Bonobo, Pan paniscus
Geographic Distribution and Habitat
The peaceable bonobo (Pan paniscus) makes its home in the lush rainforests of Central Africa, specifically within the borders of one conflict-ridden country—the Democratic Republic of Congo (DRC). A highly-threatened great ape, the bonobo is confined to a limited, patchwork area comprising in total about 60,000 square miles (about 156,000 sq km). Its range is hemmed geographically by the Congo, Lualaba, and Kasai-Sankuru rivers.
Bonobos thrive in moist, undisturbed old-growth forests, where trees bear fruit throughout the year; however, they can also be found in the montage of secondary forests, seasonally flooded swamp forests, and forest savanna woodlands common to the entire Congo River Basin, itself a rich mosaic of precariously endangered tropical plants and species. There’s a great deal scientists still don’t know about bonobos (research is challenged by their remote habitat, the discontinuity of the species’ distribution, and civil unrest within the DRC), but conservationists are bringing focus to four distinct bonobo strongholds in protected areas in an effort to both better understand and protect the bonobo species.
Size, Weight, and Lifespan
It wasn’t until 1929 that the bonobo earned its distinction as a separate species. As a result, the bonobo has been misunderstood and mislabeled, at times called a pygmy chimpanzee and a dwarf chimpanzee. At two-thirds the size of a human, however, the bonobo is neither diminutive nor a chimpanzee, and much work has been done to distinguish the bonobo from her common chimpanzee (Pan troglodytes) cousin. Weighing in at about 68 lbs (31kg) for females and 86 lbs (39kg) for males, the bonobo is slimmer than a chimpanzee, and at a length of about 35 in (88cm), appears more gracile and elegant.
Adult bonobo males are about 15% larger than their female counterparts. While this is less extreme than the sexual dimorphism seen in other primates, the size difference is significant enough for males to have dominance, similar to male chimpanzees. In bonobo society, however, it is the females who rule, minimizing a need for male aggression and competition.
Bonobos are thought to live to about 20 years old in the wild on average, with some accounts of the oldest bonobo in the wild living to about 50 years. In captivity, bonobos live to about 40 years old.
A society in which the members of a social group break off into smaller groups and then rejoin as a larger group.
Distinct differences in size or appearance between the sexes of an animal in addition to differences between the reproductive organs themselves.
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Many comparisons can and have been made between the bonobo and the chimpanzee, the only two species to make up the Pan genus–and perhaps rightly so. At a cursory glance, the dark-haired bonobo looks similar to a chimpanzee, with long, lanky limbs and nimble, elegant fingers, but a discerning eye can clearly distinguish between the two:
- With a high forehead and deep-set eyes, a bonobo has a small head, small ears, a thin neck, and narrow shoulders.
- Her face is black from birth, whereas the color of a chimpanzee’s face will change over time. She has pink lips and wide-set nostrils.
- With a natural middle part, her hair splays outward in a symmetrical coif. In addition, the bonobo’s hair is not susceptible to the same balding some chimpanzees experience with age.
- She’s born with a white patch on her rump; unlike chimpanzees, the patch does not darken with age.
- Although she is a primarily knuckle-walking quadruped (walking on all fours), she’s far more comfortable walking upright than a chimpanzee, especially when carrying food.
Among bonobos, males have long canine teeth, whereas females lack canines altogether, making the bonobo’s female dominance all the more thought-provoking.
Bonobos get much of their daily fluid intake from fruit, and will forage for leaves, pith, flowers, seeds, nuts, and insects to round out their omnivorous frugivorous diet. Unlike chimpanzees, which will actively hunt monkeys and other mammals, bonobos appear to eat small mammals only when the opportunity arises. Some studies note that bonobos appear to be less fearful of water than chimpanzees, and report bonobos foraging in streams and ponds for shrimp and fish.
Behavior and Lifestyle
With an egalitarian society that emphasizes cooperation and sharing over conflict and territorialism, bonobos are among humans’ closest relatives and yet remain one of the most enigmatic of the great apes. Along with chimpanzees, bonobos share over 98% of their genetic code with humans. Unlike chimpanzees and humans, however, bonobos have never been observed killing one of their own kind.
Scientists suggest that the peaceful nature of bonobo society is related to its unique and sophisticated female-led social structure, which influences all aspects of daily life, from reproduction to socialization to eating. Highly intelligent and seemingly sensitive, bonobos do not appear to have established territories, and conflicts are resolved by using sexual behaviors rather than aggression. Sexual activity also plays an important role in other aspects of bonobo life, including social bonding and for pleasure.
The bonobo’s name has a checkered past. Most believe that the name “bonobo” has no significant meaning, and even may have been a misspelling of a town known as Bolobo, where researchers first found bonobos in the 1920s.
Kanzi, indisputably the world’s most famous bonobo in captivity, is said to have learned over 3,000 English words and can communicate using 348 symbols.
In contrast to other great apes living in Africa, the semi-terrestrial bonobo spends a great deal of time on the ground, yet is particularly well-suited for life in trees. She swings hand to hand through branches, nimbly leaps from tree to tree and climbs tree trunks with aplomb. Active during the day, the diurnal bonobo travels in mixed groups of males, females, and juveniles in a typical fission-fusion pattern. Troop sizes vary from 30 to 100 members, with smaller groups of as few as three to six individuals foraging for food both in the trees and on the ground–often sharing their spoils with each other–and then reuniting with the larger group.
Scientists believe bonobos have high social awareness, even using touch to comfort each other. Researchers also suggest that the accessibility of food within the bonobos’ rich habitat decreases competition among troop members and increases socializing, especially among females.
At night, bonobos gather into larger groups to build nests of leaves and twigs for sleeping, with adults sometimes sharing a nest, a behavior not often seen in other primates. Sleeping in groups allows the bonobos to keep watch for predators. Females and youngsters are the first to retire for the night and make their nests higher in the trees. The males, who have more body mass, sleep lower in the trees, where the branches are thicker. This order also serves to allow the males to protect the more vulnerable members of the troops should an intruder approach from the ground. They build their nests by bending living tree branches inward and interweaving them into large comfortable beds. The nests are large enough that the bonobo is camouflaged from large land predators, like leopards. The branches remain living and unfold back into place the following morning after the bed is abandoned. The tree is unharmed. Bonobos never sleep in the same nest twice.
In the wild, scientists have observed bonobos using tools–such as using leafy branches for rain cover–but not to the same degree as has been observed with chimpanzees. However, tool usage by bonobos in captivity is common, and researchers believe bonobos simply have less need for tool usage in the wild. For example, where chimpanzees may need to use twigs to extract termites from a nest, bonobos do not eat termites and therefore have no need for twig tools.
When it comes to vocalizations, a bonobo’s call can be easily distinguished from the hoots of chimpanzees. His voice is more shrill and uses whooping calls that primatologists have described as sounding like the chorusing yap of small dogs. These high-pitched screams, hoots, barks, and grunts are used to communicate during feeding, sex, and when in danger. A bonobo will hoot over long and short distances, especially when arriving at feeding and nesting areas.
The language also includes hand and foot gestures, along with stares and facial expressions. Pouting lips show disappointment, an open mouth signifies play, and a wide, teeth-showing grin expresses fear.
Bonobos love to touch each other, whether it be in grooming or genito-genital (also referred to as “gg” or genital) rubbing, as such touch behaviors represent an important form of communication and help solidify bonding among troop members. Researchers continue to investigate the use of sexual behavior for non-reproductive purposes, as it is thought to play an important role in the bonobos’ non-aggressive, conflict-averse society.
When a female is old enough, she leaves her troop to find a new one and will mate with males until she gives birth, a rite of passage that awards her permanent membership in a new troop. A male, for his part, is philopatric, and remains with the troop into which he is born, often keeping bonds with his mother for life.
While adult females form strong bonds with each other, bonobos do not form permanent monogamous partnerships. In fact, bonobos have sex with all members of the troop, with no discernment between gender or age. While sexual activity among bonobos is higher than seen in other primates, the rate of reproduction is low.
Bonobos typically reach sexual maturity at six to eight years old, but females don’t give birth until they are about 13. There is no birth season, but a female will give birth every five to six years, allowing her time to bond with her offspring. This is especially true during the first two years of life, when she will carry her infant everywhere. A male inherits the social status of his mother, and is particularly vulnerable without her care.
As with other primates who have a frugivorous diet (fruit-based), bonobos are thought to be important seed dispersers, helping play a critical role in forest regeneration in the fragile Congo River Basin.
The International Union for Conservation of Nature has listed the bonobo as Endangered for the past twenty years (IUCN, 2016). Unfortunately, the bonobo has the distinction of having her habitat solely within the confines of the DRC, where war and poverty create an unstable environment for protecting this great ape.
Although studies of bonobo populations are limited, conservationists believe that there may be as few as 5,000 left in the wild; other reports suggest higher numbers, on the order of 50,000-100,000. All agree, however, that populations have declined significantly in the past 30 years. The IUCN notes that bonobo populations will continue to decline by more than 50% by 2078 if more aggressive conservation actions are not taken.
The two biggest threats to the bonobo are the bushmeat trade and habitat destruction. The IUCN quotes statistics that note an estimated 9 tons of bushmeat are extracted daily from a 19,000 square mile (50,000 sq km) conservation landscape within the bonobo’s range. Taboos that once existed against eating bonobo meat have faded; war and poverty help foster conditions that further promote bushmeat hunting and deforestation.
The Convention on International Trade in Endangered Species of Wild Fauna and Floral (CITES) has included the bonobo on Appendix I, its listing of most endangered wildlife. It is similarly listed as a Class A Endangered Species under the African Convention on the Conservation of Nature and Natural Resources.
A number of organizations and programs have been developed to help the bonobo’s plight, including the Bonobo & Congo Biodiversity Initiative, the Bonobo Conservation Initiative, and the Lola Ya Bonobo Sanctuary. Moreover, the IUCN and ICCN (Congolese Institute for Nature Conservation) have developed a bonobo conservation strategy that outlines five interventions to be undertaken by 2022 within protected bonobo strongholds.
- De Waal, F. Bonobo: The Forgotten Ape. Berkeley and Los Angeles: University of California Press: 1997. Print.
- Furuichi, T. (2011), Female contributions to the peaceful nature of bonobo society. Evol. Anthropol., 20: 131–142. doi:10.1002/evan.20308
- Graham, K.E., Furuichi, T. & Byrne, R.W. Anim Cogn (2017) 20: 171.
Written by Christine Regan Davi, October 2017