One Life: Bonobos

14 February 2022

Wild bonobos can only be found in forests south of the Congo River in the Democratic Republic of Congo. Sometimes known as the pygmy chimpanzee, bonobos weren’t recognised as a separate species until 1929.

Bonobos and chimpanzees share 98.7% of their DNA with humans — making the two species our closest living relatives.

Bonobos are very social

Bonobos live in close family groups, the family is led by the females and individuals within the family, develop strong bonds and friendships, grooming each other and helping others within their group to find food to ensure that all members of the group are well fed and healthy.

Bonobo group

Bonobos are empathic and peaceful

While humans and chimpanzees display empathy, both species also wage war and kill each other, bonobos do not, in fact there has never been a recorded case in captivity or in the wild of a bonobo killing another bonobo.

They live in a society virtually without violence, and one way they deal with conflict and tension is to have sex. Whenever things get tense in the bonobo world, they'll usually have some kind of sociosexual activity and this seems to really help everybody get along.

They are also naturally more tolerant, they share more, and if an individual gets upset, it's not just sex they use to calm thngs down they also like a hug to comfort one another.

The bonobos' generous nature likely evolved because they live in an area of the Congo where food is plentiful, never having to compete with gorillas or kill for a meal like chimpanzees do.

Cooperative

Due to their social nature, bonobos are highly cooperative.

In behavioural research experiments individuals cooperate ( by simultaneously pulling a rope) to retrieve and share food that was not easily divisible — that is, food that might be easily monopolized by one of the two individuals.

Cooperative with known and unknown individuals

They will also cooperate with strangers to perform tasks such as locating food even when there is no immediate payback, and without having to be asked first.

bonobo cooperation

In one experiment, sixteen bonobos were led one at a time into one of two adjacent rooms separated by a fence. The researchers hung a piece of apple from a rope just above the empty room, visible but out of reach. The apes couldn't access the fruit or the rope. But if they climbed the fence they could reach a wooden pin holding the rope to the ceiling and release the dangling fruit, causing it to drop within reach of any bonobo that entered the next room.

The bonobos released the fruit roughly four times more often when an unfamiliar bonobo was in the adjacent room than when the room was empty. What's more, the bonobos didn't wait to be asked for help, they just offered it.

The impulse to be nice to strangers is likely to have evolved as the benefits of bonding with outsiders outweigh the costs.

Bonobos are willing to share food with individuals within and outside their own family groups, and individuals from different social groups take part in grooming and sexual activities, helping to strengthen bonds and mitigate aggression.

Develop powerful allies

Whilst bonobo societies are built on friendship and cooperation, it still pays for individuals to develop allies with those that have a higher social ranking to ensure they have access to resources and protection within their family groups. This may mean choosing to associate with individuals that may be more selfish than others to gain such protection.

Build and sometimes ‘share’ nests

Bonobos build night-time nests made of leaves and twigs, in the forks of trees each evening. They build these close together to help each other look out for predators such as leopards and snakes. Adult bonobos sometimes share a nest, which is a unique behaviour among the great apes.

Are great parents

Bonobos are perfect mums, their infants are born virtually helpless and must be carried everywhere by their mothers for the first two years. At birth, the male bonobo inherits the social status of his mother and relies on her for protection. He shares a close, permanent bond with her and remains with her throughout his life. Both male and female youngsters stay close to Mom for several years while they grow and learn how to be a part of bonobo society. The mother gives birth every five to six years, allowing her plenty of time to bond with each offspring.

Love to play

Playing is a part of growing up, as the young bonobos gain independence and test their skills against each other. The youngsters play games with each other as they develop their social skills and have fun.

Bonobos ‘babysit’

Bonobo females support mums by babysitting and caring for their infants and in the process acquiring maternal skills and forging alliances that are likely to help them in later life.

Females approach the mothers, groom them briefly and then carry the babies away and engage in nurturing and other maternal behaviours, such as grooming and cradling them, putting them on their belly and carrying them on their back.

Females also show elevated levels of oxytocin—associated with complex social behaviours and social cognition, including maternal and caregiving activities—present in urine samples collected after infant-handling activities. As young females interact with the infants, increased oxytocin may reflect how the body reinforces caregiving activity or social bonding with mothers or infants.

This behaviour reaps further reward for young female bonobos, as mothers  often come to the aid of younger females that had handled their infants when conflicts arise within the group.

Support each other during childbirth

Researchers have observed captive bonobo females coming together when an individual is giving birth, guarding the female and preventing males from coming close, swatting flies away from a female's exposed genitals and even catching and handling  the baby as it is delivered.

This behaviour is more evident in females that have already given birth themselves and thus have some idea of how to help.

Adopt infants outside of their social group

Bonobo groups in the Wamba area of the Democratic Republic of Congo have been observed adopting and raising infants from outside of their immediate social group. Examples include Chio, an older female in her 50’s who adopted three-year-old Ruby from an unknown group, and Marie, an 18-year-old who adopted a two and a half year old Flora after her mother disappeared from a separate group.

Neither Chio nor Marie, who had already had their own offspring, had any pre-existing family connections to the adopted infants or any strong social connections with the youngsters' biological mothers, yet both readily adopted the young bonobos. Both adoptive mothers carried, groomed, nursed, and shared food with their adopted young. Ruby and Flora were also both observed suckling at their adopted mothers. In the case of Ruby, she might have been suckling for comfort as Chio is unlikely to have been producing milk.

Usually in wild animals adoptive mothers are related to orphaned infants or sometimes young females will adopt orphans to improve their own care-giving behaviours, which increases the future survival chances of their own offspring. This means that adoption in non-human animals can usually be explained by the adoptive mother's own self-interest or pre-existing social relationships.

These adoptions appear to be carried out for pure selfless concern for others and an emotional desire to offer care to individuals that the adoptive mothers have no previous connection with.

Females band together

Older female bonobos frequently aid younger females when males behave aggressively towards them, helping them to maintain a superior status in bonobo society.

For bonobos, females leave their birth group during adolescence, so females in a group are generally non-relative to each other. Despite this, they frequently form coalitions to ensure they have access to resources and defend themselves against harassing males.

Young females have a lower social status than males, but protection from older females seems to let young females join the group without fear of being attacked by males. By controlling aggression by males in this manner, females maintain overall superiority in the social hierarchy.

The older females also benefit as the younger females spend more time with them in hopes of getting protection. This way, the older females can give their sons more opportunities to mate with the younger females.

Committed to social interactions

Bonobos, when abruptly interrupted in a social activity with another bonobo, resume it as soon as the interruption is over with the same partner. In humans, joint commitment to an activity is the sense of mutual obligation we feel toward each other when we do things together, such as sharing a meal. But if one person is interrupted in this activity, by the ringing of a phone, for example, they will not just walk away, but will apologise. Then, when the phone call is over, the two partners in the interrupted interaction resume their discussion where they left off.

In bonobos, joint commitment is verified through grooming. Experiments involved observing a group of bonobos engaged in such activities and then emitting either a loud sound to disperse the group  or calling only one bonobo by name.

Results show that after a few minutes of interruption, the bonobos resumed the social activity they had started with the same partner, and they produced communication signals to both suspend and resume interaction.

Mums help their sons

Bonobo mothers actively take action to ensure their sons will become fathers, and in doing so increase their sons' chance of fatherhood three-fold. Bonobo mothers advocate for their sons in male-on-male conflicts, and they will both protect their sons' when they make mating attempts from other males and will also intervene in other male's mating attempts to reduce their chances of success.

The bonobo mums also use their rank in the bonobo's matriarchal society to give their sons access to popular spots within social groups in the community and help them achieve higher male status -- and therefore, better mating opportunities.

Interestingly, bonobo moms do not appear to extend similar help to their daughters, nor have there been any observations of daughters receiving assistance in rearing their offspring. In bonobo social systems, the daughters disperse from the native community and the sons stay.

This helps older females to increase their reproductive success without having more offspring themselves.

Communicators

Bonobos communicate vocally and with a wide variety of gestures that others within their family group understand.

Bonobos families often separate into smaller groups during foraging and they use calls to communicate with each other and to let each other know their whereabouts. Females leave their original community but may continue to interact with their old companions in subsequent meetings between communities.  So, effective social navigation depends on the ability to recognise social partners past and present.

Can remember the voices of old friends

Bonobos can remember the voices of old friends for several years, and when recordings are played to them they become excited and search for the individuals they remember.

Bonobos, like many other primate species, including humans, form complex social networks where remembering "who is who" is important, sometimes vital.  These social associations need recognition between members of the groups – usually via faces and voices.

Communicators with context

Bonobo gestures change meaning according to the specific context in which they are used, in the same way humans communicate. with some gestures having multiple meanings depending on specific contextual settings.

For example, if a  bonobo raises her arm and another comes to clean bits out of her hair, then the meaning is something like 'please groom me.' But some types of gestures get a variety of different responses. For example, an  arm raise gesture sometimes means 'please carry me' or 'let's mate', and the meaning is dependent upon the specific context of the situation that the individuals are in.

EMPATHY

Bonobos also communicate in a similar manner to human infants, using a high-pitched call, or 'peep', that requires context to be understood. The 'peep' calls are short, very high-pitched and produced with a closed mouth, and they are produced in a wide range of situations, across positive, negative and neutral circumstances, when feeding, travelling and resting.

Because they are used in so many circumstances, it is necessary for individuals to understand the context and emotional states of individuals to understand the meaning.

Communicate cooperatively

Communicative exchanges in bonobos resemble cooperative turn-taking sequences  in human conversation. For bonobos, gaze also plays an important role and they seem to anticipate signals before they have been fully articulated. Communicative interactions of bonobos thus show the hallmarks of human social action during conversation and suggest that cooperative communication arose as a way of coordinating collaborative activities more efficiently.

Communicate using referential gestures

To solve social conflicts female bonobos invite other females to engage in a socio-sexual behaviour by using pointing gestures and mimicking hip swings. Referential gesturing, such as pointing, and forms of iconic gesturing, such as pantomime, have been observed in wild bonobos.

The gestures used by the females are notable in that they appear to be not only intentional, but also referential and potentially iconic, since they communicate specific information about the desired goal.

Experience disgust

Bonobos have a sense of disgust with regards to food that is presented to them that smells bad or is presented to them close to faeces, demonstrating a sensitivity to the signs of pathogens in food that they are at risk of ingesting.

They are also less likely to engage in exploratory activities like touching and tasting substrates, or even using tools to achieve a goal when confronted with 'bad' smells.

This ‘disgust’ response is more developed in adults than in juveniles and infants suggesting that eating contaminated foods in childhood may help them build their immune systems at a critical time in their development.

Good problem solvers and tool-users

Bonobos are efficient tool-users, using stones to crack nuts and are able to plan and carry out a task using many different tools to reach a food reward, using  modified branches and unmodified antlers or stones to dig under rocks and in the ground to retrieve food.

They have also demonstrated the ability to learn how to make tools and subsequently develop their own tools for more complex tasks such as breaking wooden logs and to dig underground.

Bonobos use rocks as hammers or projectiles to smash their targets, and rotate stone flakes to serve as drills or use the flakes as scrapers, axes or wedges to attack slits, the weakest areas of logs, to break them. To root into hard soil, bonobos use both unmodified rocks and a variety of handmade stone tools as shovels.

TOOLS

Understand that some things are all in your head

The capacity to tell when others hold mistaken beliefs is seen as a key milestone in human cognitive development. Humans develop this awareness in early childhood, usually before the age of five. It marks the beginning of a young child's ability to fully comprehend the thoughts and emotions of others—what psychologists call theory of mind.

Such skills are essential for getting along with other people and predicting what they might do. They also underlie our ability to trick people into believing something that isn't true.

Understanding that beliefs may be false requires grasping, on some level, that not all things inside our heads are real. It means understanding that there exists a mental world distinct from the physical world.

This ability has been demonstrated in Bonobos, with the ability to understand that others may have different information in their heads than they hold themselves.

In a research study, individuals watched two short videos. In one, a person in a King Kong suit hides himself in one of two large haystacks while a man watches. Then the man disappears through a door, and while no one is looking, King Kong runs away. In the final scene the man reappears and tries to find King Kong.

The second video is similar, except that the man returns to the scene to retrieve a stone he saw King Kong hide in one of two boxes. But King Kong has stolen it behind the man's back and made a getaway.

The researchers teased out what the apes were thinking while they watched the movies by following their gaze with an infrared eye-tracker installed outside their enclosures.

To pass the test, the apes must predict that when the man returns, he will mistakenly look for the object where he last saw it, even though they themselves know it is no longer there. In both cases, the apes stared first and longest at the location where the man last saw the object, suggesting they expected him to believe it was still hidden in that spot.

In a second test a person placed an object in one of two boxes. Another person then took this object out of this box, put it into another box, and locked both boxes. For the true belief condition, the first person stayed in the room—so this person knew where the object was and thus had a true belief. For the false belief condition, however, the first person was out of the room during the switch —so while he thought he knew where the object was, he was mistaken and thus had a false belief. In both conditions, the first person tried to open the box he originally had put his object in. The bonobos knew how to unlock the boxes, and could decide which box to open for the first person during the test.

The researchers found that, like human infants, bonobos were more likely to help the person find the object when he had a false belief about which box the object was in. This suggests they  understand the person's beliefs about reality to decide how to help him.

Bonobos really are amazing animals!

Bonobo conservation

Bonobos are classified as ‘endangered’ due to their low population numbers in the wild, and these populations are threatened by both habitat loss and poaching.

Humans hunt bonobos to eat them, trade them as bushmeat, keep them as pets and for use in traditional medicine. Specific bonobo body parts are believed to enhance sexual vigor or strength. The number of bonobos lost to poaching each year is not known, but the number of bonobo charms available in parts of the Democratic Republic of Congo suggests that poaching may be common.

Only part of the bonobo’s range lies in protected areas. A growing and moving human population, combined with slash-and-burn agriculture and commercial logging, leaves bonobos outside protected parks at risk of losing their homes.

Civil unrest in the region around the bonobo’s home territory has led to many bonobo deaths, as gangs of poachers have been free to invade Salonga National Park, one of few protected areas for bonobos. In addition, unrest has made modern weaponry and ammunition more available, enabling hunting, and the military has at times sanctioned the hunting and killing of bonobos.

For more information about bonobo conservation and sanctuary:
Friends of Bonobos
Bonobo Conservation Initiative
 
Read more:
One Life: Chimpanzees
One Life: Orangutans


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