Bonobo (Pan paniscus) Fact Sheet: Behavior & Ecology

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.

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 managed care may be a side effect of life in managed care. (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 managed care 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

• 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.

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).

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"

• 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)
  • Bonobos in managed care played more during times before feeding, perhaps because they anticipate tension.
• Bonobos in managed care 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.

Bonobos forge strong social bonds using tactile and visual communication.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

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)