Waal 1997)

• Weight of four newborns studied at San Diego Zoo: 1.27 kg (2.8 lb)
• Bonobo infants grow more slowly than chimpanzee infants, both physically and behaviorally. (Kuroda 1989)
  • For the first three months not seen leaving mother.
  • At 6 months venture up to 1 m (3 feet) away.
  • At 10 months may wander up to 4 m (13 ft).
  • By one year can navigate on all fours.
• Delayed development may "foster food sharing, behavioral flexibility, complicated communication, matrilineal groupings, female-centric society, and highly tolerant interaction patterns." (Kuroda 1989)
• Adults show high tolerance for young bonobos until they reach puberty around 8 or 9 years.
  • Chimpanzees, by contrast, are often threatened by adult males at the time of weaning.
  • Infanticide in bonobos has never been recorded. (de Waal 1997)
  • Bonobos play "baby" even after weaning by rocking, whimpering, and having temper tantrums.
• More births occur in wild during rainy season.
• Females have been seen nursing two infants of different ages
  • Seen in the wild and at sites where food is provided. (Furuichi & Hashimoto 2002) (Kano 1996)
• Only nutrition for offspring during the first year is from nursing; even though it may mouth solid food, it doesn't eat it.

• Juvenile stage for all great apes lasts longer than that of lesser apes and monkeys.
• Play behavior develops by 2 years.
• Around 3 years can locomote nearly as well as adults but still stay within 10 m (33 ft) of their mothers.
• Around 3 years switch to being carried on the back rather than on the mother's chest.
• Weaning around 4 or 5 years.

• Adult body size reached around 14 to 16 years (at Wamba). (Kuroda 1989)
• Sexual maturity for males assumed to be around 9 years.
  • Males never leave the group of their mother
• Female sexual maturity similar to males'.
  • Females leave their birth groups around 9years.
  • Age of first menstrual cycle in six studied captive females varied between 6 and 9 years. (Vervaecke et al 1999)
  • Age of first pregnancy is usually around 11-13 years.
• Age at female menopause not known, but a 48 year old female at the Frankfort Zoo still had irregular menstrual cycles.. (Jurke et al 2008)

• Around 50 years. (Ankel-Simmons 2000)

• In order to regulate size of captive populations, chimpanzee and bonobo conception is controlled artificially;
• In the U.S. the American Zoo and Aquarium Association Chimpanzee Species Survival Plan regulates breeding. (Lee & Guhad 2001)

• San Diego Zoo's 6,000 sq ft exhibit "Pygmy Chimps at Bonobo Road" opened 4/3/93.
• A second bonobo troop is maintained at the San Diego Zoo's Wild Animal Park.
• The first bonobo to arrive in San Diego was a male, "Kakowet" who was estimated to be 18 months old when he was sent from a Zaire zoo in June, 1960.
• The first pair in the U.S. were seen in San Diego in 1962, when 6 year old female "Linda" was sent from Antwerp Zoo in Belgium.
  • The pair, Kakowet and Linda, produced 3 male and 7 female offspring over 18 years at San Diego.
  • Sperm recovered 6 hours after Kakowet's death from heart failure is kept viable in the "frozen zoo" at the San Diego Zoo's Institute for Conservation Research.
• 58 rescued bonobos live at Lola ya Bonobo, a 30 hectare (74 acre) sanctuary near Kinshasa, Democratic Republic of Congo (2007)
  • This center also obtained access to 20,000 hectares (49,421 acres) of primary tropical forest habitat as a safe place to release rehabilitated bonobos.
• Some 160 Bonobos are kept in zoos in the U.S., England, Belgium, Netherlands and Germany.
• ISIS captive population

• A case of inflammatory heart disease (Encephalomyocarditis virus EMCV) reported for a bonobo in a forest re-introduction program in the Congo Basin. (Jones et al 2004).
• Bonobos are very susceptible to respiratory diseases.
  • Respiratory diseases are the most common causes of death for nonhuman primates. (Adams et al 1995)
  • Tuberculosis is always a threat to nonhuman primates.
• In captive and wild populations:
  • Parasitic infections:
    • Pinworms (Enterobius sp.) are very difficult to eradicate in captive apes.
  • Viruses: Most human viruses can also infect chimpanzees and bonobos
    • They are resistant however to developing clinical AIDS
    • Very susceptible to hepatitis A virus (HAV)
    • The first calicivirus ever isolated from any primate species was found in a San Diego bonobo in the early 1980's
      • Causes inflamation of stomach and intestines in human, may be serious for those with weakened immune systems.
    • A wide range of viruses are transmitted from wild primates to humans, including measles, herpes, Ebola and polio viruses. (Nunn & Altizer 2006) (Whittier 2001)
    • Mosquito-born yellow fever virus is endemic in some African nonhuman primates (Nunn & Altizer 2006)
  • Bacterial infections: many possible, including those that also infect humans - most common are Shigella, Salomonella, Campylobacter, Yersinia.
    • Leprosy (Mycobacterium leprae) is occasionally diagnosed in chimpanzees; a long incubation period means many animals may be infected before the carrier is identified.
  • Fungal infections: Candida is the most common, especially in young and immune-compromised individuals.
    • Colonies housed in southwestern U.S. may suffer from Valley Fever (coccidioidomycosis)
    • Histoplasmosis or Darling's disease may infect colonies in eastern and central U.S.
  • Protozoan infections
    • Giardia and Entamoeba are intestinal parasites
    • More than 20 species of Plasmodium are blood-born parasites transmitted to primates from saliva of biting insects
    • Trypanosoma and Leishmania (some 10 species) also are transmitted from biting insects.
  • Internal parasites - helminth worm infestations
  • External parasites - arthropod (flea and lice) infestation
• Captive individuals who receive good care and have long lives are susceptible to hypertension, obesity, and cardiovascular diseases.
• All chimpanzees and bonobos may suffer bite wounds.

• Wild population estimate: 20,000 - 50,000 (Myers Thompson 1997; Butynski, T. 2001; Dupain & Van Elsacker 2001)
  • Based mainly on nest encounter rates and nest density estimates for these shy animals
  • Southern part of bonobo range in congo Basin still not adequately surveyed (IUCN Redlist 2009); more bonobos may live there
• 1986: IUCN/Species Survival Commission, Primate Specialist Group (Oates 1986) identified conservation and research goals for primates, including bonobos. (Furuichi & Thompson 2008)
• Potential range is estimated at about 500,000 km sq (193,051 mi sq) IUCN Redlist (2009 version) but populations within are not contiguous today and may not have been contiguous in historic times. (Grossmann 2008)
• Listed on Cites Appendix I (2001) as "Endangered"
• IUCN rating of Endangered, Ver. 3.1 Assessed in 2008
• African Convention rating of Class A.
• Bonobos occupy land protected since 2006 in the Faunal Reserve of Lomako-Yokokala and the Tumba-Lediima Natural Reserve. (IUCN 2009)
• Bonobos live in Sankuru Nature Reserve; this new reserve established in 2007
  • Occupies ( 28,490 sq km) 11,000 sq mi
  • Adjoins a proposed Bonobo Peace Forest in central Democratic Republic of the Congo
• Largest protected area in Africa at present (2008) is in Salonga National Park, Congo.
  • Became a National Park in 1970; designated a World Heritage site in 1984
  • Occupies 33,346 sq km (12,875 sq mi)
• A sanctuary established at Lola ya Bonobo near Kinshasa, Democratic Republic of Congo offers care for rescued bonobos and support for conservation efforts. (André et al 2008)
  • Before this sanctuary was established , conservation laws were not able to prevent illegal trade.
  • More bonobos arrived at the sanctuary during a decade of wars, and continued to arrive in greater numbers even after hostilities ceased.
    • Increased awareness by the locals, resumption of forest exploitation, and human population displacements may be factors in the more recent high number of bonobos being confiscated.
  • Education of children and civil servants are important aspects of the bonobo conservation efforts.
  • Planning is underway (as of 2008) for the release into the wild of some captive individuals; although risky, this is one potential tool "to make sure that wild populations remain viable"

• Humans:
  • Until the present, bonobos were protected simply because they occupied areas that were largely isolated from human contact; a developing Congo economy with increasing exploitation of resources plus political instability pose serious threats (Grossmann 2008)
  • Habitat loss due to human population pressures, slash and burn agriculture and commercial forestry.
  • Subsistence hunting for meat (although it is is less of a threat than the commercial hunting)
  • Expansion of the bushmeat trade promoted by lumber companies. (Dupain & Van Elsacker 2001)
  • Occasionally hunted for medicinal or magical purposes (various body parts are used as charms for strength or sexual vitality).
  • Infants are captured by killing the mother and kept as pets or presented as gifts to visiting dignitaries. Infants and juveniles currently sold to zoological gardens and laboratories in Europe and Asia
  • Civil war between 1996-2002 and a weakened National Park system, plus availability of modern weapons all hindered conservation efforts
  • Infectious disease threats from close contact with humans.

• Bonobo Conservation Initiative (BCI): Mission: ensuring survival of the bonobo and its habitat in the Congo Basin. Features conservation projects engaging indigenous Congolese people in cooperative, community-based conservation and development programs.
• Friends of Bonobos: Lola Ya Bonobo sanctuary for confiscated bonobos in Kinshasa. Annual reports document international effort to save bonobos, restore them to native habitats, educate humans about bonobos, promote conservation projects. San Diego Zoo is one of many sponsoring organizations.
• Primate Info Net: Library and Information Service for the National Primate Research Center, University of Wisconsin, Madison.
• African Wildlife Foundation (AWF): African Wildlife seeks to empower Africans to be stewards of the land and resources of Africa.
• Ape Populations, Environments, and Surveys (A.P.E.S.): Extensive database for global distribution and status of great apes. Sponsored by IUCN, SSC, and Arcus Foundation.
• IUCN Red List: Pan paniscus fact sheet.

  ---

  © 2009 San Diego Zoo Global. Last major update 2009; minor update April 2013. Questions may be addressed to kelliott@sandiegozoo.org.

  ---

  Return to the Fact Sheets page