In the summer of 2019, Planckendael ZOO opened a new bonobo enclosure. The new building was designed and built according to the latest insights into the make-up of bonobo groups and their behaviour. Scientists at Antwerp ZOO and Planckendael ZOO use this to conduct more research. Now, after thirty years of fundamental work, mostly observation, they can carry out more experimental research with the bonobos, prompting them to perform tests or play games, for example. Two ongoing research projects aim to fathom out the concept of cooperation between bonobos and how emotions can influence the animals' decisions. “This will enable us to learn more about how bonobos think, how they live together in groups, how they learn, how they remember. That information will in turn enable us to improve our understanding of bonobos and their affinity with similar species such as chimpanzees and humans", explains Zjef Pereboom, Manager Research & Conservation at Antwerp ZOO and Planckendael ZOO.

BACKGROUND

In the wild, this endangered species is only found in Congo, south of the Congo River, where as few as 15,000 to 50,000 bonobos remain today. Hunting, poaching, the loss and fragmentation of their habitat as well as outbreaks of diseases endanger these African anthropoids further still. Planckendael ZOO plays a key role in the bonobo breeding programme. Firstly because it has been doing so for a very long time already but also because, for over 30 years, Planckendael ZOO has been conducting scientific research on bonobos living in zoos. "We examine social behaviour, primarily to learn more about the make-up of bonobo groups. Based on our findings, we then seek to advise zoos on how best to keep and manage their bonobo populations. This enables us to maintain the animals’ well-being at optimal levels", Pereboom explains. "At the same time, we would also like simply to understand bonobos better.”

We combine our findings at Planckendael ZOO with the results of studies of bonobos living in the wild in Congo. We know, for example, that the moment young females mature they leave the group to avoid incest. So we copy this principle in the management of our bonobo populations in zoos. "The moment a female shows signs of becoming reproductive, we decide to move her to a different group, away from her father or brothers."

An important part of our research focuses more on fundamental scientific questions, with the scientists seeking to gain a better understanding of bonobos as a species, from an evolutionary perspective. “As bonobos are the species most closely related to humans, along with chimpanzees, these studies can teach us an awful lot about ourselves, as humans, and about our own evolutionary history", Pereboom continues. That research is not restricted to Planckendael ZOO. Since 2013, our team of scientists has again been working at LuiKotale field site in DR Congo, close to the south-western boundary of Salonga National Park. The research there focuses primarily on the socioecology of bonobos living in the wild, observing how they behave in an ecological setting. One aspect these studies examine is how bonobos make use of, and the role they play in the rainforests. We also observe their social networks, their sexual behaviour, aggression and reconciliation, nest-building, the use of tools, and their feeding patterns.

The research at Planckendael ZOO applies a predominantly experimental approach, aimed at learning more about the underlying social and cognitive processes in bonobos. More precisely, we seek to identify and interpret social relationships among bonobos. How do competition and cooperation work, do bonobos display any sense of equity/inequity, unselfishness (or fair sharing), how do they make certain choices and what part do personality and emotions play in that?

HOW DOES THE RESEARCH WORK IN PRACTICE?

Jonas Verspeek, doctoral student at the University of Antwerp, Antwerp ZOO & Planckendael ZOO, is trying to fathom out how bonobos cooperate. He prompts the animals to perform various tests and observes how they respond. "One of the tests I do aims to see whether they have any sense of inequity. Earlier research I conducted at Planckendael ZOO revealed that bonobos clearly prefer the taste of grapes to that of parsnip. During the test to examine their sense of fairness, the bonobos have to return a plastic stick I give them. I reward one of them with something they like, such as a grape, and the other with something less tasty, a piece of parsnip. During this study I have already noticed that some bonobos who are given the less tasty reward for the same task give the parsnip back. A possible explanation for them rejecting the reward is that they expect the same reward for the same task. This could indicate some kind of sense of equity." Verspeek also tests whether bonobos are prepared to give something to another without there being any direct benefit to them. He hopes that combining the two tests will provide more insight into how bonobos cooperate with each other.

"Some bonobos want the same reward for the same task. In other words they would seem to have some sense of equity."

Daan Laméris, who is also doctoral student at the University of Antwerp, Antwerp ZOO & Planckendael ZOO, is researching emotions in bonobos. “Emotions are very subjective and it is very easy for us, as humans, to explain how we feel. We obviously can't just ask animals so I am doing tests to try to find out. From the literature on humans we know that our emotions influence the focus of our attention, what we remember and how we make our decisions. We can apply the same principle to bonobos, but the other way round. How the variations in their memory, in their attention, can be traced back to the emotions they were feeling at the time. Laméris introduces a touch screen and trains the bonobos with tests used in human psychology. "One example is a kind of memory game, where they are shown a photo of another bonobo expressing either positive or negative emotions. After a delay of 20 or 30 seconds they are shown the same photo again, together with another photo., and the aim is for them to click the same photo. In humans, we know that people are more likely to remember photos that reflect the emotions they are then feeling and we rather expect bonobos to do the same. So if the bonobos remember photos of positive emotions better than ones of negative emotions, we could deduce that they are feeling good." Laméris also uses a reward system to train the animals. "We start by displaying a very large spot. Out of sheer curiosity, they will press the spot and then automatically be rewarded with a treat. That treat should motivate them. They will get to enjoy the game and I can gradually expand it step by step to include the tests I want to carry out with the photos.

"In humans, we know that people are more likely to remember photos which reflect the emotions they are then feeling and we rather expect bonobos to do the same."

Both Verspeek and Laméris work non-invasively and limit the amount of actual interaction with the animals. Observation is key.

WHAT IMPACT WILL THE RESEARCH HAVE?

As researchers, we can try to compare cooperation among bonobos with the kind of cooperation we see among humans, where we observe that cooperation between people works extremely well in a whole range of situations, such as building new towns and cities for example. Combining the tests relating to inequity with the study into prosocial behaviour, a willingness to give something to someone else, enables me to assess whether they cooperate effectively in situations in which cooperation is essential. In some situations you have to be able to accept that another gets more than you and on other occasions you have to be willing to give someone something without gaining anything from that yourself."

As bonobos are so closely related to humans, from an evolutionary perspective, Laméris hopes that his study will reveal more about how human emotions evolved. "At the same time, we hope that these tests will also improve our understanding of bonobos' likes and dislikes and ultimately to apply this knowledge to improve their well-being."