Bonobo, Pan paniscus
BONOBO
Pan paniscus
Geographic Distribution and Habitat
Bonobos live in central Africa, south of the Congo River. The river separates them from their genetic relatives, the chimpanzees (Pan troglodytes). Bonobos live in dense forests with trees of different heights, and they can even be found in swamp forests that flood during the rainy season.
Most of what we know about wild bonobos comes from two areas in the Democratic Republic of the Congo (DRC): the Lamako and Wamba sites. The dense forest home of the bonobo is extremely difficult to access with areas that are flooded. Diseases like malaria and yellow fever are known hazards to human exploration and settlements. These challenges limit the number of researchers that can study wildlife here. More limiting than these natural conditions is the fact that this region of Africa has been conflicted by war and colonialism since the late 20th century. The political instability has made conservation and research a low priority compared to people’s safety and food security.
Bonobos were first incorrectly considered to be a subspecies of chimpanzees and were even known as “pygmy chimpanzees.” This confusion most likely came from the physical similarities between young bonobos and chimpanzees and their close geographical proximity. But adult bonobos are smaller than adult chimpanzees. Genetic studies have shown that chimpanzees and bonobos are distinct but closely related species. Both bonobo and chimpanzee genetics are closely related to human genetics (more than 98% of our genes are similar to these primates). And if you were to see bonobos moving, sitting, and eating fruit you can definitely see the similarity to how humans behave.
Size, Weight, and Lifespan
The average bonobo is about as tall as a human toddler and typically measures around 3 feet (91 cm) tall. However, when male bonobos stand fully upright, some may be closer to 4 feet (121 cm) tall.
An average adult male weighs 80–90 pounds (36–43 kg) and an average female weighs 57–80 pounds (26–36 kg). They can live 45–50 years in the wild.
Appearance
Unlike their more famous relatives, the chimpanzees, bonobos have a smaller head, slender (gracile) build, and a more upright posture. Bonobos have more hair around their head with long whiskers on their cheeks. Their hair falls straight on either side of their head in a middle part, almost as if they styled it that way. They have black faces, pink lips, and large brown eyes that peer out curiously at their world.
Bonobos, like other great apes, have opposable thumbs and an opposable big toe. Some adult bonobos have a white tuft of hair on their tail, called a pygal tail tuft, that is usually found only in the young of other African ape species (gorillas and chimpanzees).
Female bonobos have genital swellings, which may indicate that they are ready to mate or receive sexual attention. These pink swellings can last for 13 days and, during this time, the female gets more attention from both males and females.
Males have slightly larger canine teeth than females, which are only visible when their mouths are open. These canines are not as large as those of chimpanzees.
Sexual dimorphism, or the visual differences between males and females, is lesser than that of other great apes. Females have genital swellings and males can be heavier than females. However, in a wild community with bonobos of different ages, it can be difficult to differentiate between sexes at a glance, unlike with gorillas and chimpanzees.
If you watch a bonobo, you can easily see how we are genetic relatives. Bonobos have many common and relatable gestures, such as pouting their lips when they are displeased or shaking their head when they do not want to do something. For many animals, like deer or monkeys, humans have a difficult time identifying individuals by their faces. Bonobos’ facial features are distinct enough that researchers can distinguish most individuals after spending time observing them. Differentiating between individual bonobos in a group has made it easier to conduct behavioral and social studies on wild bonobo populations.
Diet
Bonobos are omnivores. Fruits, shrubs, leaves, fungi, insects, and flowers form the main part of their diet. Bonobos will even swim out into flooded regions to reach fruits, flowers, or minerals that are nutritious. Recently, a group of bonobos was observed hunting small antelopes and sharing the kill with their group! However, hunting is rare.
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 pleasure.
Bonobos are diurnal (active during the day) and semi-terrestrial (44% of their time is spent in trees and 56% on the ground). They climb trees to access ripe fruits and to create safe sleeping sites.
During the day, they spend 35–61% of their time foraging for food, 13–37% resting, and 15–25% traveling. They can travel quickly through the forest as they move from one food source to another, especially when trees are in fruiting season. They share their food with other bonobos even if they do not know them. This selflessness, or altruism, is another reason that these great apes are special.
Bonobos rest when temperatures are high and travel to their sleeping sites before nightfall. Preparing for the night can be an elaborate affair in which they collect leaves and branches from different trees to make cozy nests for the group
In captivity, bonobos have famously used tools, including making stone tools and lighting a fire. However, in the wild, their tool use is less frequent. This is probably because their rich environment provides them with enough easily accessed food sources so that they do not have to use implements to break open ant nests or scoop insects out from hard-to-reach places.
Bonobos are known for their non-violent, female-dominant societies, which is rare among apes.
Unrelated females form strong bonds and band against males that become aggressive towards a female.
They share 98% of their genetic material with humans.
Bonobos are capable of learning complex tasks and using tools.
Every night, bonobos make nests out of leaves and sometimes use leaves as blankets and hats to keep dry.
Bonobos are one of the biggest seed dispersers and have an important role in forest regeneration.
Bonobos are truly remarkable apes who look at their environment and see opportunities and solutions to their problems. They typically resolve conflicts peacefully. Since aggression can lead to injury, peaceful resolutions are the best option for remaining unharmed, especially when there are plenty of resources for everyone. Bonobo habitats are abundant with fruits and other favored dietary items. As omnivores, they can eat a wide variety of foods. This might explain why bonobos find it more beneficial to peacefully share their resources rather than fight over them.
Bonobos have a multi-male, multi-female, fission-fusion type social organization in which group size and composition (ratio of males, females, and juveniles) change depending on the habitat and availability of resources. Therefore their communities, or troop sizes, are not consistent.
Larger communities of bonobos can break off into smaller groups referred to as “parties.” This is the fission part of the fission-fusion social structure. These parties can consist of all males, females (including young male offspring), or mixed parties of adult males and females. Individuals may choose to join or leave parties as a result of social and environmental pressures.
Once a female party is established, its members tend to stay in their parties, spending time in the company of other females, and creating a dominance hierarchy that keeps outside male aggression in check. Therefore, their social organization is driven by the number of and interactions between females. In female-based parties, researchers have observed more affectionate or affiliative associations.
Male-male interactions can be more aggressive. In all-male parties, the larger males tend to be the dominant members of their group. Their dominance does not carry over when they engage with female parties, however. Female parties are female-centric, with the eldest being the matriarch. The males who are more dominant within their groups are more likely to attempt to infiltrate a female party for mating. If the females are uninterested, they are more than capable of repelling or fighting off any males. It is interesting to note that, in bonobo societies, males are compliant and follow the preferences of the females.
That said, bonobos do not appear to have established territories, and conflicts are frequently 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 pleasure.
Initiation of sex is one type of affiliative behavior between party members, particularly among females. Bonobos engage in sexual behaviors as a method of reducing tension in groups and sometimes in exchange for food. Same-sex interactions occur frequently between females. Female bonobos depend on the strong bonds they form with other females in their party to help care for their young and to maintain peace when males become too aggressive.
At night, bonobos gather into larger groups—this is the fusion part of the fission-fusion social structure—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 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.
If they are in a hurry, they can even pull together a quick nest in four minutes. They may use larger leaves as blankets or hats to keep warm and dry in inclement weather conditions.
In the wild, bonobos communicate using many vocal, visual, and tactile signals. Many of their gestural signs seem to be similar to what humans would use, such as shaking their heads to say “no.”
Bonobos are highly social, and spend a lot of time in close contact with party members. They embrace, groom, and engage in non-reproductive sexual contact to communicate with each other, which increases the strength of their social bonds or a sense of closeness between groups.
Bonobos use an agitated, whooping long-distance call as they travel through the forest. This may be a contact call to keep the group together, but its function has not been confirmed.
When females have sexual relations (with a female or male), they make a loud, distinct, squeaking and screaming call called a ‘copulation call’. Female bonobos are more likely to make this call when they mate with males.
Apart from the above, most of what we know about bonobo communication comes from captive animals. While captive studies can tell us about the range and possibilities of bonobo behavior, it has limited use in telling us about how these animals act in the wild without artificial conditions. In captivity, bonobos have proven to be intelligent problem-solvers who want to communicate their desires and dislikes to their human handlers and can even be playfully mischievous.
The capabilities of bonobos extend to how they learn to communicate. Some captive individuals have been taught to communicate with humans by using symbols on keyboards. These language studies included two-way communication between bonobos and humans, with humans using spoken language to which the bonobos would respond via those symbols. These even include the exchange of complex abstract ideas such as something being “good,” “bad,” or a “surprise!” Famously, a captive bonobo named Kanzi learned 3,000 words and 348 symbols including the words “yogurt,” “chase,” and “tickle.” There is debate among researchers about whether these examples of bonobo communication indicate that bonobos can develop the intricacies of language. However, these experiments demonstrate bonobos’ sophisticated learning capacity and use of language.
Bonobos are polygynous, meaning that one male will mate with multiple females. Females become sexually mature between 6–13 years of age and usually have their first baby at the age of 13 or 14. Mature females develop swellings in their genital area, which attract interest from males, but these swellings may not signal reproductive readiness. The swellings can be false signals that do not indicate when a female is most fertile. As a result, males cannot use them to determine their chances of fathering offspring. Instead, the female can use the swellings to attract multiple males and select which one she wants to mate with, or she can choose not to mate at all.
Bonobo gestation (the amount of time she is pregnant) lasts about 8 months, and females give birth to a single offspring. The baby is dependent on its mother’s milk for more than a year, or until the next offspring is born. As a result, mothers spend almost all their time protecting their young, which leads to very low infant mortality rates. Baby bonobos cling to their mothers’ chests for at least three months and slowly start to leave the safety of their mother’s body as they explore more of their environment. At 6 months, they may move as far as 3 feet (1 m) away. By the time they are one, young bonobos will confidently walk alongside their party on all fours (quadrupedally) like the adults.
As young bonobos leave their mother’s side, they play and interact with other community members. Most adults encourage playtime and are patient with the young apes. At around 2–5 years of age, bonobos are considered juveniles. Juveniles are strong enough to catch up with their fast-moving party but occasionally will climb on their mother’s back to be carried.
Puberty occurs at around the age of 9. Once a female reaches sexual maturity, she leaves the party she was born into (her natal community). She develops bonds with other females who have left their natal group. These bonds usually develop one at a time until a functioning party is formed that can forage together and defend each other from predators and male aggression. These parties consist of mostly unrelated females and the oldest female is usually the highest-ranking individual.
In contrast to females, males tend to stay in the same party or community they were born into (a phenomenon called philopatry).
Bonobos depend on their strong social network between party members for survival. Young bonobos spend a lot of time around adults, observing and learning what to eat, how to avoid predators, and even how to use tools. Sometimes, males who have not left their natal party help take care of or babysit their young cousins.
Bonobos are one of the larger mammals in their region of the Congo. As a result, they are responsible for consuming a lot of food and cycling this nutrition back into the forest soil. As omnivores that travel long distances, bonobos consume leaves, insects, and fruits in one area of the forest and defecate in another part of the forest. This transfers nutrients and seeds across distances that plants would not be able to otherwise accomplish. Therefore, bonobos are major seed dispersers. They help regenerate fruiting trees and maintain plant biodiversity throughout their forest. In the lifespan of a single bonobo, they could disperse as many as 12 million seeds!
Due to their ability to consume a variety of food sources and adapt to their surroundings, they can play multiple ecological roles. They help to control the population of insects and parasites, and they drop fruit on the forest floor, which provides nutritious food for smaller mammals.
It is important to note that leopards and crocodiles are potential predators of bonobos, meaning that bonobos are an essential part of the forest food chain.
The International Union for Conservation of Nature lists the bonobo as Endangered (IUCN, 2016), appearing on the IUCN Red List of Threatened Species.
The challenges of their remote locations and political conflicts make estimating bonobo populations difficult. The Bonobo Conservation Initiative estimates that there are only about 15,000 bonobos left in the wild. Some estimate that numbers are so low that there may be one bonobo per 4 square miles (0.4 per square km)!
Poaching and illegal hunting are their most serious threats. The Congo region has experienced hardships in terms of warfare and political instability and, as a result, the people have experienced poverty and food insecurity. Hunting wildlife for bushmeat is one way people have managed to sustain themselves through these circumstances.
A study found that 270 bonobos were killed in the Congo in 2008. Poachers typically kill the largest bonobos they find, which results in orphaned youngsters and disrupted families. This break-up of bonobo society has negative consequences for the survival of the remaining bonobos in the group, which can have an impact on bonobo behavior and survival for generations to come.
Habitat loss is the next largest threat to the survival of bonobos. During civil unrest, forests were cut down for roads and mining resources for the war effort. The dense swamps and forests also ended up being refuges for people escaping conflicts. Some of these areas became sites for guerilla warfare (smaller fighting groups that were armed and violent). The destruction of natural forests, and human encroachment into these areas, reduced the habitat available for bonobos.
Natural areas are also becoming unusable as mining and agriculture reduce the diversity of plants and habitats available for bonobos. Many forests around the world are being transformed into oil palm plantations because they are quick and cheap to harvest for the growing oil needs in processed foods. About 99% of bonobo habitat is considered suitable for oil palms and forests are already transformed into acres of this monoculture (one type of plant) which damages the geology, environment, and wildlife of the region.
With human developments being so close to the forests, the opportunities for disease transmission between humans and their close genetic relatives are high. Diseases like the Ebola virus can pass from humans to bonobos and threaten entire bonobo communities, especially as bonobos exist in close-knit communities themselves. It’s unlikely bonobos have natural immunity to diseases like Ebola, and an outbreak can wipe out entire populations.
The bonobo is listed in Appendix I of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
Bonobos are fully protected against trade nationally and internationally. Unfortunately, anti-poaching resources aren’t enforced locally and conservation isn’t a national priority. Wars and changing governments in that region have made the situation worse. In the DR Congo, national parks such as the Lomako-Yokokala Faunal Reserve are protected by the military, which has reduced the rampant poaching in the area.
There is also increasing awareness of habitat destruction and the long-lasting negative impact of large monoculture plantations on a nation’s natural resources. As per local traditions of the Congo, the bonobo is considered sacred. Some organizations are trying to appeal to these ideologies to get local support for conservation efforts. The hope is that this awareness seeps through the policies and practices so that the country can balance its economic growth needs with the environment’s ability to sustain its people.
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Written by Acima Cherian, September 2023