Bonding with bonobosTORY

People don’t tend to take bonobos seriously, but there’s a lot we could learn from our gentle, matriarchal cousins.

Meet the friendly but elusive bonobos that reside in one of the most remote regions of the Congo

We have two sets of cousins in Africa. We have many traits in common with both – traits we share with one and not the other, as well as traits that are uniquely our own. You have probably heard about our chimpanzee cousins many times before. They are relatively easy to visit, and there are lots of photos and videos. They often come up in conversation about evolution and how we came to be human.

The other cousins are more of a mystery. They live deep in the Congo Basin, in a luminous wilderness that may be the last of its kind on Earth. These cousins are shy. A long, bloody war in their country made them inaccessible for decades. But the war is over, and it is time to meet these long-lost relatives. Introducing bonobos… at long last.

“To see them for the first time was fascinating,” says Roland Hilgartner, a photographer and primatologist. “When they came down from the trees, I was impressed by their graceful movements, how beautiful they were. Especially looking into their eyes. It’s not hard to see we are so closely related.”

To get to the bonobos you must fly into Kinshasa, the capital of the Democratic Republic of Congo. Then you charter a plane and fly four hours north into the city of Djoulu, then ride for five hours on the back

of a motorbike to the village of Yetee, where you must stay for at least one dinner hosted by the Bondango people, the local guardians of the forest. From there it is another hour on foot to Lonoa, the research camp named after a river that weaves through the forest.

Arriving at Lonoa is like stepping back in time. Dwarfed by ancient trees shooting 30m high, simple huts are woven from what can be found in the forest. Washing is slung over twine to dry. There's no electricity or running water. Just outside camp, bonobos are calling.

“I remember the females were unhappy with one of the males for some reason,” says Dr Martin Surbeck of the Max Planck Institute of Evolutionary Anthropology. Surbeck is the director of the Loana research site, and one of the world’s few bonobo experts. “They were all shouting and screaming at him. Suddenly they turned around and saw me, and decided I was the one causing trouble. All the females started shouting and screaming at me. I was scared. Really scared.”

In general, females have it rough in our primate family. Chimpanzees males can be very aggressive towards a female, especially when she is sexually receptive. Males know when a female is ovulating because the pink part of her bottom swells, advertising exactly when she is most likely to conceive. All the high-ranking males attack her, beating her into submission so she will mate with them.

The female’s only defence is to stay close to the alpha male as protection. Once she has her baby, if the male loses his status, the new alpha may kill her infant. This perpetuates a cycle of violence, where aggressive males have the advantage and infanticide quickly returns nursing mothers to a reproductive state.

Female dominance

Bonobo females will have none of this kind of behaviour. They hide their ovulation with swellings that last for longer, so males cannot tell exactly when they are ovulating. Also, female bonobos can be extremely aggressive towards males who start acting like chimpanzees. Any male who tries to force females into mating is met with fierce opposition – often from a coalition of angry females. And if any male even looks at a baby the wrong way, they quickly feel the full force of female wrath. Females work together so that even though males might win in terms of size, females always win in terms of numbers.

“Female bonobos get away with anything,” says Surbeck. “I’ve seen them pull a male’s legs right out from under him so he trips over and falls. They think this is so funny.” If this sounds unorthodox – it is. There are some animals such as hyenas where females are dominant to males. But female hyenas are bigger than males, with more muscles and more male hormones, such as testosterone. Female hyenas hunt and fight. They even have pseudo-penises. But bonobo females are smaller than males. It is extremely rare for females to dominate males without a physical advantage. Even more unorthodox is how female bonobos are dominant.

In chimpanzees, the males mostly socialise with other males. They take the best spot in the fruiting trees, leaving the females to scramble for fruit lower down. “In bonobos,” Surbeck says, “it is mostly the females who are in the best part of the tree. If a male wants to come in he can – if his mother is there.”

The best chance of a male bonobo getting access to females is through his mother. It is his mother who introduces him to all her friends, and any new female who has arrived. Unlike chimpanzees, bonobo males do not attempt to dominate their mothers. They achieve all their status and rank through her. In fact, there are some bonobo babies who outrank adult males. And even if an adult male is higher ranking than a baby, the male is always very well behaved.

“High ranking chimpanzee males have higher testosterone and cortisol,” says Surbeck. “In bonobo males it is the opposite. The high-ranking males have lower testosterone. They need to stay calm to remain in the centre of the group with the females. They can’t cause any trouble. You wouldn’t want to get kicked out of the tree by Mum.”

You might think that male bonobos might suffer for their unmanliness in terms of reproductive success. Surbeck certainly did. “I thought, you know, there is a lot of mating, everybody gets a little bit of a share, the males don’t fight, so the paternity would be more evenly distributed.” But when Surbeck looked at paternity, it was the opposite. The

The best chance of a male bonobo getting access to females is through his mother introducing them.

Being nice to females, kind to infants and sweet to your mum seems to work very well.

highest-ranking bonobo male – the friendliest and best-behaved – had most of the babies. As a reproductive strategy, being nice to females, kind to infants and sweet to your mum seems to work very well.

In most mammals, it is the males who leave their mother’s group and find a new community. In bonobos and chimpanzees, it is the females who emigrate. For chimpanzee females, this is the moment where they receive the most aggression from other females. The resident females of the new group attack the new female, sometimes killing her baby, if she has one. The female immigrant becomes one of the lowest-ranking chimpanzees in the group. She can only seek protection from the males, who will direct their aggression towards her later, when she is sexually receptive.

In bonobos, an immigrant female is greeted with kindness and excitement. The other females rush towards her, compete to groom and rub genitals with her. These resident females have been seen to defend the new female against males they have known for years. Mothers have even defended new females against their own sons.

This kindness seemed to extend towards all strangers. Our research group played a game with bonobos at the Lola ya Bonobo sanctuary in Congo. Say you have $100. There is someone in the next room, a stranger you have never met before and who you will never see. Then there is someone in the other room, who is a friend. You can either share with your friend, share with the stranger, or keep all the money. Most people usually share with their friend. It makes sense to share with someone who might return the favour later.

Acts of kindness

We played this game with bonobos, using food instead of money. The bonobo in the middle was a bonobo female called Kalina, and we gave her a pile of fruit. She could choose to unlock the door for either her friend or a stranger. Kalina opened the door to share with a stranger. Then once the stranger was in the room, the stranger opened the door for the friend, so all three bonobos could eat together.

When we ran another version of this experiment where Kalina was not even in the room with the food, she still opened the door for the stranger, even though she did not get any food, and could not play with the stranger once the door was opened. We found that bonobos would help a stranger, even when there was absolutely no reward.

In chimpanzees, relationships between strangers are fraught with tension. As a male chimpanzee, you are more likely to be killed by a male stranger than by anyone else. Bonobos have no reason to be afraid of strangers; any scuffle that might occur is minor compared to what is seen in chimpanzees. We found that bonobos are not only non-aggressive towards strangers, they are attracted to them. This attraction allows them to help a stranger in a way we will never observe in chimpanzees.

Only last year, in the wild, bonobo researchers Barbara Fruth and Gotfried Hohmann saw something incredible. One afternoon, bonobos from the Bompusa West community met up with those from Bompusa East. The alpha male of the Bompusa West caught a small antelope. Bonobos from both

communities approached him. He moved into the crown of a tall tree, followed by nine females ( four from one group, five from the other) and their offspring. For the next half an hour, he shared meat with everyone.

When anthropologist Herbert Spencer read Darwin’s On the Origin of Species, he coined the phrase, “survival of the fittest”. But over the years, fitness was confused with physical fitness, such as size and strength. Coupled with the observations of violence in nature, survival of the fittest came to mean that the strong would survive and the weak would perish. However, fitness is just your ability to reproduce. It was never meant to go beyond that. Bonobos have a fitness that is almost certainly unique. Where males treat females like partners, where everyone is welcoming to immigrants and kind to strangers.

“One of the most special moments was when I was taking a photo of Izia crossing the river,” says Hilgartner. “She was standing in the river and so was I and she looked at me. She had her baby on her back, and when our eyes met, she was just so human.”

Few people take bonobos seriously. Bonobos have been celebrated and mocked as the ‘make-love-not-war’ hippie ape. They are often ignored as a freakish relative best left in the closet. But we ignore bonobos at our peril.

All females prefer males who are less aggressive. But only bonobo females have managed to turn this preference into a choice. And their choice is for tolerant males, who despite their size and strength, are still often submissive to a baby. In our large family of primates – and our even more close-knit great ape relatives – bonobos stand alone. Bonobos have escaped the lethal violence that threatens the rest of us. They do not kill each other. And that is a feat, that despite our intelligence, we have not yet managed to accomplish.

FIND OUT MORE

Discover more about the Bonobo Conservation Initiative at: bonobo.org