A day in the life of a habituator

People also celebrate Christmas and New Year in Congo. On Christmas, we had a relaxing day in camp with pancakes in the morning, chilli con carne with bread at lunch and calzone with chicken for dinner. We made a bit too much food and since we of course don’t have a fridge here, everyone had to do an effort to finish it. On New Year’s Eve, all local people had left camp to celebrate “la fête” in the village. We enjoyed the quietness in camp and the bean and rice burgers with guacamole and delicious little breads. All of that made on a simple wood fire with simple ingredients, it was just heaven.

For the rest of this post I want to tell you a bit more about my work as a habituator. Habituation is a term used in primatology for the process of accustoming wild animals to the presence of observers. It is defined as the relatively persistent waning of a response as a result of repeated stimulation that is not followed by any kind of reinforcement. In other words, repeated neutral contact between wild primates and human observers leads to a reduction in fear, and ultimately the ignoring of the observers. Habituation is a necessary step for the detailed study of ecology and behaviour in the wild. Observing primates directly without having an influence on their behaviour can learn us much about how they really are. Some species are more difficult to habituate then others. Species exhibiting wide-ranging behaviour, or species that don’t leave a lot of traces, are difficult to find and hence, difficult to habituate. Semi-terrestrial species or those living in dense habitats are not easy subjects either, as individuals will flee before you come close enough to observe them. For habituation to succeed, one needs to make repeated contact with the same individuals. Therefore, species with a fission-fusion social system or groups of very large size are again difficult to habituate. Great apes, along with mandrills (with groups of up to 800 individuals) and the semi-terrestrial white-eyelid mangabeys, are among the most difficult to habituate. You need an investment of several years and a lot of patience for bonobo habituation to be successful.

Yesterday Lovis, one of the local trackers, went into the forest in the afternoon to try to locate the nest site of a bonobo party by listening for their vocalizations. After dark, he arrived back in camp and gave us the location. Our bonobos were “nested” that evening, so I went to bed around 19h30. The next day we left camp at 4h00 for a 1-hour walk. We arrived on time at Bompusa 3250, where Lovis had pulled a cotton thread from the nest site to the trail. We backtracked the string of 90m, an easy one, to reach the trees where the bonobos had built their sleeping nests the evening before. It was 4h59 and, quite unusual, some bonobos were already awake. Not because of our arrival, but maybe the bright moon made them decide to leave their nest half an hour earlier than usual. At 5h24 one of the last bonobos left his nest and headed to a maku tree fifty meters further. Bonobos eat maku fruits year-round and almost every day. After a quick breakfast the individuals we were observing joined the ones thirty meters ahead in another maku tree. At 6h03 the whole party started moving further south and it was difficult to follow them. The individuals in our community are not yet fully habituated. When you approach them within 10 or 15 meters, they will move on, which makes it difficult to follow them on the ground. Luckily, bonobos vocalize regularly to make contact with other parties in the surroundings. So after we lost them for fifteen minutes, we found them again at 6h24 at one of their current favorite feeding trees about 300 meters further southwest. They were now feeding in a gigantic bopfunga tree of over 40 meters high. The thick and high canopy made it difficult to see who was in the tree, but fruits came down continuously, which indicated there were several individuals. After some resting, the party started to move to another tree at 7h24. With my binoculars I could see them all taking the same route along some lianas. I noted three adult males and several adult females of which I could recognize two. Some individuals have a very distinct face or have some missing toes or fingers, but for adult females we mainly use the size and shape of the sexual swelling to distinguish them from one another. Bonobos have sexual swellings to advertise their sexual receptiveness to males, just like chimpanzees, baboons, macaques, mangabeys and other species do. When they are feeding high up in a tree, this swelling is the most useful feature to recognize the females. After feeding in an unkown pod tree nearby from 7h30 to 7h47, the party descended to the ground and climbed the steep hill further to the south. We lost them out of sight, but stuck to the south-western bearing they were following. We listened on our way for branches moving or fruits coming down a tree, but without success. When we stopped near a tree fall at 8h14, we heard a soft weeping call and the smacking sounds of bonobos grooming each other. At times bonobos can be very quiet. The party we were following had settled down on the tree fall and was enjoying the beautiful morning. When they left the scene at 8h28, it was not clear to us in which direction they had gone and we didn’t see them again for the rest of the morning.

Habituation of wild animals entails certain risks, mostly for the animals. During the habituation process the level of stress caused by our presence is of course considerable, but this decreases as habituation continues. Even when habituation is complete, there is the risk of disease transmission, from humans to the habituated primates. That is why we always wear surgical masks when near the bonobos and why we don’t enter the forest when feeling sick. A simple cold can cause a severe infection and ultimately death among wild great apes and we definitely want to avoid that.

Around camp we have several “camp pets”, wild animals which are passively habituated to our presence in and around camp. In the forest office a bit further in the forest, you can regularly see blue duikers (Philantomba monticola) who walk slowly past. They know we are there, but don’t seem to bother about that human being sitting in a chair or lying in a hammock. I have had a male-female pair at three meters from me. At night we may come across a brush-tailed porcupine (Atherurus africanus) or a water chevrotain (Hyemoscus aquaticus) near our garbage bin and near the toilet an African civet (Civettictis civetta) is often seen. It always feels special to meet these fearless animals in our normal living space.

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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.