The process of Chimpanzee habituation
Image © Paco Bertolani
Dr. Paco Bertolani, as mentioned in the previous blog post, will be at the forefront of the project to habituate the wild-born descendants of the chimps released on Rubondo Island in the 1960s.
Chimpanzees in the wild have a deeply ingrained fear and mistrust of human beings, and at the first sight of an approaching person they will flee immediately. “However, some people think that this fear for humans is the direct consequence of some previous bad experiences with humans, i.e. hunters.” Says Dr. Bertolani. “This idea is somehow supported by the fact that in very remote areas where it is likely chimpanzees have never seen humans, the chimpanzees seem more fearless than in other places. Unfortunately these remote areas do not exist anymore, thus this hypothesis is basically impossible to test. It is correct that all wild chimpanzees fear humans, but whether this fear is innate or learned we don’t really know.”
This makes the process of studying their behaviour in a natural state extremely difficult- until they have become habituated to the presence of humans; it is impossible to closely observe them.
Dr. Jane Goodall was the first person to acclimatise a community of chimps in the 1960s in Gombe Stream in Tanzania. As described in her book In the Shadow of Man, she spent many frustrating months attempting to get closer to the Kasakela chimpanzee community in order to study them.
In his experiences of habituation processes in Taï National Park in Côte d’Ivoire, Dr. Bertolani has made some interesting observations in how this is achieved, utilising known social behaviours and primate psychology.
“It is best to approach a party of chimpanzees alone, and to sit quietly in a visible place at a distance that the chimps feel comfortable with,” he says, “ this allows them to see you from the safety of their comfort zone.” By displaying a non-threatening posture, wearing drab clothing, moving slowly and maintaining the maximum distance to keep them in sight, the apes can gradually become more accustomed to seeing a human. “In dense forest however, this can be extremely difficult as visibility in this habitat is poor, leading to the chimps being surprised when sighting a person, and immediately fleeing.”
This is one of the reasons the process of habituation is extremely time-consuming and frustrating, taking years to achieve in every instance.
Mike Wilson, former director of field research at Gombe Stream Research Centre, wrote: “The general rule of thumb is that each individual primate needs about 100 hours to get used to people. In species that travel in cohesive troops, like baboons, every member of the group can see you every time you make contact, so the 100 hours go by fairly quickly, about 3 months. Chimpanzees take longer to habituate, because the entire social group rarely comes together. Individual chimpanzees often travel alone or in small subgroups, so it can take many years for every member of the group to become habituated. In forest sites, such as Kibale National Park in Uganda or Taï National Park in Côte d’Ivoire, habituation of chimpanzees without provisioning [feeding] has taken 5 or 6 years. Habituation may take even longer in savanna sites such as Semliki, Uganda, where chimpanzees range over huge areas and only rarely encounter researchers.”
“It was thought that savannah chimpanzees were impossible to habituate, but Fongoli chimpanzees in Senegal became habituated in a relatively short time, even when compared with forest chimpanzees elsewhere. We are talking four or five years, but the Semliki chimpanzees are still not habituated.” Says Br. Bertolani.
As recorded by Dr. Goodall, the first chimpanzee to tolerate her was a male that she named David Greybeard. In order to do this, she set up a feeding station that attracted him, and then eventually another male, Goliath. This approach has subsequently been criticised, but at the time, it was the only thing that worked.
“Usually a male will be the first to become tolerant of a human presence,” Dr. Bertolani notes, “as they are normally bolder by nature. What you then hope to achieve is to use this male’s tolerance to influence the rest of the community. The next step is to habituate females, who are naturally more wary and protective of their offspring.”
What happens next is reliant on ingrained biological urges that occur when hormones take over: “When a female comes into oestrus, males seek them out in order to mate, and this is where we hope that she will be followed by a male that is comfortable with a human presence. If the male is relaxed, she will overcome her natural fear in order to present to the male.” He says.
This interplay of hormonal biology and psychology has been the keystone to success on many occasions, where once a female tolerates an observer’s presence, she could pass on this behaviour to her offspring, but this is not always the case. In some instances, mothers have been habituated, but their juvenile offspring have not, or vice versa.
This is the enormous task that awaits Dr. Bertolani on Rubondo Island: to habituate a community of chimps that have all been born in the wild. “This is my primary goal, with the secondary aim being to directly observe them in a natural state once this has been achieved. There are many questions related to this community that I would like to discover the answers to.”
To read Dr. Bertolani’s paper on habituation in Taï National Park, click here