The remarkable ranging and meat-eating behaviour of the ‘make love, not war’ ape
For a couple of weeks now the bonobos on the east have been very difficult to find. It seems they have shifted their range considerably. For a long time they ranged between three main trails in the middle of the study area, called the golden triangle. Unfortunately, though, the days of the golden triangle are over. We are now more concentrating on the edges of the study area. Whenever we pick them up, the bonobos take us to little known areas in the south or in the east. We enter areas that have never been entered since the start of habituation two and a half years ago. This shift in ranging behaviour is probably triggered by scarcity of food sources. A similar pattern can be seen in the west community. These bonobos are currently using the far south and north of their range and even cross the Badzungu River going into the forest owned by the neighbouring village. Although a relatively small river, maybe ten meters wide with trees touching overhead at some places, the Badzungu is a big thing in this camp. To cross this river the bonobos, and the researchers following them, have to negotiate the extensive swampy areas along both sides.
A couple of weeks ago all members of the west community crossed the Badzungu to the west, leaving their normal home range unoccupied. However, the next day one of the visitors in camp came across bonobos in the middle of the usual home range of the west bonobos. The nest site was marked in the evening and we were all excited to know which bonobos had chosen this spot to spend the night. The next morning two west-side researchers went out expecting to find west-side bonobos. However, it turned out to be the bonobos from the east community who had crossed the Bompusa River to venture into the home range of the west community.Last Sunday I spent another afternoon following the fully habituated bonobos on the west. During the whole afternoon they were travelling in a fairly consistent southwestern direction feeding in several fruit trees on their way. At the end of the afternoon the bonobos were very dispersed in thick vegetation when all of a sudden we heard a nasal scream nearby. I immediately recognized the distress call of a duiker. All bonobos around us did hear it too and started running towards the source of the sound. Djaman and I did the same, climbing up a ravine and crawling through vines at full speed. At the other side of a little stream we found a female five meters in a tree holding a juvenile Weyns’ duiker (Cephalophus weynsi) screaming for its life. Several females were hanging around trying to get hold of the small forest antilope. In the commotion the female lost grip of her prey and the duiker fell to the ground five meters in front of us. The duiker was still making the repetitive distress calls, but its bones were probably broken and it did not move at all. Soon another female grabbed the animal and ran off followed by everyone, including us. A hundred meters further they started eating the duiker. A clump of several females accompanied by their offspring were all super excited trying to get a piece, while the males were watching the scene form a distance. The high-pitched screaming of the bonobos was deafening. After a female ripped off a leg the screams of the duiker ended. There were a lot of sexual contacts going on, especially females rubbing their genitals side by side, the bonobo way to reduce tension. Meat has the highest possible value in the bonobo society, so when available, everyone wants to get a share. These ‘make love, not war’ apes were enjoying the raw meat of a freshly killed duiker. The hands and teeth of one of the females were covered in blood. And she enjoyed it! After about an hour of excitement the group moved off and started to settle down for the night. The first individuals were building their nest, but when we left them at six o’ clock some of them were still busy getting the last pieces of meat out of the carcass.
Why do bonobos hunt? An interesting question. Meat-eating is well known from chimpanzees, but other primates, like the agile mangabeys (Cercocebus agilis) at Bai Hokou (Central African Republic) also hunt small duikers. It was very interesting for me to see this bonobo hunt and to compare it to the mangabeys’ behaviour. For chimps and bonobos hunting is a very social thing with a lot of food-sharing involved. In mangabeys only some adult males in the group hunt and these don’t actively share the meat with others. My guess is that the exceptional nutritional value of meat is the main reason why this behaviour evolved. However, sometimes you see bonobos and duikers peacefully walking next to each other. So why don’t they try to get every piece of meat in the forest? That’s when the social stuff comes in. Hunting may be a risky behaviour, especially if others are around who may want a piece of the cake too. Future studies might shed a clearer light on the evolution of this spectacular behaviour in primates.