White-eyelid mangabeys

Summary of a month and a half at LuiKotale

The sun is still shining at LuiKotale, but the solar system hasn’t been working properly for a while. Less energy means less battery on my laptop, so less opportunity to write a blog post. What follows is a summary of what happened in the last month and a half.

On the 6th of March I was planning an afternoon at ‘the viewpoint’. The window through the canopy is relatively small, but after a couple of months experiencing the claustrophobic forest, I really enjoyed being able to shed my eyes on a landscape that continues for more than a kilometer. On my walk to this viewpoint I stumbled upon a group of birds that were clearly disturbed by something. I tried but couldn’t determine the species, as the birds were behaving very agitated, jumping from branch to branch. At the same spot I noticed a Congo rope squirrel (Funisciurus congicus) reacting in the same way. All animals were focusing their eyes at the ground and it took me a while to realize that there was a rhinoceros viper (Bitis nasicornis) fifteen meters in front of me. This is one of the most deadly snakes in Central Africa, although they rarely attack.

March 20th was a special day. The east bonobos spent several hours in swampy areas in the southern part of their range. The group was steadily moving forward and we tried to keep up with them. I heard the agitated calls of a polyspecific group of monkeys ahead of us and I was just thinking: ‘this would be a good moment for a hunt’. That was exactly what happened! We didn’t see the actual chase, but we discovered an adult male holding a juvenile black mangabey (Lophocebus aterrimus), still alive. The presumably oldest and most dominant female in the group, Mayele, quickly took over the prey and several adult females followed her while she climbed a tree. We heard another party further north and I was wondering why these individuals didn’t come over to try to get a piece of the meat. When Mayele came down with the, in the meantime, dead mangabey, the whole party moved north towards the others. When we managed to catch up with them negotiating the lianas in this swampy forest, we saw another adult female with a small juvenile Wolf’s guenon (Cercopithecus wolfi). Two simultaneous monkey hunts, that’s what makes this community special! Hunting is known from several bonobo research sites, but LuiKotale is the only one where bonobos hunt primates, and the east community seems to do so more frequently than the bonobos in the west.
Last month the bonobos spent much time in swampy habitat. On the 22nd of March we started following the bonobos from their nest site near the center of their range. After feeding in a nearby fruit tree, the bonobos came down to the ground and started a march heading north. For more than two kilometer the community travelled continuously on the ground, feeding on the pith of Haumania shoots on the way. The bonobos ended up at the swamp along the Lokoro, the big river north of camp. The canopy becomes more broken, the undergrowth more dense, and the soil more wet, the closer you get to the river. In the end we were wading through thigh-deep water, crawling over vines and along clear elephant paths. This is tough habitat, but it was worth following the group up here.
The bonobos came specifically to this spot to strip the bark of several trees. They went from one tree to next licking the sap and scraping the trunk with their teeth to get the cambium. No one really knows why bonobos do this and what substances they get from it.
Our bonobos also went three times to the swamp along the Bompusa River separating the home range of the two communities that are being followed.
On March 29th we were able to follow them across the Bompusa. On the other side they fed in a Maku tree, just like they do everywhere and every day. After travelling south for more than a kilometer, we finally caught up with them and had some bonobos in sight. All of a sudden one of them gave a call and all bonobos ran over. It was clear that one individual found a good spot to cross the Bompusa and communicated this to the others. We finally lost them at the other side of the river. The other day one of the workers came back from the forest with a dead tree pangolin (Phataginus tricuspis) he found, and we decided to dissect it. The stomach was, not so surprising, filled with ants and termites. What mainly struck us was the very long, muscular tongue with supporting cartilage structures, which extended as far as the rectum. After the dissection we left the carcass in the forest with a camera pointing at it. To our surprise, the only carnivores that came, were the driver ants that totally ate the carcass within 36 hours.
The last notable event happened about a week ago. The west bonobos had been lost for almost a week, presumable ranging in the east or south more than 6 to 8 km away, when all of a sudden we heard them from camp! A couple of hours later the group came even closer and we could see them in the treetops at the edge of camp. The bonobos reacted nervously and were clearly not used to seeing and hearing the daily human life. I wonder what they were thinking…

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.

My dislike of snakes, elephants and mice explained

Due to some problems with our energy and mailing system, you had to wait a bit longer for an update from LuiKotale. As you can read in the next post to come, our bonobos on the east have been quite difficult to find last weeks. One day we were searching for traces on Jakobo, one of the trails in the south of the study area. This trail is not frequently used so it was locally overgrown with Haumania. That’s when a pair of shears comes in handy. While cutting a way through the Haumania, I accidently mistook a small greyish green snake for a Haumania stem and cut it. Indeed, you read it right, I cut a snake in the forest! Immediately I realized my mistake, dropped my shears and backed off while producing a fearful scream. I hate snakes! I really hate snakes, so I’m always wary ofthem in the forest. We don’t often see snakes, this was my fifth snake in two and a half months, and when encountering one they usually flee immediately. This was a rather close encounter as I cut the snake twenty centimeters from the head. I didn’t cut through, but the snake’s spinal cord was severely damaged and it couldn’t properly move anymore. Unfortunate for the snake, but it’s the price it has to pay for its supreme camouflage. The book in camp told us it was a forest vine snake (Thelotornis kirtlandii).

A lovely afternoon two weeks later. Lambert, my Congolese colleague, and I were searching for bonobos in the same area. We decided to split up to cover more ground listening for vocalizations. Lambert did the eastern loop while I searched in the west. We agreed to meet at a rendez-vous point before dark to head back to camp together. At 16:30 I reached one of the most southern locations where I heard bonobos far away. Disappointed about not being able to locate them, I was slowly walking back to the rendez-vous point. At 17:19 all of a sudden a giant forest elephant (Loxodonta cyclotis) was standing in the middle of the path in front of me! Wraaagh! I froze, screamed inside me and grabbed a small tree to hide (not that it could have offered protection, I think it was just my instinct). I didn’t run because the elephant saw me at the same time and it ran off through the forest with a thundering sound of breaking branches. My senses were in the highest state of alertness. I listened for the subtle sounds of more branches, footsteps, breaths, ear flapping, or any other sign of more elephants around. I only heard the elephant that had fled, heavily gasping for breath some fifty meters to the west. I walked further as silent as possible, counting 13 big steps to the spot where the elephant had been standing in a patch of boseki fruits (Irvingia gabonensis), but then I just ran off as fast as I could. Boseki trees, also known as forest mangoes, attract a lot of frugivores ranging from mangabeys and bonobos to red river hogs, yellow-backed duikers and elephants. Previous fieldwork has made me dislike elephants in the forest. This encounter was very exciting too, but luckily not with a scary ending, so in a way I’m happy this time to have experienced a real forest elephant in Congo. By the way, the third kind of animals I really dislike are mice. Probably that can be easily explained by the (genetically determined or socially transmitted?) mouse phobia of my mother. Whenever I see a mouse around our dining area or crawling along the onions in the depot, it frightens me to death.

To conclude, these three animals I don’t like are part of the ecosystem here at LuiKotale, and although we sometimes come across one, very rarely do they pose a real threat. I acknowledge this fact and actually, I’m a field biologist, so I like seeing animals, snakes, elephants and mice alike, but my mind just can’t prevent the initial expression of this deeply rooted fear response. And that is why my heart skips a beat whenever I see a snake, an elephant or a mouse.

PS: Since the beginning of the year we have seen several traces of elephants in the forest. We have had footprints as close as a kilometer from camp, fresh dung on the main trail and one or two elephants on the camera traps. My encounter was thus not so surprising.

One of the horrors of field work

Since about a week we have some visitors in camp, raising the number of white people to eleven. Camp life can be quite busy at times, especially because after more than ten years some major rearrangements in the camp infrastructure are being done. A new ten-meter long radio antenna has been installed with the help of half a dozen men, a roof collapsed as the workers were dismantling it pole by pole and houses are given new destinations and completely rebuilt during a single shift in the forest. These houses, most of them just shelters to put a tent underneath, are made of a wooden structure tied together using lianas covered with palm leaf roofing panels. All building materials come from the forest surrounding camp, so 100% ecologically certified.

Among the “visitors” is Gottfried Hohmann, one of the directors of the project. He brought in a good supply of goodies ranging from cinnamon to peanut butter. The first night we ate some leftover bread from Kinshasa. When your diet is rather limited in variation, one really appreciates the pleasure of eating something as simple as bread. Apart from the goodies he brought, Gottfried is particularly appreciated in camp because of his knowledge of bonobos. He is a good story-teller and when he shares his ideas at the dinner table everyone is listening and trying to absorb as much as possible.

Some days ago I experienced one of the horrors of the forest which many people fear. We left camp at 3:50 to arrive at the nest site at around 5:15 in the far south of bonobos’ range. The bonobos left their nest some ten minutes later and by 5:30 more and more individuals started eating in a nearby maku tree. It was still rather dark and we were trying to identify the first individuals. All of a sudden some bonobos quickly left the tree crown while others had not even entered it. Leanne had an insect in her hair and asked me to have a look at it. At the same time I felt something biting on my back, but I tried to help Leanne first. This became more and more difficult as I was bitten on my arms, head and hands by extremely fierce biting creatures. I thought we were standing above an ant nest from which the ants were falling down to protect their nest. It took us some time and a couple of meters running to realize we were being attacked by wasps! My guess is that the bonobos disturbed the nest in the tree, which made them leave the crown rapidly. I had a total of twelve stings, mostly on my head and hands, and Leanne had one. People have gone unconscious after only a few stings of these wasps as a result of an anaphylactic shock. I immediately took antihistamine and relied on the fact that I have never had a severe allergic reaction to bee or wasp stings. During the rest of the shift I could feel the pounding pain, although less extreme as I had expected, and the area around the stings started to swell gradually. We lost the bonobos during the wasp attack but found them again after a while. I couldn’t hold my binoculars properly and felt really tired, probably the combined effect of the adrenaline and the antihistamine, so I was not fully enjoying my time in the forest. However, the bonobos were showing some interesting ranging behaviour. They had nested the day before in the far south of their home range and in contrast to what one would expect, our bonobos only travelled south for more than two kilometers. When we entered the GPS track log in the file containing all follows since the beginning of habituation, the route of that day was clearly an outlier, not even crossed by any other track log ever recorded before. Why did they go there? Is it because of the current apparent difficulty of finding fruit? What would have happened if they would have bumped into the community inhabiting the south? Are they still hanging out in this southern area and does this explain our difficulty in finding them recently? Some interesting questions that can only be answered as habituation improves and we will be able to follow the bonobos for full days on end. It took us more than two hours, at a relatively slow pace, to get back to camp.

One of the pleasures of field work

For the rest of my stay in the field I am planning to do a small research project on the bonobo community in the east. Habituation level is not perfect, so we have to take some limiting factors into account, but it should be possible at this stage to collect the first detailed data.
To become more familiar with bonobo work, the possibilities of research and how people do it, Gottfried suggested that I should occasionally go to the fully habituated bonobos in the west. This community is being followed since 2002 and all individuals tolerate humans within ten meters. Yesterday, Sarah and I left camp around 11:00 after the morning team sent a text message to the camp satellite phone. Based on their location and direction of travel we predicted where we would find the bonobos. On our way we heard bonobos close by, but when Sarah produced a “whoop”, a two-syllable, two-tonal howl, the human version of a loud call to communicate over long distances, we didn’t get a response. We concluded that no one was following this party and we headed to the original location to try to do a proper hand-over. We were lucky. The bonobos hadn’t moved much in the meantime and we quickly got a whoop response, so we easily found the morning team. We were not extremely lucky, though, as this party contained only an adult female, Suzy, with her dependent daughter Salea, and a juvenile male called Hugo. Hugo is eight years old, but is not much bigger than Salea who is four. Hugo was born in this group, but left the study area a couple of years ago together with three other individuals at a time when poachers were thought to be active around. However, two years after this sudden incident, Apollo, a subadult male among the four who disappeared, showed up again carrying his brother Hugo on his back. Hugo’s mother has never been seen, and Apollo took over the care of his younger brother. Because of his early orphaning, he always lagged behind in his development.
Three individuals are not always easy to follow, but as long as we could keep up with this small party, we would be fine. “Bonobos always lead you to more bonobos”, Sarah said. After a first bit of travel, Suzy went up an emergent tree. She was sitting on a huge branch and tried to grasp it steadily so she could reach something below on the main trunk of the tree. When Suzy was hanging there in this acrobatic position with her daughter watching interested nearby, I saw a lot of bees flying around. A minute later she was licking the honey of her hands, clearly a highly valued food source. Bonobos’ closest relatives, chimpanzees (Pan troglodytes), also eat honey and the ones at Goualougo in the Nouabale-Ndoki National Park in the Republic of Congo use a complex set of tool to access it (you can see exactly how in one of the BBC series). About an hour later Suzy stopped at a small termite mound repeatedly picking something from the top. It was difficult to determine whethershe was eating termites or pieces of soil. Bonobos are known to feed on termites, but not to the same amount and especially not in the same way as chimpanzees do. Chimpanzees are well-known termite fishers. They pick a small twig, strip off the leaves and insert it in a termite hole to lick off the termites attached to the twig. It is a big mystery why bonobos don’t use tools when compared to chimpanzees. One possible explanation is that bonobos live in an environment that is rich enough and doesn’t necessitate extractive foraging like tool-use.
Eventually we lost our small party of three when they travelled through thick vegetation on the ground. Because we knew Niina was still around doing a full-day follow, Sarah whooped to try to get in touch. We got a double whoop response back, meaning that Niina was with bonobos. We took a compass bearing and started walking towards the source of the double whoop. After a hundred meters we reached a very steep ravine about ten to fifteen meters deep with a little stream running below. When we finally managed to climb to the other side, using a fallen log as a bridge, we soon came across a second, even deeper, ravine. I always highly appreciate discovering such hidden treasures in the forest, but they greatly slow you down when you need to get somewhere quickly. When we eventually reached the main trail on the west side we didn’t get a response to our whoops. We started walking along another trail, hoping we were heading in the right direction. Some 500 meters further we finally caught up with Niina and the big party she was following, including Suzy, Salea and Hugo. The bonobos were travelling terrestrially eating the young shoots and pith of Haumania on their way. For those who are not familiar with Haumania, Wikipedia might tell you that it is considered as terrestrial herbaceous vegetation (THV). You are now probably thinking of a small, lovely herb on the forest floor, but herbaceous just means that this plant is not a tree and does not contain lignin. Haumania has long stems, some of which grow vertically, and often forms very dense tangles. Bonobos go for Haumania shoots, especially in the afternoon, probably for its high protein content. The group was travelling north and when we got to a dense Haumania patch we got separated from Niina. When we got to the other side we lost the bonobos out of sight and soon we were even out of whooping distance from Niina. Bonobos can be very hard to follow as they decide to head straight towards a certain spot at full speed. We caught up with Niina and the bonobos about half an hour later at their last feeding tree for the day. A couple of minutes after we arrived, individuals started to come down, travelling further northeast. It felt so amazing to see dozens of bonobos coming down to the ground, walking ten meters from you, totally ignoring you, doing their thing. We walked along with them, crossed a trail, which the bonobos decided to follow. At normal walking speed we were following behind some individuals, while the rest of the group was behind us on the trail. Finally the bonobos arrived at their sleeping site and started building their nests at 17:45. Our small party had joined the bigger one and travelled almost five kilometers since we first found them at noon. What a wonderful afternoon, what a pleasure to spend a couple of hours near these apes who totally accept our presence around. This motivated me to keep up our work on the east to one day get to the same level of habituation.

Lieven in congo

At the moment Lieven Devreese is staying at LuiKotale, a bonobo research site of the Max Planck Institute for Evolutionary Anthropology in the vicinity of Salonga National Park, Democratic Republic of Congo. Lieven is a research assistant working on habituation of a second group of bonobos and he hopes to get to see some golden-bellied mangabeys as well. Here you can read more about his 10-month adventure.