Bonobo

The bonobo (; Pan paniscus), also historically called the pygmy chimpanzee (less often the dwarf chimpanzee or gracile chimpanzee), is the smallest species of great ape and one of the two making up the genus Pan (the other being the common chimpanzee, Pan troglodytes). While bonobos are today recognized as a distinct species, they were initially thought to be a subspecies of Pan troglodytes, because of the physical similarities between the two species. Taxonomically, members of the chimpanzee/bonobo subtribe Panina—composed entirely by the genus Pan—are collectively termed panins. Bonobos are distinguished from common chimpanzees by relatively long limbs, pinker lips, a darker face, a tai...

Bonobos are found only south of the Congo River and north of the Kasai River (a tributary of the Congo), in the humid forests of the Democratic Republic of Congo. Ernst Schwarz's 1927 paper "Le Chimpanzé de la Rive Gauche du Congo", announcing his discovery, has been read as an association between the Parisian Left Bank and the left bank of the Congo River; the bohemian culture in Paris, and an unconventional ape in the Congo. The ranges of bonobos and chimpanzees are separated by the Congo River, with bonobos living to its south and chimpanzees to the north.

Democratic Republic of the Congo

The bonobo is an omnivorous frugivore; 57% of its diet is fruit, but this is supplemented with leaves, honey, eggs, meat from small vertebrates such as anomalures, flying squirrels and duikers, and invertebrates. The truffle species Hysterangium bonobo is eaten by bonobos. In some instances, bonobos have been shown to consume lower-order primates. Some claim bonobos have also been known to practise cannibalism in captivity, a claim disputed by others. However, at least one confirmed report of cannibalism in the wild of a dead infant was described in 2008. A 2016 paper reported two more instances of infant cannibalism, although it was not confirmed if infanticide was involved.

Primatologist Frans de Waal states bonobos are capable of altruism, compassion, empathy, kindness, patience, and sensitivity, and described "bonobo society" as a "gynecocracy" (i.e. a matriarchy). Primatologists who have studied bonobos in the wild have documented a wide range of behaviours, including aggressive behaviour and more cyclic sexual behaviour similar to chimpanzees, even though bonobos show more sexual behaviour in a greater variety of relationships. An analysis of female bonding among wild bonobos by Takeshi Furuichi stresses female sexuality and shows how female bonobos spend much more time in oestrus than female chimpanzees. Some primatologists have argued that De Waal's data reflect only the behaviour of captive bonobos, suggesting that wild bonobos show levels of aggression closer to what is found among chimpanzees. De Waal has responded that the contrast in temperament between bonobos and chimpanzees observed in captivity is meaningful, because it controls for the influence of environment. The two species behave quite differently even if kept under identical conditions. A 2014 study also found bonobos to be less aggressive than chimpanzees, particularly eastern chimpanzees. The authors argued that the relative peacefulness of western chimpanzees and bonobos was primarily due to ecological factors. Bonobos warn each other of danger less efficiently than chimpanzees in the same situation. Nonetheless, in April 2024, biologists reported that bonobos behave more aggressively than thought earlier. In a study published in February 2025, scientists determined that bonobos could tell when humans did not know something. The findings advance researchers' proposal that like humans, chimpanzees and bonobos—humans' closest evolutionary cousins—may also possess theory of mind.

The bonobo was first recognised as a distinct taxon in 1928 by German anatomist Ernst Schwarz, based on a skull in the Tervuren Museum in Belgium which had previously been classified as a juvenile chimpanzee (Pan troglodytes). Schwarz published his findings in 1929, classifying the bonobo as a subspecies of chimpanzee, Pan satyrus paniscus. In 1933, American anatomist Harold Coolidge elevated it to species status. Major behavioural differences between bonobos and chimpanzees were first discussed in detail by Tratz and Heck in the early 1950s. Unaware of any taxonomic distinction with the common chimpanzee, American psychologist and primatologist Robert Yerkes had already noticed an unexpected major behavioural difference in the 1920s. Bonobos and chimpanzees are the two species which make up the genus Pan, and are the closest living relatives to humans (Homo sapiens). Bonobos and common chimpanzees show remarkable evolutionary stasis in musculoskeletal anatomy since their split from humans 8 million years ago, with bonobos exhibiting no changes since diverging from common chimps ~2 million years ago, making them a better anatomical model for the last common ancestor of humans and chimps/bonobos. Nonetheless, the exact timing of the Pan–Homo last common ancestor is contentious, but DNA comparison suggests continual interbreeding between ancestral Pan and Homo groups, post-divergence, until about 4 million years ago. DNA evidence suggests the bonobo and common chimpanzee species diverged approximately 890,000–860,000 years ago following separation of these two populations possibly because of acidification and the spread of savannas at this time. Currently, these two species are separated by the Congo River, which had existed well before the divergence date, though ancestral Pan may have dispersed across the river using corridors which no longer exist. The first Pan fossils were reported in 2005 from the Middle Pleistocene (after the bonobo–chimpanzee split) of Kenya, alongside early Homo fossils. According to A. Zihlman, bonobo body proportions closely resemble those of Australopithecus, leading evolutionary biologist Jeremy Griffith to suggest that bonobos may be a living example of our distant human ancestors. According to Australian anthropologists Gary Clark and Maciej Henneberg, human ancestors went through a bonobo-like phase featuring reduced aggression and associated anatomical changes, exemplified in Ardipithecus ramidus. The first official publication of the sequencing and assembly of the bonobo genome was released in June 2012. The genome of a female bonobo from Leipzig Zoo was deposited with the International Nucleotide Sequence Database Collaboration (DDBJ/EMBL/GenBank) under the EMBL accession number AJFE01000000 after a previous analysis by the National Human Genome Research Institute confirmed that the bonobo genome is about 0.4% divergent from the chimpanzee genome. The bonobo is commonly considered to be more gracile than the common chimpanzee. Although large male chimpanzees can exceed any bonobo in bulk and weight, the two species broadly overlap in body size. Adult female bonobos are somewhat smaller than adult males. Body mass ranges from 34 to 60 kg (75 to 132 lb) with an average weight of 45 kilograms (99 lb) in males against an average of 33 kg (73 lb) in females. The total length of bonobos (from the nose to the rump while on all fours) is 70 to 83 cm (28 to 33 in). Male bonobos average 119 cm (3.90 ft) when standing upright, compared to 111 centimetres (3.64 ft) in females. The bonobo's head is relatively smaller than that of the common chimpanzee with less prominent brow ridges above the eyes. It has a black face with pink lips, small ears, wide nostrils, and long hair on its head that forms a parting. Females have slightly more prominent breasts, in contrast to the flat breasts of other female apes, although not so prominent as those of humans. The bonobo also has a slim upper body, narrow shoulders…

Researchers have found that both central (Pan troglodytes troglodytes) and eastern chimpanzees (Pan troglodytes schweinfurthii) share more genetic material with bonobos than other chimpanzee subspecies. It is believed that genetic admixture has occurred at least two times within the past 550,000 years. In modern times hybridization between bonobos and chimpanzees in the wild is prevented as populations are allopatric and kept isolated on different sides of the Congo river. Within captivity, hybrids between bonobos and chimpanzees have been recorded. Between 1990 and 1992, five pregnancies were conceived and studied between a male bonobo and two female chimpanzees. The two initial pregnancies were aborted because of environmental stressors. The following three pregnancies however led to the birth of three hybrid offspring. A bonobo and chimpanzee hybrid called Tiby was also featured in the 2017 Swedish film The Square. This same male bonobo and female chimpanzee had several offspring.

The IUCN Red List classifies bonobos as an endangered species, with conservative population estimates ranging from 29,500 to 50,000 individuals. Major threats to bonobo populations include habitat loss and hunting for bushmeat, the latter activity having increased dramatically during the first and second Congo Wars in the Democratic Republic of Congo, due to the presence of heavily armed militias (even in remote, "protected" areas such as Salonga National Park). This is part of a more general trend of ape extinction. As the bonobos' habitat is shared with many people, the ultimate success of conservation efforts still relies on local and community involvement. The issue of parks versus people is salient in the Cuvette Centrale, within the bonobos' range. There is strong local, and broad-based Congolese, resistance to establishing national parks, as indigenous communities have previously been driven from their forest homes by the forming of parks. In Salonga National Park (the only national park in bonobo habitat), there is no local involvement, and surveys undertaken since 2000 indicate the bonobo, the African forest elephant, the okapi, and other rare species have been devastated by poachers and the thriving bushmeat trade. In contrast, areas do exist where the bonobo and ecological biodiversity still thrive without any established park borders, because of the indigenous beliefs/taboos against killing bonobos and other animals. During the wars in the 1990s, researchers and international non-governmental organisations (NGOs) were driven out of the bonobo habitat. In 2002, the Bonobo Conservation Initiative initiated the Bonobo Peace Forest Project (supported by the Global Conservation Fund of Conservation International), in cooperation with national institutions, local NGOs, and local communities; the Peace Forest Project works with local communities to establish a linked constellation of community-based reserves managed by local and indigenous people. This model, implemented mainly through DRC organisations and local communities, has helped bring about agreements to protect over 50,000 square miles (130,000 km2) of the bonobo habitat. According to Amy Parish, the Bonobo Peace Forest "is going to be a model for conservation in the 21st century". The port town of Basankusu is situated on the Lulonga River, at the confluence of the Lopori and Maringa Rivers, in the north of the country, making it well placed to receive and transport local goods to the cities of Mbandaka and Kinshasa. With Basankusu being the last port of substance before the wilderness of the Lopori Basin and the Lomako River—the bonobo heartland—conservation efforts for the bonobo use the town as a base. In 1995, concern over declining numbers of bonobos in the wild led the Zoological Society of Milwaukee (ZSM), in Milwaukee, Wisconsin, with contributions from bonobo scientists around the world, to publish the Action Plan for Pan paniscus: A Report on Free Ranging Populations and Proposals for their Preservation. The Action Plan compiles population data on bonobos from 20 years of research conducted at various sites throughout the bonobo's range. The plan identifies priority actions for bonobo conservation and serves as a reference for developing conservation programs for researchers, government officials, and donor agencies. Acting on Action Plan recommendations, the ZSM developed the Bonobo and Congo Biodiversity Initiative. This program includes habitat and rain-forest preservation, training for Congolese nationals and conservation institutions, wildlife population assessment and monitoring, and education. The ZSM has conducted regional surveys within the range of the bonobo in conjunction with training Congolese researchers in survey methodology and biodiversity monitoring. The ZSM's initial goal was to survey Salonga National Park to determine the conservation status of the bonobo within the park and to provide financial and technical assistance to streng…

Formerly the bonobo was known as the "pygmy chimpanzee", despite the bonobo having a similar body size to the common chimpanzee. The name "pygmy" was given by the German zoologist Ernst Schwarz in 1929, who classified the species on the basis of a previously mislabeled bonobo cranium, noting its diminutive size compared to chimpanzee skulls. The name "bonobo" first appeared in 1954, when Austrian zoologist Eduard Paul Tratz and German biologist Heinz Heck proposed it as a new and separate generic term for pygmy chimpanzees. The name is thought to derive from a misspelling on a shipping crate from the town of Bolobo on the Congo River near the location from which the first bonobo specimens were collected in the 1920s. In English the word is generally stressed on the second syllable, in both the US and UK, though sometimes it is instead stressed on the first syllable.