In the wild, chimpanzees are more motivated to cooperate than bonobos

JUNE 24, 2020

by Max Planck Society

We humans have unique cooperative systems allowing us to cooperate in large numbers. Furthermore, we provide help to others, even outside the family unit. How we developed these cooperative abilities and helping behavior during our evolutionary past remains highly debated. According to one prominent theory, the interdependence hypothesis, the cognitive skills underlying unique human cooperative abilities evolved when several individuals needed to coordinate their actions to achieve a common goal, for example when hunting large prey or during conflict with other groups. This hypothesis also predicts that humans who rely more on each other to achieve such goals, will be more likely to provide help and support to one another in other situations.

"While we cannot study the behavior of our human ancestors," explains Roman Wittig, a senior author and head of the Taï Chimpanzee Project, "we can learn how relying on others may influence helping behavior in our ancestors by studying our closest living relatives, chimpanzees and bonobos." Chimpanzees are more territorial than bonobos and in some populations engage more frequently in group hunts. According to the interdependence hypothesis, chimpanzees should thus have evolved a higher tendency to cooperate and help others in the group.

To test this hypothesis, researchers from the Max Planck Institute for Evolutionary Anthropology, Harvard University and Liverpool John Moores University, presented 82 chimpanzees and bonobos from five different communities with a model of a Gaboon viper, a deadly snake. During the experiment the apes could cooperate with each other by producing alarm calls to inform conspecifics about the snake. This represents the first experimental study ever conducted in wild bonobos. "This experimental study is a novel and promising approach to probe bonobo's mind," says Gottfried Hohmann, a senior author on the study and head of the LuiKotale bonobo project. Martin Surbeck, co-author on the paper adds: "This study should stimulate several more experimental studies on wild bonobo cooperation, cognition, and communication."

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Bonobo moms play an active role in helping their sons find a mate

MAY 20, 2019

by Cell Press

Many social animals share child-rearing duties, but research publishing May 20 in the journal Current Biology finds that bonobo moms go the extra step and actually take action to ensure their sons will become fathers. From physically preventing other males from mating to bringing their sons in close proximity to ovulating females, bonobo moms bring new meaning to the notion of being overbearing—but in so doing, they increase their sons' chance of fatherhood three-fold.

"This is the first time that we can show the impact of the mother's presence on a very important male fitness trait, which is their fertility," says Martin Surbeck, a primatologist at the Max Planck Institute for Evolutionary Anthropology. "We were surprised to see that the mothers have such a strong, direct influence on the number of grandchildren they get."

Surbeck and his colleagues observed wild populations of bonobos in the Democratic Republic of Congo, as well as wild populations of chimpanzees in Côte d'Ivoire, Tanzania, and Uganda. They found that while both bonobo and chimpanzee mothers would advocate for their sons in male-on-male conflicts, bonobo moms went the extra mile to aid their sons' copulation efforts. This involved protecting their sons' mating attempts from other males, intervening in other male's mating attempts, and intentionally bringing their sons around fertile females.

The bonobo mothers were also able to 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 status—and therefore, better mating opportunities. The authors note that these interactions were rare in chimpanzee societies likely because males hold dominant positions over females, making the actions of chimp mothers less influential than those of bonobo mothers.

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Apes remember their old friends' voices

March 30, 2016

Humanity's closest living relative, the bonobo ape, can remember the voices of old friends for several years, just as people can, researchers have shown.

An international research team from the Universities of St Andrews and Saint-Etienne in France, made the discovery after recording the calls of individual bonobos and playing them to those they had known years before. 

When it was a familiar voice in the recording, the bonobos became excited and would search for the individual, while the animals gave little reaction to hearing the calls of bonobos they had never known.

The team concluded that the primates are therefore capable of remembering the voice of a former group member, even after five years of separation. 

Sumir Keenan, of the School of Psychology and Neuroscience at the University of St Andrews, said: "Members of a bonobo community separate regularly into small groups for hours or even days and often use loud calls to communicate with one another. Moreover, 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.

 "It is fascinating to discover that this knowledge of familiar voices in the long term is another characteristic we share with our closest relatives."

The researchers were able to use recordings of bonobos from zoos across Europe, taking advantage of the fact that some bonobos had experienced several zoos and had formed links past and present with members of their species in different places. 

Mimicking the events characteristic of the arrival of a new bonobo – the scientists played the recorded bonobo calls using carefully hidden speakers. 

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Can a bonobo keep the beat?

Date: November 24, 2015

Source: American Psychological Association

Humans have a remarkable ability to synchronize to complex, temporally structured acoustic signals, an ability which is believed to underlie social coordination and may be a precursor to speech. This ability takes years to develop. Although infants move to periodic rhythmic stimuli, children do not synchronize movements to frequency or tempo until the age of 8 or 9. Synchrony in young children is facilitated by social interaction, and promotes prosocial behavior in both children and adults. Rhythmic behavior has recently been observed in other animals, including parrots, budgerigars, sea lions, rhesus monkeys, and chimpanzees, although in the majority of these cases animals were explicitly trained to synchronize.

Because chimpanzees and bonobos are genetically similar to humans, understanding rhythmic abilities in these species has direct implications for understanding the evolution of speech and music. Indeed, chimpanzees and bonobos display bouts of rhythmic drumming as part of display or play behavior. In a recent paper published in the Journal of Comparative Psychology, Large and Gray (2015) assessed spontaneous and synchronized drumming tempo in a female bonobo (Kuni) who self-selected to participate by regularly approaching a human drummer in a designated research area within a bonobo zoo enclosure. Prior to the experiment, the bonobos (including Kuni) were exposed to a human drummer and were rewarded for any strike of the drum, but were not trained to produce a specific rhythm or to synchronize with the experimenter.

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Human activity and forest loss threatens endangered ape

November 2013: Poaching, forest fragmentation and a growing population are all taking their toll on the endangered bonobo formerly known as the pygmy chimpanzee) and just 28 percent of its range remains suitable for them say scientists.

Using data from nest counts and remote sensing imagery the research team, which included scientists fromUniversity of Georgia, University of Maryland, the Wildlife Conservation Society, found that the bonobo avoids areas of high human activity and forest fragmentation. 

“This assessment is a major step towards addressing the substantial information gap regarding the conservation status of bonobos across their entire range,” said lead author Dr. Jena R. Hickey of Cornell University and the University of Georgia. “The results of the study demonstrate that human activities reduce the amount of effective bonobo habitat and will help us identify where to propose future protected areas for this great ape.” 

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How Similar Are the Gestures of Apes and Human Infants? More Than You Might Suspect

June 6, 2013 — Psychologists who analyzed video footage of a female chimpanzee, a female bonobo and a female human infant in a study to compare different types of gestures at comparable stages of communicative development found remarkable similarities among the three species.

This is the first time such data have been used to compare the development of gestures across species. The chimpanzee and bonobo, formerly called the "pygmy chimpanzee," are the two species most closely related to humans in the evolutionary tree.

"The similarity in the form and function of the gestures in a human infant, a baby chimpanzee and a baby bonobo was remarkable," said Patricia Greenfield, a Distinguished Professor of Psychology at UCLA and co-author of the study, published in the open-access journal Frontiers in Psychology.

Gestures made by all three species included reaching, pointing with fingers or the head, and raising the arms to ask to be picked up. The researchers called "striking" the finding that the gestures of all three species were "predominantly communicative," Greenfield said.

To be classified as communicative, a gesture had to include eye contact with the conversational partner, be accompanied by vocalization (non-speech sounds) or include a visible behavioral effort to elicit a response. The same standard was used for all three species. For all three, gestures were usually accompanied by one or more behavioral signs of an intention to communicate.

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