Bonobos

Bonobos

Bonobo

The bonobo (Pan paniscus) is a great ape most closely related to the chimpanzee (Pan troglodytes). The two species are geographically separated by the Congo-Lualaba River in the Democratic Republic of Congo (DRC). The bonobo was originally called the "pygmy chimpanzee," but the term bonobo is used more widely today.

Bonobos live primarily in the rain forests of central DRC. These forests are also home to a diversity of other species, including the forest elephant, many antelope and primate species, and the endemic Congo peafowl. Survival for bonobos and other wildlife is precarious in this country, which is beset by civil war and poverty – factors that indirectly fuel hunting for the bushmeat and ivory trade. 

Bonobos are among humankind’s closest living relatives, they give us insight into the evolution of our own species, and, as seed dispersers, they play an important ecological role in forest regeneration. With possibly fewer than 50,000 bonobos remaining in the wild, they deserve our urgent attention. The bonobo stands as a conservation emblem for DRC’s lowland forest ecosystem.

Range and Ecology

Bonobo range
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Bonobos are confined geographically to a region in DRC known as the Central Congo Basin (Cuvette Centrale), situated south and east of the Congo River, west of the Lualaba River, and north of the Kasai-Sankuru River. Field scientists have identified populations in several locations within the bonobo range. However, not all areas across the range have been surveyed. The most up-to-date and comprehensive information on bonobo occurrence can be found in the Bonobo Conservation Strategy 2012-2022.  Bonobo and chimpanzee ranges are thought to be allopatric – without range overlap. The chimpanzee is found north of the Congo River system.

Bonobos inhabit mature, mixed-species lowland forests located primarily on terra firma, but they can be found in secondary forests, occasionally in seasonally inundated areas, and in the forest of savannah mosaics. They appear to be more arboreal – adapted for living in trees - than other African great apes. They largely eat fruit, leaves, pith, flowers, seeds, nuts, and insects. Sometimes they consume small mammals such as duikers, flying squirrels, and monkeys. Bonobos also have been observed foraging in streams and marshlands.

Bonobo nest
Bonobo nest high in tree canopy

Females can mature by age 9 and usually achieve adulthood between 13 and 14 years of age, around which time they have their first offspring. Bonobo females give birth approximately every four to five years and on average have between four to five young in their lifetime. The average lifespan for bonobos is estimated to be 40 years. In captivity, these ages are slightly different: age at first birth is around 10 years, and bonobos can live up to the age of 65 years.

In captivity, bonobos use tools as readily as chimpanzees, but tool use in wild bonobos is not as elaborate as in wild chimpanzees. Examples of tool use in wild bonobos are: using leaves as cover for rain and brandishing branches in social displays. Almost every night, an adult bonobo makes a new nest for sleeping. Sometimes bonobos make a nest during the day - these are smaller and less sophisticated constructions than night nests. Most nests are in trees, but occasionally bonobos make ground nests (Reinartz et al. 2006).

Social Behavior

Social behavior

Bonobos live in communities comprised of between 10 and 100 individuals. Bonobos are most frequently found in mixed age and sex groups with adults, juveniles and infants of both sexes freely associating with each other. Within a community, bonobos move to form small temporary subgroups. This group fracturing is referred to as fission-fusion dynamics, whereby membership in subgroups often fluctuates, while membership of the larger community rarely changes except for births, deaths, and migrations. Males tend to stay in their natal community, whereas females immigrate and can move to several new communities before settling down. Female status in a group is linked to age, acceptance by other females, and sexual attractiveness.

Having a diverse diet and living in a resource-rich environment are thought to have enabled bonobos to evolve a more relaxed social system relative to chimpanzees and other great apes. In contrast to other apes, female coalitions form the core of bonobo society. 

There is a less pronounced dominance hierarchy in the bonobo's social structure. Bonobos display a greater prevalence of strong female-female bonding as opposed to the predominant male-male bonding observed in chimpanzees. Bonobo society tends to have lower levels of aggression between individual members. Interactions between neighboring communities are reputedly less violent than in chimpanzees and, unlike chimpanzees, bonobos do not appear to patrol the boundaries of their territory. Their generally peaceful society is attributed to the evolution of socio-sexual behaviors.

Sexual behaviors, displayed by bonobos of all ages, have evolved to strengthen group cohesion. For example, mating is common between male and female adults even when the female is not in estrus. There is also a higher frequency of homosexual behavior among bonobos of all ages (especially among adult females), and genital contact functions as social appeasement during times of group tension.

Bonobos communicate using a wide range of vocalizations and gestures. Compared to chimpanzees, bonobos appear to use and combine vocalizations and gestures more flexibly. They hoot over long and short distances, mostly when they arrive at feeding or nesting sites. Vocalizations are also made during feeding, copulation, and in response to danger.

AudioListen to bonobo vocalizations recorded in the Salonga National Park.

Conservation Status

Bonobo nest
Much of the protein consumed in rural areas is meat from wildlife.

Bonobos are listed as endangered by the International Union for Conservation of Nature (IUCN) and designated as CITES Appendix I. It is estimated that there are between 20,000 and 50,000 bonobos remaining in the DRC. Bushmeat hunting is the single greatest threat to bonobos. Conservation in the bonobo’s natural habitat has been limited due to several factors: remote and difficult access to forest landscapes, lack of communication/transportation infrastructure, lack of government support and conservation infrastructure, security risks, and limited funding. A number of national and international organizations continue to promote conservation efforts and the establishment of designated reserves and parks.

Protected areas for bonobos in DRC include the Salonga National Park and four nature reserves, covering approximately 23% of the bonobo historic range. However, in protected areas hunting still occurs. The Bonobo Conservation Strategy 2012-2022 identifies major bonobo population centers and threats within each region, highlights conservation priorities, and recommends specific conservation actions.