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Bonobo (Pan paniscus) Fact Sheet: Behavior & Ecology

Bonobo (Pan paniscus)

Activity Cycle

General

  • 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.

Daily patterns

  • 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.

Social Groups

General

  • 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 colonies under managed care.
    • Both colonies characterized as peaceful, egalitarian, and female dominated.
    • Stevens et al (2008) caution that all bonobos in managed care 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)

Hierarchy and bonding (Stevens et al 2008) (de Waal 1995, 1997) (Parish 1993, 1996)

  • A study by Stevens et al (2008) found bonding patterns in four managed care 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.
      • Female bonobos in managed care 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 bonobo populations in managed care, 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

Territorial Behavior

  • 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.

Social Interactions

Sociosexual behavior (de Waal 1988, 1995, 1997, 2001) (Paoli et al 2006)

  • 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).

Communication

Gesture (Pollick et al 2008) (de Waal 2001)

  • 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.

Vocalizations (Pollick et al. 2008)

  • 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"

Locomotion

  • 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)

Other Behaviors

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)
    • Bonobos in managed care 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.

Communication Through Touch

two bonobos touching

Bonobos forge strong social bonds using tactile and visual communication.

Image credit: © San Diego Zoo Global. All rights reserved.

 

Page Citations

Anderson et al. (2002)
Boesch & Boesch-Achermann (2000)
Corballis (2002)
Enomoto (1990)
Goodall (1986)
Hohmann & Fruth (2002)
Idani (1995)
Kano (1992)
Kano et al. (1996)
Kuroda (1989)
Matsuzawa (2000)
Palagi & Paoli (2008)
Parish (1993, 1996)
Pollick & de Waal (2004)
Pollick et al. (2008)
Stevens et al. (2008)
de Waal (1995, 1997, 2001)
Watts (1998)
White & Chapman (1994)
White & Waller (2008)

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