Bonobos

Bonobos were formerly known as pygmy chimps, but are now recognized as their own, separate species. However, you still frequently hear them referred to as a kind of subspecies of chimpanzee, which they are not. They were first recognized by anatomists as a separate species in 1929; but first suggested they were a separate species by Protielje, a Dutch naturalist and Robert Yerkes, the pioneering ape researcher about 1916 or so. They are as closely related to us as to the chimp, and in many ways, are much closer behaviorally to humans than are the chimpanzees, the close primate ancestor on which human ancestral behavior has been modeled. Based on the assumptions of evolutionary psychology, we can learn something about ourselves from watching bonobos, because our species share an ancestor who is believed to have existed about 6 million years ago. (show overhead of divergence).

As Frans de Waal, one of the foremost researchers of captive bonobo behavior has said, ÒIn everything they do they resemble us. A complaining youngster pouts his lips like an unhappy child or stretches out an open hand to beg for food. In the midst of sexual intercourse, a female may squeal with apparent pleasure. And at play, bonobos utter coarse laughs when their partners tickle their bellies or armpits. There is no escape, we are looking at an animal so akin to ourselves that the dividing line is seriously blurred.Ó

He suggests that had we known about bonobos before chimps, reconstructions of human evolution might have emphasized sexual relations, equality between males and females and the origin of the family, instead of war, hunting and tool technology. In many ways, chimps are a good model of human ancestral behavior in that they show cooperative hunting, food-sharing, tool use, power politics and primitive warfare, as well as the capability of learning symbolic communication such as sign language. For all of these reasons (plus lack of any real knowledge of bonobo behavior till the 1970s), scientists chose to model our ancestral behavior on chimpanzee behavior. However, because of this, what has also persisted is the belief that male dominance is the natural state of affairs in humans, since in chimpanzee society, males, even young males, are always dominant to females. Bonobo society, in contrast, is a female-centered society, that is egalitarian, and substitutes sex for aggression. Females are co-dominant with males and when males attempt to coerce them, they ignore the males. It is impossible to understand the social life of this species without attention to its sexual behavior, the two are inseparable. Whereas in most other species, sexual behavior is a fairly distinct behavioral category that may occur only rarely, in the Bonobo, it has become an integral part of social relationships and not just between males and females. Bonobos engage in sex in every combination possible: male-male; male female; female -female; male-juvenile; female-juvenile and so on. The frequency of sexual contact is higher than among other primates, but itÕs rate of reproduction is about the same as that of the chimpanzee, with females giving birth about every 5 years in the wild. This combination of low reproduction and high sexual appetite not linked to reproduction is very similar to that of humans. de Waal has suggested that the Bonobo may help us see human sexual relationships in a broader context, with certain aspects of human sexuality such as pleasure, love and bonding being emphasized more than formerly, and that these aspects of sexuality have probably characterized our species from very early on. (primatologists have started using the word Bonobo as a verb, as in ÒWeÕre going to bonobo tonight!Ó).

It has been suggested that Bonobos most closely resemble our common ancestor of 6 million years ago. The body proportions of the Bonobo are such that the upper body is light compared to the lower body (an adaptation related to bipedalism) and they have elongated legs (compared to other non-human primates). They are able to walk upright and do so often, using their hands to carry objects, and when standing upright, they show a very human posture. In addition, Bonobos are the only other primate besides humans in which the orientation of the femaleÕs genitals is towards the front of the body, allowing face to face copulation.

Habitat: Bonobos are the least studied and the least understood of all the great apes. Their habitat is extremely remote, the political situation in Central Africa can be highly unstable, and they are quite shy and require a great deal of habituation to humans before they can be approached and watched. They are found in Zaire (name may have come from a misspelling of Bolobo, a Zaire town; formerly known as Belgian Congo) a large country about the size of the US east of the Mississippi. It has only around 40 million people, 40% of whom live in large, urban areas. Nearly 80% of Zaire is covered by forest. Show map on page 58 and location of Lomako and Wamba. This area where the Bonobos live is one of the most sparsely populated and least developed of the tropics, and is part of the second largest solid stretch of rain forest in the world. This area is bounded to the north and west by the Zaire River, to the east by the Lomami River and to the south by the Kasai and Sankuru river. Bonobos may only inhabit about 1/4 of this region and their distribution is very patchy. Early figures estimated the population to be about 100,000 animals, at present a more realistic number is probably 10,000 Ð 25,000. Bonobos are currently classified as vulnerable to extinction by the International Union for Conservation of Nature and as endangered by the U.S. Fish and Wildlfie Service. They are protected from hunting, killing , trapping and trade by the Convention on International Trade in endangered Species. In addition to all the locations known where they exist in the wild in Zaire, they are also present on one forest reserve in Zaire, called Salonga National Park. Unfortunately, this park is under the control (at least when this book was written; 1997) by heavily armed poacher gangs who prey on elephants and hippos. It is unknown what their impact is on the reserve Bonobos, who are not present in high numbers.

Wamba Forest is part of a larger protection area, the Luo Scientific Reserve, which includes 1000 resident humans who co-exist with the Bonobos. There used to be a taboo against eating bonbobs based on ancient beliefs that Bonobos are our kin, almost like ancestors. This taboo was respected till 1984, when the first poaching incident at Wamba occurred when investigators were absent, and a poacher killed a young adult male and sold the carcass for meat in a local village. The second case, in 1987 was more serious. Again during the absence of the investigators, soldiers were ordered to capture apes and they beat trackers who refused to cooperate. There was a mass hunt, and several adult males and two nursing mothers were killed and their infants collected. Kano's chief tracker placed himself between the apes and the soldiers and prevented the killing of more. During the 8 years between 1976 Ð 1983, only 3 individuals were lost, but during the same duration of time from 1984 Ð 1991, 11 disappeared. From 1995 Ð 1997, 10 more disappeared. Almost all disappearances have occurred when investigators are absent and the group size of Wamba, which was growing, is now declining. It is clear that the taboo against hunting Bonobos has declined and this is at least partly because of the civil wars which have raged in Zaire and which have destroyed the local economy and cultivated food sources so that people who live in or by the forest are now relying much more heavily on wild game than previously and are also selling wild animal meat, since this is one of the few ways they have to make money. In addition, although guns are rare, local hunters set wire snares to trap many different kinds of animals, and Bonobos are caught and severely injured in such traps.

Wamba; Takoyoshi Kano is the field researcher who studies Bonobos at Wamba. He is a Japanese researcher (many of the most famous primate researchers are Japanese, partly because of behavioral studies done on JapanÕs native macaques). The perspective of researchers from the University of Kyoto, is different from that of Western science, which focuses on the Darwinian struggle for life and reproduction. Instead, Japanese primatology emphasizes social relationships and the social structure of a species. Long-term records and recognition of hundreds of individuals as well as provisioning of wild populations to attract the animals are staples of their research. One of the founders of this school of thought, advocates identification with animal subjects and argues that a certain level of subjectivity is necessary for a full understanding of non-human behavior. Kano was the first scientist to successfully observe Bonobos in the wild, and this was mainly because he planted sugar cane in a clearing in the forest to attract them. Eastern thought has now been accepted by and integrated into Western primatology studies, so that such activities as recognizing individuals, following animals for their entire lifespan, and feeling empathy for the animals and suggesting that non-humans have culture is now considered to be desirable.

Both chimps and Bonobos live in what are called fission-fusion societies, in which groups, called parties, are constantly breaking up and reforming again. All associations, except the one between mother and infant are temporary. In chimpanzees, they form large unit-groups, or communities; all members of a particular community mix freely in ever-changing parties, but members of different communities never mingle (except when young females migrate in). Both species are also male-philopatric; with males staying in their natal groups and females dispersing to neighboring groups. Thus, in any chimp or Bonobo group, all the males of a party will have known each other from birth and are often related to one another and there are close bonds between maternal brothers. Bonobo females appear to be more affiliative than female chimpanzees, at least than those chimps in East Africa who tend to travel mostly on their own with their infant offspring. The major difference between the two species seems to be that female-female bonding is more important in Bonobos, and male-male bonding is more important in chimpanzees, but there is great flexibility within each species. The one consistent difference is a closer relationship between the sexes in Bonobos. At Wamba, 3/4 of the traveling parties are mixed and include adults of both sexes and mothers with offspring. Grooming occurs most commonly between sexes. In the chimpanzee, males will travel with a sexually receptive female, but since females are only occasionally in this state, the sexes rarely accompany each other. Male chimps are also sometimes very aggressive against adult females and infants, and for this reason, females with infants tend to travel on their own or sometimes with other females and join parties of chimps only occasionally and for short periods of time since their infants, and sometimes they themselves can be at risk from the males. In Bonobos, parties are made up of all combinations of females, males and infants and it is common for mother-son dyads to persist long after adolescence, with even fully grown and mature males accompanying their mothers through the forest. Since females migrate out, the dominant relationship in Bonobo society is that of mother-son, and the role of the mother is so important in Bonobo society that Kano has called mothers the ÒcoreÓ of Bonobo socieity. Bonobos also form larger parties than chimps (often about 20), which is several times larger than the typical chimp party.

Community size is similar however, with communities ranging from 25 Ð 75, but some up to 120. Unlike chimps, the entire community forms at night and they build nests in the tree-tops and sleep in close proximity to each other. Bonobos, unlike chimps, visit between communities, and while there may be some hostility and tension, injury and death does not result as it would with the highly aggressive chimpanzee. Visiting is characterized by grooming and sex between adult females, playing among the young, sex between adult males and females, and overt hostility (screaming, chasing, barking) between males, but no actual fighting.

Dominance: Bonobos, unlike many other species, lack formalized rituals of dominance and submission, and this is particularly true of adult females. Status is not wholly absent, but is so vague that Kano does not speak of Ôhigh-rankingÕ females, but only of ÔinfluentialÕ females. He claims that females are respected out of affection, not because their rank is high. Aggression does occur between females, one may jump on another and bite her and steal her sugar cane, yet they constitute such a minuscule proportion of aggressive disputes that for all intents and purposes, females can be said to be remarkably tolerant of one another. If there is a female rank order, it is based on seniority, rather than physical intimidation, with older females having higher status than younger. Those with lowest status are those females who have recently immigrated into the group and who have not yet produced offspring. These females usually single out one, older, higher status female and attempt through grooming and sexual contact to make her their special friend, which helps them to be accepted by the group.

Among males, there is more of a dominance hierarchy, with more fighting among males than females. Rank position near the top, especially the alpha male, is quite apparent, but mid-ranking and lower positions are not so obvious to researchers. Rank order is mostly expressed by the direction of aggressive chases (the chaser is dominant), and these encounters rarely escalate and are quickly solved by conciliatory contact in which the males mount each other or rub their scrotums together while standing back to back. In dominance fights that have been observed where male rank is changing, in both fights, mothers were the deciding factor in who won. In one fight, the mother of the challenger was young and strong and helped fight and chase the alpha male. In the second case, the mother of the alpha male was quite old and weak, and when the beta animal (whose mother was the beta female) attacked the alpha male, he got no help from his mother. He not only lost his alpha status, but his mother lost hers too, since she was also physically attacked and beaten by the beta female. In both cases, bites were not exchanged, but blows and slaps were.

This also illustrates one of the most puzzling aspects of Bonobo society, in which females dominate males. We know of only two other exceptions to the rule that males dominate females in mammals, and those are the spotted hyena and the Madagascar lemur. In most mammalian species, males are larger and possess greater weaponry and this is presumed to be the basis of male dominance. In Bonobos, however, both in the wild and in captivity, females are dominant over access to food, will band together and chase off males who try to harass a female. In traveling parties, females form the safe central portion of the party, surrounded by their sons and the outside group is made up of unrelated, unattached males. Females also do not share food with males, and all females are dominant to males when it comes to gaining access to food. Even if a male found the food first, the female will claim it and while she may share with her offspring, she shares with no one else. Males are often reduced to begging for or stealing food from infants on the periphery of the group of feeding females. In addition, it is clear that females determine the ranks of their sons and will actively fight to obtain a higher rank for them. Finally, males NEVER attack females, although females will attack males.

The Bonobo is also a puzzle in that in other species in which one sex migrates, same sex animals stay in the natal unit bond. Thus we see mother-daughter bonding in spotted hyenas (where sons migrate) and father-son bonding in chimpanzees (where daughters migrate). In contrast, Bonobos, while females migrate, they bond to unrelated females in their new group, while males in the natal group appear not to bond. It has been suggested that this female bonding (which has been characterized either as bonding or as behaviors to reduce tension with no real bonding Ð controversy over which one it is) can occur in Bonobos because their food sources are so abundant that females do not need to compete over food and so can form large social groups. In contrast, chimp food is much more dispersed and there is much more competition between females for access to food (partly because chimps and gorillas are sympatric and Bonobos and gorillas are not).

Food: Wamba investigators have followed Bonobos into the forest, of which there are 3 kinds. Swamp forest near the rivers includes relatively low trees, supported by prop roots and leaning against one another in the mud. Primary forest grows on firm land and has a dense, overlapping tree crown and much taller trees with little light on the forest floor and little underbrush. Finally, there are clear-cut areas which have been deforested and then grown back, although the density of the trees is still less than in primary forest (and where thick patches of herbs grown due to sunlight reaching the forest floor). Bonobos use all 3 habitats, but prefer primary forest, because more food can be found there more easily. They primarily eat fruits and pith from plants, as well as leaves and shoots of herbs. These foods have a high protein content, so unlike chimps, Bonobos are less dependent on animal protein. Chimps catch and kill monkeys for food, while Bonobos catch monkeys and appear to play with them (sometimes to the monkeys extreme detriment) but have not been observed eating monkeys, even after they have accidentally killed them while playing. Bonobos do eat insects, earthworms and eggs. They also capture reptiles, shrews, flying squirrels, small forest antelopes and perhaps fish and shrimp. However, on the basis of fecal analysis at Wamba, it appears that non-plant foods make up only about 1% of their diet.

Sexual behavior: de Waal suggests that much of the sexual behavior seen in Bonobos should not be called ÔsexÕ since humans tend to think of sex as a behavioral category aimed at achieving orgasm. We associate sex with reproduction and sexual pleasure, whereas in the Bonobo, it mixes with all kinds of other tendencies, with orgasm and reproduction only one of its many functions. On the other hand, de Waal feels that human sexuality, too, may have a broader significance than commonly admitted, and that moral constraints may have made it difficult or impossible for us to realize or admit how much sex permeates all aspects of social life. F. de Waal suggests that studying Bonobo sex may provide insight into how our sexuality might function without moral constraints that are in place (many of which exist for a good reason).

Face to face mating used to be seen by humans as a proof of the dignity and sensibility separating civilized humans from animals. However, few sexual patterns typical of humans are absent in Bonobos. Female genital tissue, mainly labia and clitoris, periodically swell up indicating sexual receptivity. The swelling and vulva are located more between the legs than in a chimpanzee and the clitoris is prominent, erectile and frontally oriented. Given this positioning, it is not surprising that females prefer the frontal position for sex, since it provides optimal stimulation. Females invariably invite males by lying on their backs, and will sometimes switch to this position if the couple started out in another position. However, ventral-dorsal positions occur twice as often as ventral-ventral. Another characteristic position is female-female ventral-ventral, in which one female is carried by another and both females can make sideways movements and rub their clitorises together. It has been observed in all Bonobo groups known and is unique to the species (usually known in the trade as G-G rubbing, for genital-genital rubbing). Both females and males also engage in rump-rump contact, in which animals face in opposite directions and rub genitals. In males, the males back up to each other and rub rumps and scrota together. In females, one lies on her back and the other stands over her with her back turned and they rub genitals. Males also engage in mutual penis rubbing, with one male, usually the younger, on his back and the other male thrusting. Both males have erections and their erections rub together. Kano reports that he has never seen ejaculations during this sexual behavior, nor has he seen anal penetration between males. Kano also reports seeing penis fencing, a rare behavior, in which two males hang from branches face to face while rubbing their penises together. Adults also engage in mouth to mouth kissing, with extensive tongue contact; fellatio in which one partner takes the penis of the other into the mouth and stimulates it (happens a lot during rough and tumble play among juveniles); and manual massage of otherÕs genitals, usually by an adult male to a juvenile male. The young male presents his erect penis to the older male who closes his palm loosely around it and makes up and down movements. All animals also engage in masturbation, with young male juveniles and adult females being the most frequent masturbators. Again, neither genital massage or masturbation has been observed to lead to orgasim. Infants closely watch and try to participate in such activities and sometimes present themselves to adults for sex. In this case, the older animal may provide some gentle stimulation, such as touching genitals or a male may simulate thrusting, but actual sex with infants does not occur.

de Waal refutes Roger Short's contention that human males have the longest penis of any mammal (per body size). He says that while the Bonobo penis has a smaller circumference than that of humans, it is certainly longer (and they have a smaller body size).

Perhaps most interesting is the fact that sexual behavior in this species changes as a result of partner feedback. Slow motion studies of copulatory behavior has shown that the speed or intensity of male thrusting is altered or even terminated by the facial expression and vocalizations of the partner. On numerous occasions, either the male or female was observed to terminate thrusting when the partner could not be engaged in eye contact or otherwise indicated disinterest by yawning or self-grooming.

de Waal hastens to add that sexual activity in Bonobos is strikingly casual and relaxed and seems a natural part of their social life. Much of the sexual behavior is not carried through to orgasim, and the average copulation is short, about 13 seconds. He says Bonobo life is a social life peppered by brief moments of sexual activity, and that this sex serves the purpose of defusing possible competitive social situations, such as competition over food, or over fights over rank, or because of defense of young against other adults. Bonobos substitute sex for rivalries, to reduce competition, to induce sharing of food and to facilitate peace making in the wake of aggression. In de WaalÕs studies, sex occurs as often when there is no possibility of reproduction as it did for reproduction and he speculates that sex with no possibility of reproduction occurs in about 3/4 of all sexual encounters.

Care of young rests with the female. Males will play with young and protect them, but their investment essentially is nil beyond insemination, since the adults do not form pair bonds. Mothers, on the other hand have an 8-month gestation and nurse for 4 years and carry and protect offspring for even longer. The maternal investment of apes is equaled or surpassed only by a very few species, such as elephants, whales, grizzlies and ourselves. Females give birth about every 4.5 Ð 5 years and mothers can often be seen with an infant clinging to her belly and a juvenile riding on her back.

Bonobos also show an extended sexual receptivity that is more like that of humans than of other primates. Females are most willing to engage in sex when they are maximally swollen Ð but increased receptivity has been achieved by extending the period of genital swelling. The chimpanzee has a menstrual cycle of about 35 days, but the BonoboÕs is closer to 45 days, and the period of swelling covers 75% of it (34/45 days a female Bonobo will copulate) (chimps will copulate through about half of their menstrual cycle). In addition, Bonobo females resume swelling one year after birth, which adds to the amount of time they are sexually attractive to males. Thus, while the chimpanzee female is sexually receptive less than 5% of her adult life, the Bonobo female is receptive almost half the time. Females leave their natal group at about the age of 7 and previous to this, they seem to enter a sexually inactive stage, which may be designed to prevent inbreeding with relatives in the natal group. They generally have their first offspring about the age of 13 or 14, but are sexually receptive once they join a new group, so there is an entended period during which they show sexual swellings are engage in sex but are not fertile.

Infanticide is unknown among the Bonobos and this may be due to their mating system. The highest status males do most of the matings, but since females have sexual swellings even when they are not fertile and they also sneak off to have copulations with lower ranking males, there is no way for any male to determine paternity. In this case, infanticide seems not to have developed since paternity is unknown anyway. In the closely related chimp, although females are polyandrous, they only swell when they are receptive, so a male may actually know which females he might have impregnated and selectively kill only those infants for whom he cannot be the father (although this has not been proven).

de Waal suggests that the defining moment in the social evolution of the Bonobo probably took place when females began to have more frequent and longer-lasting sexual swellings. This reduced competition among males, obscured paternity, and promoted sociosexual relations in all partner combinations, particularly among females. The end result was that females formed a secondary sisterhood, gained the upper hand in society and freed themselves from the curse of infanticide.

Empathy: de Waal suggests that the Bonobo is cognitively specialized to read emotions and to take the point of others. He cites as examples the fact that Bonobos regulate their sexual performance based on what they read in their partner's eyes or faces, that they stimulate each other sexually without being stimulated themselves and that they defuse conflict with sex. He suggests that in looking for evidence of intelligence in tool use (of which Bonobos show none) we are looking in the wrong spot, but instead should be looking for 'social intelligence'. Once evidence of this social intelligence is the 'taboo nest'. Bonobos build nests in trees every night, but also for resting, grooming or playing in during the daytime. These nests represent a 'personal space' that cannot be infringed upon, not even by the nest maker's closest companions, including offspring. For example, youngsters do not enter their mother's nest without being invited, but remain at the edge, requesting access by means of facial expressions and distress calls. If nests represent personal space, then this allows females to wean offspring and force them to nest elsewhere when they have reached the correct age. It also allows the avoidance of conflict, in that individuals can escape to a nest as a refuge. For example, some field researchers have seen Bonobos feeding on favorite foods, who, when they see others approaching to ask for the food, they quickly break off a few branches and construct a rudimentary nest. Since they were sitting in a 'nest', they were left alone and didn't have to share their food. In another case, an adult male escaped the charging display of another male by quickly climbing and tree and making a nest. In response, the charging male stopped at the base of the tree and moved away.

Here is another story about Bonobo empathy: Betty Walsh, an animal caretaker, observed the following incident involving a 7 year old female Bonobo named Kuni at Twycross Zoo in England. One day, Kuni captured a starling. Out of fear that she might hurt the bird, the keeper urged Kuni to let it go. Kuni took the bird and gently set it on its feet, right side up. When it didnÕt move, Kuni tossed it in the air. However, it returned to sitting on the earth, probably because it was too stunned or terrified to fly. Kuni then picked it up, climbed to the highest point on the highest tree, wrapped her legs around the trunk so that she had both hands free and carefully unfolded the bird's wings and spread them wide open on her palm and then threw the bird into the air as hard as she could. Unfortunately, it was still too stunned to make it over the barrier, so it sat on the edge of the moat where Kuni guarded it for a long time from the juveniles until it finally flew away.

Kakowet at the San Diego Zoo, the patriarch of captive N. American Bonobos was sitting by the moat surrounding their enclosure which had been drained for cleaning. After scrubbing the moat and releasing the apes, the keepers went to turn on the valve for refilling the moat when all of a sudden Kakowet started screaming and waving his arms at them. The keepers said it was almost as if he could talk. It turned out that several young Bonobos had entered the moat but were unable to get out. The keepers provided a chain for them to climb and all got out except for the smallest Bonobo, who was rescued by Kakowet.

de Wall relates his own moat story. By the time he got to the San Diego Zoo, the moat was no longer filled with water, since apes cannot swim. Thus the animals were provided with a chain so they could climb in and out of the moat. If the dominant male, Vernon, went into the moat, Kalind, another male would pull up the chain and then look down with an open-mouthed play face and slap the side of the moat. Loretta, the only other adult in the colony, would then rush over and drop the chain back into the moat and guard it until Vernon could climb out. Both Kalind and Loretta seemed to understand the purpose of the chain for someone at the bottom of the moat and to act accordingly; one by teasing and one by helping. The ability to adopt the viewpoint of another is a hotly debated topic in cognitive psychology, it is considered to be an advanced cognitive capability, which has been believed to be unique to our species. Unfortunately, no experiments on the ability to take another individual's viewpoint have been conducted with Bonobos, although they have been with chimps.